WO2002010133A1 - Tridentate ligands and their complexes with transition metals - Google Patents

Abstract

Tridentate ligands having the following formula (IV): wherein the various symbols have the meaning specified in the description, form relatively stable complexes with transition metals of groups 8 to 10 of the periodic table, which can be advantageously used as catalysts in the (co) polymerization of α-olefins, and especially ethylene, combined with a suitable co-catalyst, such as, for example, an aluminoxane or a fluororayl salt of boron.

Description

TRIDENTATE LIGANDS AND THEIR COMPLEXES WITH TRANSITION METALS .

The present invention, relates to new tridentate nitro- t genated ligands and their metallic complexes with transition metals.

More specifically, the present invention relates to said nitrogenated ligands which can form complexes with transition metals, especially of groups 8 and 9, and the use of these in catalytic compositions suitable for the

(co) polymerization of α-olefins within a wide range of temperatures and pressures.

It is generally known in the art that ethylene, or α- olefins in general, can be polymerized or copolymerized by means of low, medium or high pressure processes with heterogeneous catalysts based on a transition metal of groups 4 to 6 of the periodic table of elements (in the form approved of by IUPAC and published by. "CRC Press Inc." in 1989, to which reference will be made hereafter with the term "periodic table") , generally known as Ziegler-Natta type catalysts.

A more recent group of catalysts active in the polymerization of α-olefins consists of the combination of an oligomeric organo-oxygenated derivative of aluminum (in particular methylaluminoxane or MAO) with an η⁵-cy- clopentadienyl compound (metallocene) of a transition metal of the same groups 4 to 6 of the periodic table, and especially group . These latter catalysts are substantially soluble in hydrocarbon solvents and for this reason are of- ten defined as "homogeneous", even if their use is not limited to "homogeneous" processes, but can be extended to polymerization processes in heterogeneous phase, making the complex itself insoluble by supporting it on an inert solid material . The characteristics of polymerization processes based on this type of catalytic systems can substantially differ from those of processes using heterogeneous catalysts of the Ziegler-Natta type, to such an extent that new olefinic polymers can be obtained, in certain cases, which could not be prepared with the traditional systems . Among the numerous publications available in literature on the matter, reference is made, for example, to the publications "Progress in Polymer Science", vol. 20 (1995), pages 309- 367, and "Journal of Molecular Catalysis A: Chemical", vol. 128 (1998) , pages 1-331, for a wide range of applications of the above techniques and results obtained. In the continuous attempt to improve the state of the art, new catalysis methods have been recently proposed for the polymerization of α-olefins based on complexes of "heavy" transition metals, i.e. of groups 8 to 10 of the periodic table .

Oligomerization processes of olefins in the presence of nickel complexes have already been known for some time but it has rarely been possible to obtain high olefinic polymers with a catalysis based on this metal, as indi- cated, for example, in European patent 558,143.

Subsequently, international patent application WO

96/23010 described complexes of Pd(+2) or Ni(+2) with 1,4-

N,N-1, -diphenylbutadiene (DAB), or other ligands deriving therefrom, having the following characteristic structure (I) :

Ar

Ar

wherein each Ar group is a phenyl group optionally substituted with hydrocarbyl radicals, which, combined with typical activators of etallocene complexes, such as MAO mentioned above, or ionic activators more recently developed, based on tetraphenylboron salts, are capable of homo-polymerizing ethylene to surprisingly give a branched product, or co-polymerizing ethylene with other α-olefins, with non-conjugated dienes and with α,β- unsaturated polar organic compounds such as acrylates . In spite of a significant improvement with respect to the prior known art, the molecular weights obtained are still unsatisfactory for various industrial uses. It has been observed, however, that with this group of catalysts, the molecular weight of the polyethylene produced increases with the increase in the steric hindrance of the substitu- ents on the two aromatic groups bound to the nitrogen atoms.

Polymerization catalysts have also been proposed, according to international patent application WO 98/27124, comprising iron and cobalt complexes with nitrogenated tri- dentate chelating agents (TRI) having the following general formula (II) :

wherein each "R" group generally consists of an aromatic radical substituted by alkyl groups with a high steric hindrance, such as, for example, iso-propyl, tert-butyl, etc. For example, the following structure (III) of a ligand is provided for the preparation of cobalt or iron complexes suitable for the polymerization of ethylene:

wherein: R' = H or CH₃. These ligands can form catalysts having a certain polymerization activity also in situ, i.e. if charged into the polymerization reactor as such, in the presence of suitable Fe or Co metal salts. For example, it is described that by charging Co(acac)₂ + (III) + MAO (or MMAO) into a reactor in the presence of ethylene, the formation of polyethylene is observed even though there is a modest catalytic activity.

It is reported that the molecular weight control of the polymer obtained with said catalysts critically depends on the steric hindrance of the R_x and R₅ groups of each phenylimine group . Higher molecular weights are obtained with substituents with a greater hindrance. However, compared with those obtained with traditional catalytic systems, the olefinic polymers produced, under comparative conditions, with the above catalytic systems, still show decisively low, polydispersed molecular weights, which are such that the mechanical and rheological properties required for typical industrial uses such as the production of films or sheets, cannot be reached. The literature, the publication "Inorganica Chimica Acta", Vol.174 (1990), pages 9-11, also cites other trini- trogenated complexes of rhodium or iridium with 2,6- pyridinecarboxyaldehyde-bis- (2, 6-diisopropyl) alkylimines, as hydrogenation catalysts for hydrogen transfer. In these complexes, the imine groups, always the same, are of the benzyl type, instead of aryl. In the publication "Journal of the American Chemical Society", Vol. 121 (1999) page 9318, Gambarotta describes the 2, 6-diisopropylimines as vanadium complexes for the polymerization of ethylene. As far as the applicant knows, the trinitrogenated complexes of "heavy" transition metals cited in literature for use in the (co) polymerization of ethylene, are symmetrical and all substituted on the phenylimine ring with sterically hindered groups . The Applicant has now surprisingly found that complexes with trinitrogenated ligands of metals of groups 8 to 10 of the periodic table, substituted with aliphatic alkyl groups on an imine nitrogen atom, are unexpectedly capable of polymerizing ethylene with different and improved procedures and results with respect to what has been de- scribed so far in the art.

A first object of the present invention therefore relates to an organic compound suitable as neutral ligand of metals in an oxidation state different from zero, consisting of a di-imine of 2, 6-diacylpyridine (abbreviated DIAP), having the following general formula (IV) :

wherein:

R' and R' ' may independently be hydrogen or a hydrocarbon radical, preferably aliphatic, having from 1 to 10 carbon atoms, optionally halogenated, more prefera- bly methyl or ethyl,

S¹, S² and S³ each independently represent a substitu- ent of the pyridine ring selected in the group consisting of hydrogen, halogen and linear or branched alkyl or aryl groups, having from 1 to 15, preferably from 1 to 8, carbon atoms, optionally functionalized or joined to each other to form one or more condensed cycles with the pyridine ring; each of the R¹ and R² groups is independently a Cx-Cis alkyl group or a C₆-Cι₈ aryl group, optionally substi- tuted, on the condition that one of the R¹ or R² groups is alkyl and the other is aryl.

A second object of the present invention relates to a complex of the metal M selected from transition metals of groups 8 to 10 of the periodic table of elements, in an oxidation state different from zero, comprising a neutral ligand coordinated to the metal M consisting of a di-imine of 2, 6-diacylpyridine (abbreviated DIAP) included in the previous formula (IV) .

Said complex consequently has the following general formula (V) :

or also (DIAP)M(X)_n, in abbreviated form, wherein: DIAP means diacyliminopyridine and corresponds to a ligand having formula (IV) , coordinated to the metal M,

R' , R'', R¹, R², S¹, S² and S³ independently have any of the meanings attributed to the corresponding symbols in the compound having the previous formula (IV) , on the condition that the R¹ and R² groups are different from each other, and one is an alkyl radical and the other is an aryl radical;

M is a metal selected from transition metals of groups 8 to 10 of the periodic table, and is preferably Fe and Co, in an oxidation state "s" which is positive and different from zero, generally from 1 to 4, depending on the metal M in question; each X is independently a group of an anionic nature bound to the metal as anion in an ionic couple or with a "σ" type covalent bond; and "n" expresses the number of X groups sufficient to neutralize the formal "s" oxidation charge of the metal M, and is equal to "s" if all the X groups are monovalent.

Said di-imine of a diacylpyridine having formula (IV) , suitable as a neutral ligand of transition metals in the complexes having formula (V) , is therefore characterized by the presence of R¹ and R² organic groups or radicals, of a different structure, substituting the two imine nitrogen atoms. One of these groups is an aryl group, i.e. bound to the imine nitrogen by means of a carbon of an aromatic ring, whereas the other is an alkyl group, i.e. bound to the imine nitrogen by means of an aliphatic carbon atom, possibly optically active. In particular, it is preferable for one of the two ligands to have a high steric hindrance, and the other, on the contrary, to be relatively small and mobile. When R¹ or R² are aromatic groups, they preferably have the following formula (VI) :

In this formula, the different R₃, R , R₅, R₆ and R₇ groups, abbreviated R± (i = 3,..., 7), are independently hy- drogen, halogen, especially fluorine, or hydrocarbyl groups having from 1 to 15 carbon atoms. In the case of hydrocarbyl groups, substituted groups are not excluded from the scope of the present invention, provided they have functions incapable of chemically reacting (substantially in- ert, for example halogens) with the components of the catalytic systems comprising said complexes having formula (V) and of the processes catalyzed thereby.

Although a wide selection of possible Ri substituents is available to experts in the field, a preferred aspect of the present invention consists in the selection of at least one R₅ or R₆ group from hydrocarbyl radicals, preferably alkyl, especially when branched, such as methyl, isopropyl, s-butyl, t-butyl, benzyl, or aryl such as phenyl or 4- methylphenyl, to give the imine substituents a greater steric hindrance which determines the space configuration. These radicals are more preferably selected from methyl and cyclic or branched hydrocarbon groups having from 3 to 12 carbon atoms, and may be, for example, methyl, s-butyl, isopropyl, ter-butyl, cyclohexyl, phenyl, etc. The R₃, R₄ and R₇ radicals of the aromatic group having formula (VI) may independently represent an aliphatic alkyl group having from 1 to 4 carbon atoms, and are more preferably all methyl or hydrogen.

According to a particular aspect included in the scope of the present invention, adjacent Ri groups may be optionally further chemically bound to each other to form a cyclic structure condensed to the aromatic ring of the imine group, such as for example, if the group having formula (VI) is a naphthalene group. Alkyl groups suitable as R_x or R₂ groups in accordance with the present invention are generally all groups having from 1 to 15 carbon atoms bound to the nitrogen atom in formula (IV) with a non-aromatic carbon atom. This definition therefore comprises linear or branched aliphatic groups such as, for example, methyl, propyl, isopropyl, hexyl, sec-butyl, t-butyl, 5-methylhexyl, 4-ethylhexyl, n- nonyl, n-decyl and 2-butyloctyl . Also included in this definition are cyclic aliphatic groups such as, for example, cyclohexyl, hexamethylcyclohexyl, pentamethylcyclopen- tyl, cyclohexylmethyl and 2-cyclo-octylethyl. Other suit- able alkyl groups are those substituted with one or more aromatic groups such as benzyl, 2-phenylethyl, 1- phenylethyl, 2- (2, 6-dimethylphenyl) ethyl and so on.

Preferred R¹ or R² alkyl groups are methyl and alkyl groups which are branched or substituted with an aromatic or cycloaliphatic group having from 3 to 10 carbon atoms.

Examples of these preferred groups are methyl, isopropyl, t-butyl, benzyl, cyclohexyl, cyclohexylmethyl.

The R' and R' ' groups of the ligand having formula (IV) are preferably alkyl groups having from 1 to 5 carbon atoms, more preferably methyl.

The groups substituting the pyridine ring S¹, S² and S³ are preferably selected from hydrogen and short-chain al- kyls, more preferably hydrogen. According to a particular aspect of the present invention, however, these S¹, S² and S³ groups can be functional- ized with groups suitable for reacting with solid carriers, organic or inorganic, in order to obtain said ligands having formula (IV) or said complexes having formula (V) in supported solid form, which can be conveniently used in polymerization processes in heterogeneous phase, especially gas phase. Alternatively, these functional groups may be situated, according to the present invention, on one of the substituents of the aromatic group having formula (VI) , as mentioned above. The ligands having formula (IV) can be prepared using as precursor, a diacylpyridine with a suitable structure, in particular having the pre-selected substituent groups corresponding to the R' and R' ' groups in formula (IV) of the desired ligand. Said diacylpyridine is reacted, preferably in a solution of an inert organic liquid, more preferably selected from halogenated hydrocarbons, aromatic hydrocarbons, ethers, esters, amides, alcohols, with an aniline substituted on positions 1 to 5 of the ring corre- sponding to the R₃, R₄, R₅, R₆ and R₇ groups in the compound having formula (IV) to be obtained, in the presence of a protic acid, preferably a carboxylic acid in a molar ratio of 0.1 to 0.5 with respect to the diacylpyridine, as reaction catalyst . The reaction is carried out at temperatures generally ranging from 0 to 60°C, preferably from 10 to 40°C, using molar ratios between the diacylpyridine and aniline usually ranging from 2/1 to l/l. Ratios lower than 1 are generally less convenient. The reaction times normally range from 1 to 24 hours, more preferably from 1 to 8 hours. The solvent is preferably an alcohol.

An intermediate consisting of a mono-imine of a diacylpyridine, is thus obtained. This is separated from the excess diacylpyridine and from the other non-reacted components, and is reacted, under conditions similar to those mentioned above, with an aliphatic amine having a structure which is suitable for obtaining the desired compound having formula (IV) .

The compound having formula (IV) is thus obtained, by means of a subsequent formation process of the two imine groups, and is then separated and purified using the normal methods of organic chemistry appropriate for the purpose .

The compound having formula (IV) in turn forms an intermediate in the preparation of the above metallic complexes having formula (V) , in which it is present as neu- tral ligand coordinated to the metal M.

The ligands having formula (IV) form, as already mentioned, relatively stable complexes with transition metals, i.e. metals of groups 3 to 12 of the periodic table of elements. In particular, advantageous results in terms of po- lymerization catalysis of olefins can be obtained with complexes of groups 8 to 10, as specified with the previous formula (V) .

The complexes having formula (V) should be considered, according to the present invention, as being in any physi- cal form, such as, for example, isolated and purified solid form, solvated in a suitable solvent, or supported on suitable organic or inorganic solids, preferably having a granular or powder physical form.

The following terms are used hereinafter in the pres- ent description with the meaning specified below: " (co) polymerization", with reference to α-olefins, comprises both the homo-polymerization and co- polymerization of ethylene and/or other α-olefins with more than two carbon atoms, with each other or with another ethylenically unsaturated polymerizable compound;

"co-polymer of", when referring to a certain α-olefin, means that said copolymer contains at least 20% in moles of monomeric units deriving from said α-olefin; - "polydentate" or "polyvalent", with reference to a substituent group, an ion, a ligand, an organic radical, indicates the presence of at least two functions, interactions, bonds or valences.

In accordance with the present invention, preferred complexes having formula (V) are those in which the metal M is selected from cobalt, iron, ruthenium, rhodium and irid- ium in oxidation states +2 and +3. Cobalt and iron in oxidation state +2 are particularly preferred.

The symbol X in formula (V) indicates groups (or lig- ands) of an ionic nature of the complex claimed. It is known that transition metals rarely form compounds and complexes of an exclusively ionic nature, as the bond between the metal and ligand is in many cases of an ionic-covalent or totally covalent nature. The symbol X in formula (V) therefore indicates ligands of an anionic nature, which are normally bound to the metal M with a bond of a mainly covalent nature. The term (X)_n generally indicates the group of ligands of an anionic nature, regardless of the effective number and type of said ligands X present in the compound having formula (V) . Complexes in which different X ligands are present, are included in the above definition. Polyvalent and polydentate (X)_n ligands are also included in the scope of the present invention, as, for example, in the case of oxalate, sulfate or phthalate groups. Examples of groups of (X)_n ligands of an anionic nature which can form compounds having formula (V) are hal- ides, especially chloride and bromide, sulfates, and acid sulfates, alkyl- and aryl-sulfonic groups, phosphates and polyphosphates, alkyl- and aryl-phosphonic groups, hydride, linear, cyclic or branched alkyl groups having from 1 to 15 carbon atoms, such as methyl, ethyl, butyl, isopropyl, iso- amyl, octyl, decyl, benzyl, cyclopentyl, cyclohexyl, 4- methylcyclohexyl, alkylsilyl groups having from 1 to 20 carbon atoms, such as for example, trimethylsilyl, trieth- ylsilyl or tributylsilyl, aryl groups having from 6 to 15 carbon atoms, such as phenyl or toluyl, alkoxyl or thioalk- oxyl groups having from 1 to 10 carbon atoms, such as meth- oxyl, ethoxyl, iso- or sec-butoxyl, ethylsulfide, carboxy- late or dicarboxylate groups, such as acetate, trifluoro- acetate, propionate, butyrate, pivalate, stearate, benzo- ate, oxalate, malonate, phthalate, or again, a dialkyla ide group having from 2 to 15 carbon atoms, such as dieth- ylamide, dibutylamide, or alkylsilyl-amide, such as bis (trimethylsilyl) amide or ethyltrimethylsilylamide, diva- lent organic groups such as trimethylene or tetramethylene, or the ethylenedioxy group.

Groups or ligands different from each other, if desired, can also be present, such as for example, a chloride and a carboxylate or alkoxide group. The X groups are pref- erably selected so that the complex having formula (V) is sufficiently soluble in the solvents used during the polymerization process, especially in the case of solution processes. In certain cases however the solubility of the complex is irrelevant, as in the case of supported complexes. In this latter case, the group of an anionic nature X can also be made of an anionic function chemically bound to the carrier.

To facilitate the production and conservation of the respective complexes, chorine, bromine, alkoxide and car- boxylate groups (having from 2 to 15 carbon atoms) are preferred X groups.

Figures 1 and 2 indicate, for purely illustrative purposes which however are non-limiting, the molecular structures obtained by processing the small-angle X-ray spectrum of two typical complexes in accordance with the present in- vention, i.e. respectively: figure 1 represents the molecular structure of the complex [N-methyl-N- ( (E) -l-{6- [ (2, 6-diisopropylphenyl- ethaneimidoyl] -2-pyridinyl}-ethylidene) amine] co- bait [II] dichloride; figure 2 represents the molecular structure of the complex [N-benzyl-N- ( (E) -l-{6- [ (2, 6-diisopropylphenyl- ethaneimidoyl] -2-pyridinyl}-ethylidene) amine] cobalt [II] dichloride. According to the present invention, the complex having formula (V) can be prepared by means of a simple and convenient process comprising contact and reaction, preferably in the presence of an inert liquid to facilitate molecular migration, of the above DIAP ligand having formula (IV) with a suitable salt of the metal M selected. For example, it is possible to start from the chloride of the metal M dissolved in an alcohol, such as butanol, or a polar ether, such as tetrahydrofuran (THF) , by the addition of the stoi- chiometric quantity of the pre-selected ligand, and separa- tion of the complex formed according to one of the normal methods known in the art such as, for example, crystallization or precipitation by means of a non-solvent, followed by separation by filtration or decanting. Owing to the great affinity of the compound having formula (IV) for forming complexes with transition metals, the desired com- plex having formula (V) is rapidly formed and with substantially quantitative yields already under bland temperature conditions. The following reaction scheme can be applied:

M(X)_n + DIAP -» (DIAP) (X)_n wherein the various symbols have the same meaning defined above for formula (V) .

The salt M(X)_n can be any suitable salt of the metal M, or, if desired, a mixture of salts, also of different metals when a mixture of complexes having formula (V) of different metals is desired. The most interesting results have been obtained with salts of metals of group 8 or 9 of the periodic table of elements. Typical salts suitable for the purpose are halides, especially chlorides and bromides, alcoholates, carboxylates, acetylacetonates, malonates, and analogous organic salts. Inorganic salts, however, such as carbonates and bicarbonates, etc. are also suitable for the purpose provided they are capable, according to what is known in inorganic chemistry, of interacting with the compound (DIAP) in the reaction environment in order to form a coordination complex. Salts in which M and X are those specified above, in general and in the preferred form, with reference to the complex having formula (V) , are particularly suitable for the purposes of the present invention.

Said complexes having formula (V) , however, can also be obtained by modifying a pre-existing different complex having formula (V) , for example, by means of the exchange of a ligand of an anionic nature with another: Of particular interest for the present invention, is the method for the preparation of complexes in which at least one X, and preferably at least two Xs, are alkyl groups having from 1 to 10, preferably from 1 to 5, carbon atoms, starting from the corresponding complexes having formula (V) wherein X is, for example, chloride, alkoxide, amide or carboxylate, by alkylation with a suitable alkylating compound selected from known compounds suitable for this purpose, for example, a magnesium alkyl, a magnesium alkylhalide, an aluminum alkyl or an aluminum alkylhalide.

This preparation method, as also the previous one, can in certain cases also be used in situ directly in the envi- ronment destined for the polymerization process of which the complex having formula (V) is a component of the catalytic system. This possibility forms a further advantageous aspect of the present invention, as described in detail hereunder . A further object of the present invention relates to a catalytic system for the (co)polymerization of α-olefins comprising at least the following two components, as such or combined with each other:

(A) a complex of a metal M selected from transition metals and lanthanides, preferably selected from metals of groups 8 and 9 of the periodic table of elements, particularly Fe, Co, Ru, Ir and Rh, defined by the previous formula (V) ; (B) a co-catalyst consisting of at least one organic com- pound of an element M¹, different from carbon, selected from the elements of groups 2, 12, 13 or 14 of the periodic table as defined above.

In particular, according to the present invention, said element M¹ is selected from boron, aluminum, zinc, magnesium, gallium and tin, more particularly boron and aluminum.

In a preferred embodiment of the present invention, component (B) is an organo-oxygenated derivative of aluminum, gallium or tin. This can be defined as an organic co - pound of M' , in which the latter is bound to at least one oxygen atom and to at least one organic group consisting of an alkyl group having from 1 to 6 carbon atoms, preferably methyl .

According to this aspect of the invention, component (B) is more preferably an aluminoxane. As is known, alu- minoxanes are compounds containing Al-O-Al bonds, with a varying O/Al ratio, obtained in the art by reaction, under controlled conditions, of an aluminum alkyl, or aluminum alkyl halide, with water or other compounds containing pre- determined quantities of water available, as for example, in the case of the reaction of aluminum trimethyl with aluminum sulfate hexahydrate, copper sulfate pentahydrate or iron sulfate pentahydrate. Aluminoxanes which are preferably used for the formation of the polymerization catalyst of the present invention are cyclic and/or linear, oligo- or polymeric compounds, characterized by the presence of repetition units having the following formula:

R₉

—(Al—0)—

wherein R₉ is a C_!-C₆ alkyl group, preferably methyl. Each aluminoxane molecule preferably contains from 4 to 70 repetitive units which are not necessarily all the same, but may contain different R₉ groups. Said aluminoxanes, and particularly methylaluminoxane are compounds which can be obtained with known organometal- ■ lie chemical processes, for example by the addition of aluminum trimethyl to a suspension in hexane of aluminum sulf te hydrate . When used for the formation of a polymerization catalyst according to the present invention, the aluminoxanes are put in contact with a complex having formula (V) in such proportions that the atomic ratio between Al and the transition metal M is within the range of 5 to 5,000 and preferably from 10 to 500. The sequence with which compo- nent (A) and the aluminoxane (B) are put in contact with each other, is not particularly critical.

In addition to the above preferred aluminoxanes, the definition of component (B) according to the present inven- tion also comprises galloxanes (in which, in the previous formulae, gallium is present instead of aluminum) and stan- noxanes, whose use as cocatalysts for the polymerization of olefins in the presence of metallocene complexes is known, for example, from patents US 5,128,295 and US 5,258,475. According to another preferred aspect of the present invention, said catalyst can be obtained by putting component (A) consisting of at least on complex having formula (V) , in contact with component (B) consisting of at least one compound or a mixture of organometallic compounds of M' capable of reacting with the complex having formula (V) , extracting from this, a σ-bound group X as defined above, to form, on the one side at least one neutral compound, and on the other side an ionic compound consisting of a cation containing the metal M coordinated to the ligand DIAP, and an organic non-coordinating anion containing the metal M¹, whose negative charge is delocalized on a multicentric structure .

Components (B) suitable as ionizing systems of the above type are preferably selected from voluminous organic compounds of aluminum and especially of boron, such as for example, those represented by the following general formulae:

[(Rc)_wH₄-w]^β[B(R_D)₄]^"; B(R_D)₃; [Ph₃C] ⁺» [B (R_D) ₄] ^"; [(R_c)₃PH]WB(R_D)₄r; [Li]⁺»[B(R_D)₄]^'; [Li] ⁺« [Al (R_D) ₄] ^"; wherein the deponent "w" is an integer ranging from 0 to 3 , each R_e group independently represents an alkyl or aryl radical having from 1 to 10 carbon atoms and each R_D group independently represents an aryl radical partially or, preferably, totally fluorinated, having from 6 to 20 carbon atoms.

Said compounds are generally used in such quantities that the ratio between the atom M' in component (B) and the atom M in the complex having formula (V) is within the range of 0.1 to 15, preferably from 0.5 to 10, more pref- erably from 1 to 6.

Component (B) can consist of a single compound, normally an ionic compound, or, especially when no X in the compound having formula (V) is an alkyl, a combination of this compound with an alkylating agent such as MAO, or, preferably, with an aluminum trialkyl having from 1 to 8 carbon atoms in each alkyl residue, such as for example AlMe₃, AlEt₃, Al(i-Bu)₃, according to what is specified above .

In general, the formation of the ionic-type catalytic system, in accordance with this latter aspect of the pres- ent invention, is preferably carried out in an inert liquid medium, more preferably hydrocarbon. The selection of components (A) and (B) , which are preferably combined with each other, as well as the particular method used, can vary depending on the molecular structures and result desired, according to what is analogously described in specific literature available to experts in the field for other complexes of transition metals with imine ligands, for example by L.K. Johnson et al. in the publication "Journal of the American Chemical Society, vol. 117 (1995), pages 6414- 6415, and by G. van Koten and K. Vrieze in "Advances in Or- ganometallic Chemistry, vol. 21, page 151".

Examples of these methods are qualitatively schematized in the list provided hereunder, which however does not limit the overall scope of the present invention:

(mi) by contact of a complex having the previous general formula (V) , wherein at least one ligand X is hydrogen or an alkyl radical, with an ionic compound whose cation is capable of reacting with one of said sub- stituents to form a neutral compound, and whose anion is voluminous, non-coordinating and capable of delo- calizing the negative charge; (m₂) by the reaction of a complex having the previous formula (V) with an alkylating agent, preferably an alu- minum trialkyl, used in molar excess of 10/1 to 300/1, followed by the reaction with a strong Lewis acid, such as for example, tris (pentafluorophenyl) boron in a more or less stoichiometric quantity or in slight excess with respect to the metal M; (m₃) by contact and reaction of a complex having the previous formula (V) with a molar excess of 10/1 to 1000/1, preferably from 100/1 to 500/1 of an aluminum trialkyl or an alkylaluminum halide represented by the formula AIR' ' '_mZ₃-_m, wherein R' ' ' is a linear or branched Cι-C₈ alkyl group, or one of their mixtures, Z is a halogen, preferably chlorine or bromine, and "m" is a decimal number ranging from 1 to 3 ; followed by the addition to the composition thus obtained, of at least one ionic compound of the type described above in such quantities that the ratio between B or Al in the ionic compound and the atom M in the complex having formula (V) is within the range of 0.1 to 15, preferably from 1 to 6. Examples of ionizing ionic compounds or multi- component reactive systems capable of producing an ionic catalytic system by reaction with a complex having formula (V) according to the present invention, are described, although with reference to the formation of ionic metallocene complexes, in the following publications, whose content is incorporated herein as reference: W. Beck et al., Chemical Reviews, Vol. 88 (1988), pages 1405-1421;

S. H. Stares, Chemical Reviews, Vol. 93 (1993), pages

927-942; -- Published European patent applications Nr.: EP-A

277.003, EP-A 495,375, EP-A 520,732, EP-A 427,697, EP-

A 421,659, EP-A 418,044;

Published international patent applications Nr. : WO

It has been found that the behaviour and reactivity of these ionic activator systems towards complexes having formula (V) is qualitatively analogous to that observed in the case of metallocene complexes of Ti and Zr used as catalysts in the polymerization of olefins. The specific char- acteristics of the catalytic system in accordance with the present invention should therefore be considered as being essentially due to the presence of the complex having formula (V) , or to the products deriving therefrom, during the formation of the activated catalytic system. Also included in the scope of the present invention are those catalytic systems comprising two or more complexes having formula (V) mixed with each other. Catalysts of the present invention based on mixtures of complexes having different catalytic activities can be advan- tageously used in polymerization when a wider molecular weight distribution of the polyolefins thus produced, is desired.

According to another aspect of the present invention, in order to produce solid components for the formation of catalysts for the polymerization of olefins, the above complexes can also be supported on inert solids, preferably consisting of oxides of Si and/or Al, such as, for example, silica, alumina or silico-aluminates. For the supporting of said catalysts, the known supporting techniques can be used, normally comprising contact, in a suitable inert liquid medium, between the carrier, optionally activated by heating to temperatures exceeding 200°C, and one or both of components (A) and (B) of the catalytic system of the present invention. For the purposes of the present invention, it is not necessary for both components to be supported, as it is also possible for only the complex having formula (V) , or the organic compound of B, Al, Ga or Sn as defined above, to be present on the surface of the carrier. In the latter case, the component which is not present on the sur- face is subsequently put in contact with the supported component, at the moment of the formation of the catalyst active for the polymerization.

Also included in the scope of the present invention are the complexes, and catalytic systems based on these, which have been supported on a solid by means of the func- tionalization of the latter and formation of a covalent bond between the solid and a complex included in the previous formula (V) .

One or more other additives or components can be op- tionally added to the catalytic system according to the present invention, as well as the two components (A) and (B) , to adapt it for satisfying specific requisites. The catalytic systems thus obtained should be considered as being included in the scope of the present invention. Addi- tives or components which can be included in the preparation and/or formulation of the catalyst of the present invention are inert solvents such as, for example, aliphatic and/or aromatic hydrocarbons, aliphatic and aromatic ethers, weakly coordinating additives (Lewis bases) se- lected, for example, from non-polymerizable olefins and sterically hindered or electronically poor ethers, haloge - ating agents such as silicon halides, halogenated hydrocarbons, preferably chlorinated, and the like.

Components (A) and (B) form the catalyst of the pres- ent invention by contact with each other, preferably at temperatures ranging from 20 to 60°C and for times varying from 10 seconds to 10 hours, more preferably from 30 seconds to 5 hours .

As mentioned above, the catalytic system according to the present invention is suitable, in its most general sense, for effecting any (co)polymerization process of α- ole ins, which in turn forms an object of the present invention. This can be carried out with satisfactory results with any combination of conditions normally used in polym- erization processes of α-olefins, owing to the specific activity and long duration of the catalytic system used.

The catalytic systems according to the present invention can be used with excellent results in substantially all known (co)polymerization processes of α-olefins, either in continuous or batchwise, in one or more steps, such as, for example, processes at low (0.1-1.0 MPa) , medium (1.0- 10 MPa) or high (10-150 MPa) pressure, at temperatures ranging from 20° to 250°C, optionally in the presence of an inert diluent. Hydrogen can be conveniently used as olecu- lar weight regulator.

These processes can be carried out in solution or suspension in a liquid diluent normally consisting of an aromatic hydrocarbon or an aliphatic or cycloaliphatic saturated hydrocarbon, having from 3 to 8 carbon atoms, but which can also consist of a monomer as, for example, in the known co-polymerization process of ethylene and propylene in liquid propylene. The quantity of catalyst introduced into the polymerization mixture is preferably selected so that the concentration of the metal M ranges from 10^""4 to 10^"8 moles/liter. Alternatively, the polymerization can be carried out in gas phase, for example, in a fluid bed reactor, normally at pressures ranging from 0.5 to 5 MPa and at temperatures ranging from 50 to 150°C. According to a particular aspect of the present invention, the catalytic system for the (co)polymerization of α- olefins is prepared separately (preformed) by contact of components (A) and (B) , and is subsequently introduced into the polymerization environment. The catalytic system can be charged first in the polymerization reactor, followed by the reagent mixture containing the olefin or mixture of olefins to be polymerized, or the preformed catalytic system can be charged into the reactor already containing the reagent mixture or, finally, the reagent mixture and the catalytic system can be contemporaneously fed into the reactor.

According to another aspect of the present invention, the catalyst is formed "in situ", for example by introducing components (A) and (B) separately into the polymeriza- tion reactor containing the pre-selected olefinic monomers and possible non-olefinic co-monomers. The use of this latter formation technique of the catalytic system should be appropriately evaluated by experts in the field to ensure that the contemporaneous presence of certain components re- active with each other, does not produce results which are different from those expected.

For example, the in situ preparation technique is suitable when component (A) is a preformed complex having formula (V) and component (B) is an organo-oxygenated com- pound of a metal of group 13, in particular an aluminoxane. Equally convenient, in terms of rapidity and facility in the preparation of the catalytic system, is the use of the in situ technique by the mixing, either contemporaneously or, preferably, in two subsequent steps, in the same reac- tion environment, of the DIAP ligand having formula (IV) , a suitable salt of the metal M(X)_n and aluminoxane, in the relative quantities specified above. The contact and reaction between a DIAP ligand, a salt of the metal M and an aluminum alkyl, or other alkylating agent, followed by the addition of a non-coordinating ionizing compound, for the preparation in situ of an ionic catalytic system in accordance, with the present invention, according to one of the general methods previously defined by "m₂" and "m₃", have proved to be less advantageous in certain cases, in terms of catalytic activity. In this case, it is preferable to preform the complex having formula (V) to be subsequently used for the optional preparation in situ by reaction with an aluminum alkyl (or other alkylating agent) and an ionizing compound. The catalysts according to the present invention can be used with excellent results in the polymerization of ethylene to give linear polyethylene and in the copolymeri¬

zation of ethylene with propylene or higher α-olefins, preferably having from 4 to 10 carbon atoms, to give co- polymers having different characteristics depending on the specific polymerization conditions and on the quantity and structure of the α-olefin. For example, linear polyethyl- enes can be obtained, with a density ranging from 0.880 to 0.940, and with molecular weights ranging from 10,000 to 2,000,000. The α-olefins preferably used as comonomers of ethylene in the production of low or medium density linear polyethylene (known as ULDPE, VLDPE and LLDPE depending on the density), are 1-butene, 1-hexene and 1-octene.

The catalyst of the present invention can also be con- veniently used in copolymerization processes of ethylene and propylene to give saturated elastomeric copolymers vul- canizable by means of peroxides and extremely resistant to aging and degradation, or in the terpolymerization of ethylene, propylene and a non-conjugated diene, having from 5 to 20 carbon atoms, to obtain vulcanizable rubbers of the EPDM type. In the case of these latter processes, it has been found that the catalysts of the present invention allow the production of polymers having a particularly high diene content and average molecular weight, under the po- lymerization conditions. The catalysts of the present invention can also be used in homo- and co-polymerization processes of α-olefins having at least 3 carbon atoms, according to the known techniques, giving, with excellent yields, atactic, isotac- tic or syndiotactic polymers, depending on the nature of the complex having formula (V) and type of monomer, α- olefins suitable for the purpose are those having from 3 to 20 carbon atoms, optionally also comprising halogens or aromatic nuclei such as, for example, propylene, 1-butene, 1-hexene, -methyl-1-pentene, 1-decene and styrene.

The present invention is further described by the following examples, which, however, are provided for purely illustrative purposes and do not limit the overall scope of the invention itself. EXAMPLES

The analytical techniques and characterization methods used in the following examples are listed below and briefly described.

The ^XH-NMR spectra were registered by means of a nu- clear magnetic resonance spectrometer mod. Bruker MSL-300, using CDC1₃ as solvent for each sample.

The I.R. spectra were registered by means of a Perkin Elmer 1600 spectrophotometer Series FTIR.

The RX reflectance spectrophotometry for the charac- terization of metal complexes according to the present in- vention, was effected with Beckman DK-2A Spectrophotometer.

The measurement of the molecular weights of. the olefinic polymers was carried out by means of Gel-Permeation Chromatography (GPC) . The analyses of the samples were ef- fected in 1, 2, 4-trichlorobenzene (stabilized with Santonox) at 135°C with a WATERS 150-CV chromatograph using a Waters differential refractometer as detector.

The chromatographic separation was obtained with a set of μ-Styragel HT columns (Waters) of which three with pore dimensions of 10³, 10⁴, 10⁵ A respectively, and two with pore dimensions of 10⁶ A, establishing a flow-rate of the eluant of 1 ml/min.

The data were obtained and processed by means of Maxima 820 software version 3.30 (Millipore); the number (M_n) and weight (M_w) average molecular weight calculation was carried out by universal calibration, selecting polystyrene standards with molecular weights within the range of 6,500,000-2,000, for the calibration.

The determination of the structures by means of X-rays of the new complexes according to the present invention was effected on a Siemens AED diffractometer.

During the preparations described in the examples, the following commercial reagents were used: 2, 6-diacetylpyridine FLUKA 2, 6-di-isopropylaniline ALDRICH 2-tert-butylaniline ALDRICH cyclohexylamine ALDRICH mesitylaniline ALDRICH (R) - (+) -methyl benzylamine ALDRICH (S)-(-)-(l-naphthyl) ethylamine ALDRICH diphenylmethylamine ALDRICH 1, 2-diphenylethylamine ALDRICH t-butylamine ALDRICH methyllithium (MeLi) 1 M in diethyl ether ALDRICH butyllithium (BuLi) 2.5 M in hexane ALDRICH methylalumoxane (MAO) (Eurecene 5100 10T,

10% by weight of Al in toluene) WITCO

Cobalt dichloride hydrate CoCl₂-6H₂0 ALDRICH

Nickel dibromide ALDRICH Iron dichloride tetrahydrate ALDRICH

The reagents and/or solvents used and not indicated above are those commonly and can be easily found at all commercial operators specialized in the field.

The various operations and purifications of the sol- vents and reagents were carried out in an inert atmosphere of nitrogen or argon, according to the technique normally used for the preparation and use of organic and organome- tallic compounds. Preparation of the "Intermediate A" product: l-{6-[(2,6- diisopropylphenyl) ethaneimidoyl] -2-pyridinyl}-1-ethanone [ (formula (VII) ]

1.630 g (10.0 mmoles) of 2, 6-diacetylpyridine are dissolved in 15 ml of ethanol and 1.70 ml (1.596 g, 9.0 mmoles) of 2, 6-diisopropylaniline and 0.15 ml of formic acid are added, under stirring. The mixture is left to react for 12 hours. The solid thus formed is filtered, and is then recrystallized from the ethanol solution, washed with methanol and dried in an oven under vacuum. 2.7 g of a pale yellow-coloured solid are obtained, which, after elemental analysis and I.R. and N.M.R. characterization, proved to consist of the desired product having formula (VII) (8.3 mmoles, yield 93%), having a molecular weight of 322.5 g/mole and a melting point of 183 °C. Elemental analysis: Calculated C: 78.22 H: 8.13 N: 8.69 Found C: 78.39 H: 8.17 N: 8.84

I.R.: V(C=N) 1648 cm^"1; V(_C=o) 1698 cm^"1;

^Η NMR (CDC1₃) : 1.16 (d, 6H, J_x=6.89 Hz); 1.17 (d, 6H, J_x=

6.89 Hz); 2.28 (s, 3H) ; 2.74 (sept, 2H, Ji=6.89 Hz); 2.81(s,

3H) ; 7.08-7.22 (m, 3H) ; 7.96 (m, 1H) ; 8.16 (dd, 1H, J_x=7.66 Hz, J₂=1.19 Hz); 8.58 (dd, 2H, J₁₌7.80 Hz, J₂=1.19 Hz). Preparation of the "Intermediate B" product: l-{6-[(2,6- dimethylphenyl) ethaneimidoyl] -2-pyridinyl}-l-ethanone [(formula (VIII)] .

0.490 g (3.0 mmoles) of 2, 6-diacetylpyridine are dissolved in 7 ml of methanol, 0.333 ml (0.327 g, 2.7 mmoles) of 2,6- di ethylaniline and 0.05 ml of formic acid are added and the mixture is placed in a refrigerator at 0°C for three days. At the end of this period, the presence of yellow crystals is observed, which are filtered and washed with cold methanol. 0.595 g of a crystalline solid are thus obtained, which, after elemental analysis and I.R. and N.M.R. characterization, proved to consist of the desired product having formula (VIII) (2.236 mmoles, yield 75%), having a molecular weight of 266.3 g/mole and a melting point of 118°C.

Elemental analysis: Calculated C: 76.67 H: 6.81 N: 10.53

Found C: 76.45 H: 6.54 N: 10.41

I.R.: V(_C=N) 1645 cm^"1; V(_C_=o) 1698 cm^"1;

^XH NMR (CD₂C1₂) : 2.02 (s, 6H) ; 2.22 (s, 3H) ; 2.76 (s, 3H) ; 6.89-6.97 (m, 1H) ; 7.05-7.10 (m, 2H) ; 7.96 (m, 1H) ; 8.10 (dd, 1H, Ji = 7 . 72 Hz , J₂ = 1 . 23 Hz ) ; 8 . 56 (dd, 2H, J_x ~- 7 . 72 Hz , J₂ = 1 . 23 Hz) .

Preparation of the "Intermediate C" product: l-{6-[(2-t- butylphenyl) ethaneimidoyl] -2-pyridinyl}-l-ethanone [(for- mula (IX)] .

The same procedure is adopted as for the "intermediate B" product, but using 0.426 g of 2-tert-butyl aniline (2.7 mmoles) instead of 2, 6-dimethylaniline.

0.332 g of a light yellow solid are obtained (m.p. = 166-167°C) corresponding to the desired product, on the basis of the following characterization:

Elemental analysis: Calculated C: 77.5 H: 7.53 N: 9.52

Found C: 78.0 H: 7.60 N: 9.65 IR spectra: two bands are present with the same intensity

centered at 1694.5 cm^"1 and 1644.5 cm^"1 attributed to v_(c=o₎ and V(_C=N) respectively.

^XH NMR (δ shift from TMS) : 1.39 (s, 9H) ; 2.41 (s, 3H) ; 2.80 (s, 3H) ; 6.54 (dd, 1H) ; 7.24 ( , 2H) ; 7.43 (dd, 1H) ; 7.95 (t, 1H) ; 8.13 (d, 1H) ; 8.50 (d, 1H) .

EXAMPLE 1 : Synthesis of N-{ (E) -1- [6- (cyclohexylethane- imidoyl) -2 -pyridinyl] ethylidene} -2 , 6 -disopropylaniline [formula (X) ]

0.170 g (0.53 mmoles) of intermediate A (formula (VII), obtained as described above) and 0.910 ml (0.789 g, 7.95 mmoles) of cyclohexylamine are charged into a 50 ml flask, together with a small quantity of CHC1₃ until the solid has completely dissolved, and the temperature is brought to 100°C. After 20 hours the excess cyclohexylamine is removed and the residue is crystallized from a small amount of cold methanol. 0.153 g of a yellow solid are obtained, which, after elemental analysis and I.R. and N.M.R. characterization, proved to consist of the desired product having formula (X) (0.38 mmoles, yield 72%), having a mo- lecular weight of 403.7 g/mole and a melting point of 188°C.

Elemental analysis: Calculated C: 80.34 H: 9.24 N: 9.87

Found C: 80.54 H: 9.37 N: 10.20

I.R. : V(C=_N) 1636 cm^"1 ^Η NMR (CD₂C1₂) : 1.16 (d, 12H, Ji = 6.87 Hz); 1.25-1.95 (m, 10H) ; 2.26 (s, 3H) ; 2.45 (s, 3H) ; 2.77 (sept, 2H, J_x = 6.87 Hz); 3.55-3.66 (m, 1H) ; 7.05-7.25 (m, 3H) ; 7.81 (m, 1H) ; 8.21 (dd, 1H, Ji = 7.80 Hz, J₂ = 1.06 Hz); 8.36 (dd, 2H, J_x = 7.80 Hz, J₂ = 1.06 Hz) . EXAMPLE 2: Synthesis of N- (2 , 6-diisopropylphenyl) -N- [ (E) -1-

(6-{ [ (IR) -1-phenylethyl] -ethaneimidoyl}-2 -pyridinyl) ethyl- idene] amine [formula (XI)]

0.170 g (0.53 mmoles) of intermediate A (formula (VII), obtained as described above) and 0.473 ml (0.450 g, 3.71 mmoles) of (R) - (+) -methylbenzylamine are charged into a 50 ml flask, together with a small quantity of CHC1₃ until the solid has completely dissolved. The temperature is brought to 100°C. After 18 hours the excess amine is removed, a small amount of methanol is added to the residue and the mixture is left at 0°C for 2 days. 150 mg of a pale yellow solid are obtained, which, after elemental analysis and I.R. and N.M.R. characterization, proved to consist of the desired product having formula (XI) (0.34 mmoles, yield 64%), having a molecular weight of 443.7 g/mole and a melting point of 93 °C. Elemental analysis: Calculated C: 81.83 H: 8.29 N: 9.87

Found C: 82.04 H: 8.47 N: 9.85

[α] _d (CHCl₃ , 298 K) + 1 . 9 ° C = 2 . 89

I . R. : V (_C-_HI) 1633 cm^"1; V_(C=_N2. 1644 cm^"1

^XH NMR (CDC1₃) : 1.14-1.19 (m, 12H) ; 1.58 (d, 3H, J_x = 6.64 Hz); 2.26 (s, 3H) ; 2.50 (s, 3H) ; 2.73 (m, 2H) ; 4.97 (q, 1H, Ji = 6.64 Hz); 7.07-7.77 (m, 8H) ; 7.85 (m, 1H) ; 8.36-8.39 (m, 2H) . EXAMPLE 3 : Synthesis of N- (2 , 6-diisopropylphenyl) -N- [ (E) -1-

(6-{ [ (IS) -1- (2-naphthyl) ] ethaneimidoyl}-pyridinyl) ethylid- ene] amine (formula (XII).

0.170 g (0.53 mmoles) of intermediate A (formula (VII), obtained as described above) and 0.33 ml (0.350 g, 2.04 mmoles) of (S) - (-) - (1-naphthyl) ethylamine are charged into a 50 ml flask, and a small quantity of CHC1₃ is added until the solid has completely dissolved. The temperature is brought to 100°C. After 17 hours 5 ml of methanol are added and the mixture is cooled to 0°C. 0.12 g of an off- white solid are slowly separated, which, after elemental analysis and I.R. and N.M.R. characterization, proves to consist of the desired product having formula (XII) (0.36 mmoles, yield 69%), having a molecular weight of 493.7 g/mole and a melting point of 68°C.

Elemental analysis: Calculated C: 83.32 H: 7.84 N: 8.83

Found C: 83.64 H: 7.82 N: 8.77

I.R. : V(_C=N) 1643 cm^"1

[α]_d(CHCl₃, 298 K) + 88.8° C = 1.57

^XH NMR (CD₂C1₂) : 1.10-1.17 (m, 12H) ; 1.72 (d, 3H, J_x = 6.51 Hz); 2.26 (s, 3H) ; 2.50 (s, 3H) ; 2.73 (m, 2H) ; 5.67 (q, 1H, Ji = 6.51 Hz); 7.03-7.20 (m, 3H) ; 7.45-7.77 (m, 7H) ; 7.88

(m, 1H) ; 8.32-8.43 (m, 2H) .

EXAMPLE 4 : Synthesis of N-{ (E) -1- [6- (cyclohexylethaneimid- oyl) -2-pyridinyl] ethylidene}-2, 6-dimethythaniline (XIII) .

A mixture of 0.131 g (0.49 mmoles) of intermediate B (formula (VIII), obtained as described above) and 0.485 g (4.9 mmoles) of cyclohexylamine is prepared in a Schlenk tube and the temperature is brought to 100°C until a pale yellow limpid solution is obtained. The solution is maintained at 100°C for 24 hours, after which most of the excess cyclohexylamine is removed by suction under vacuum. About 1 ml of CH₂C1₂ is added to the residue, the mixture is poured into 5 ml of methanol, heated to 80°C until an overall volume of about 2 ml is obtained, by evaporation of the solvent, and finally left to rest at -15°C for a fur- ther 2 days. The solid obtained is filtered, washed with methanol previously cooled to 0°C, and dried in an oven at 40°C under vacuum. 0.093 g of a greyish-yellow solid are obtained , which, after elemental analysis and I.R. and N.M.R. characterization, proves to consist of the desired product having formula (XIII) (0.323 mmoles, yield 66%), having a molecular weight of 347.5 g/mole and a melting point of 98°C.

Elemental analysis: Calculated C: 79.50 H: 8.41 N: 12.09

Found C: 79.78 H: 8.65 N: 12.15 I.R.: V(_C=N) 1634 cm^"1

^XH NMR (CD₂C1₂) : 1.25-1.95 (m, 10H) ; 2.01 (s, 6H) ; 2.20 (s,

3H) ; 2.42 (s, 3H) ; 3.55-3.66 (m, 1H) ; 6.88-7.08 (m, 3H) ;

7.81 (m, 1H) ; 8.18 (dd, 1H, Ji = 7.78 Hz, J₂ = 1.11 Hz);

8.34 (dd, 2H, J_x = 7.66 Hz, J₂ = 1.11 Hz) .

EXAMPLE 5 : Synthesis of [N-diphenylmethyl-N- ( (E) -l-{6-

[ (2 , 6-diisopropylphenylethaneimidoyl] -2-pyridinyl}ethylid- ene) amine (XIV) .

0.64 g of l-{6- [ (2, 6-diisopropylphenyl) ethaneimidoyl] - 2-pyridinyl}-1-ethanone (intermediate A having formula (VII), obtained as described above; 2.0 mmoles) are suspended in 20 ml of anhydrous ethanol. 0.65 ml of diphenyl- methylamine (3.8 mmoles), 20 ml of anhydrous THF and three drops of formic acid are added. The mixture is left to react at 20°C for 24 hours. 0.5 g of Na₂C0₃ are ^' added to the solution thus obtained to neutralize the formic acid. The filtered solution is concentrated under vacuum. A light yellow solid precipitates which is filtered and dried under vacuum at room temperature. 0.55 g of the desired compound having formula (XIV) are obtained, as confirmed after characterization.

Elemental analysis: Calculated C: 83.73 H: 7.64 N: 8.61

Found C: 83.1 H: 7.84 N: 8.54

EXAMPLE 6 : Synthesis of N-l, 2-diphenylethyl-N- ( (E) -l-{6-

[ (2, 6-diisopropylphenylethaneimidoyl] -2-pyridinyl}ethylid- ene) amine (XV) .

The same procedure is adopted as described in example 5, but using an equivalent molar quantity of 1,2- diphenylethylamine (3.8 mmoles) instead of diphenylmethyla- mine. At the end, 0.68 g of the desired compound (XV) are obtained, as confirmed after characterization. Elemental analysis: Calculated C: 83.96 H: 7.6 N: 8.4

Found C: 82.9 H: 7.99 N: 8.35 EXAMPLE 7 : Synthesis of [N-benzylyl-N- ( (E) -l-{6- [ (2-tert- butylphenylethaneimidoyl] -2-pyridinyl}ethylidene) amine (XVI) .

The same procedure is adopted as described in example 5, but using 3.8 mmoles of benzylamine and 0.59 g (2.0 mmoles) of intermediate C having formula (IX) . At the end of the reaction, after separation and washing, 0.63 g of the desired compound having formula (XVI) are obtained. Elemental analysis C% H% N%

81.4 7.6 10.9 theoretical 81.2 7.5 11.1 experimental EXAMPLE 8 : Synthesis of N- (benzyl) -N-{ (E) -1- [6- (2, 6- diisopropylphenylethaneimidoyl) -2-pyridinyl] ethylidene}amine (XVII) .

0.64 g (2.0 mmoles) of intermediate A (formula (VII), obtained as described above) are suspended, in a 100 ml flask, in 20 ml of anhydrous ethanol. 0.65 ml of benzylamine, 2 drops of formic acid and 20 ml of THF are added. The reaction mixture is left under stirring for 16 hours at room temperature, with the formation of a limpid solution. The solution is concentrated under vacuum until a light yellow solid precipitates, which is separated and washed with a small quantity of ethanol . 0.94 g of a pale yellow solid are obtained, which, after elemental analysis and N.M.R. characterization, proves to be the desired product having formula (XVII) . Elemental analysis: Calculated C: 81.7 H: 8.1 N: 10.2 Found C: 81.2 H: 8.1 N: 9.7

EXAMPLE 9 : N- (methyl) -N-{ (E) -1- [6- (2 , 6-diisopropylphenyl- ethaneimidoyl) -2-pyridinyl] ethylidene}amine (XVIII) .

(XVIII)

0.64 g (2.0 mmoles) of intermediate A (formula (VII), obtained as described above) are suspended, in a 100 ml flask, in 20 ml of anhydrous ethanol. 3 ml of a 2M solution of methylamine in THF, 4 drops of formic acid and 20 ml of THF are added. The reaction mixture is left under stirring for 20 hours at room temperature, with the formation of a limpid solution. The solution is concentrated under vacuum until a microcrystalline solid precipitates, which, after elemental analysis and N.M.R. characterization, proves to be the desired product having formula (XVIII) . Elemental analysis: Calculated C: 78.8 H: 8.7 N: 12.5

Found C: 78.4 H: 8.7 N: 11.5

EXAMPLE 10: Synthesis of [N-benzyl-N- ( (E) -l-{6- [ (2, 6- diisopropylphenyl-ethaneimidoyl] -2-pyridinyl}-ethylidene) - amine] cobalt [II] dichloride (XIX) .

10 ml of distilled and deaerated n-butanol are brought to reflux temperature and 0.12 g of CoCl₂-6H₂0 are dissolved therein, under a stream of nitrogen. 0.20 g of the ligand

N- (benzyl) -N-{ (E) -1- [6- (2, 6-diisopropylphenyl-ethaneimid- oyl) -2-pyridinyl] ethylidene}amine (formula XVII), prepared according to example 8, are added to the resulting mixture. A solution is rapidly formed, from which a light green mi- crocrystalline solid precipitates, after about 2 hours, and which, after washing and characterization, proves to be the desired product having formula (XIX) (0.163 g, 0.30 mmoles) .

The structure formula of the complex thus obtained, as determined by X-rays, is indicated in figure 2. Elemental analysis: Calculated C: 62.2 H: 6.1 N: 7.7

Found . C: 61.6 H: 6.2 N: 7.6 EXAMPLE 11: Synthesis of [N-methyl-N- ( (E) -l-{6- [ (2, 6- diisopropylphenyl-ethaneimidoyl] -2-pyridinyl}-ethylidene) - amine] cobalt dichloride (XX) .

0.14 g of CoCl₂-6H₂0 are dissolved in 5 ml of distilled and deaerated n-butanol, under a stream of nitrogen. 0.20 g of the ligand N- (methyl) -N-{ (E) -1- [6- (2, 6-diisopropylphen- ylethaneimidoyl) -2-pyridinyl] ethylidene}amine (formula

XVIII) , prepared according to example 9, are added to the resulting mixture. A solution is rapidly formed, from which a yellow-green microcrystalline solid precipitates, after about 2 hours, and which after washing and characteriza- tion, proves to be the desired product having formula (XX)

(0.136 g, 0.29 mmoles).

The structure formula of the complex thus obtained, as determined by X-rays, is indicated in figure 1. Elemental analysis: Calculated C: 56.9 H: 6.3 N: 9.5 Found C: 57.0 H: 6.5 N: 8.7

EXAMPLE 12 : Synthesis of [N-{ (E) -1- [6- (cyclohexylethane- imidoyl) -2-pyridinyl] ethylidene}-2, 6-diisopropylaniline] cobalt dichloride (XXI) .

10 ml of distilled and deaerated n-butanol are brought to reflux temperature and 70 mg (0.294 mmoles) of CoCl₂-6H₂0 are dissolved therein, under a stream of nitrogen. The vol- ume of the solution is reduced to about 8 ml. 0.135 g

(0.334 mmoles) of N-{ (E) -1- [6- (cyclohexylethaneimidoyl) -2- pyridinyl] ethylidene}-2, 6-diisopropylaniline (formula X), prepared according to example 1, are added to the resulting mixture and, after 10 minutes, it is concentrated in a stream of nitrogen to a volume of about 5 ml, 7 ml of n- heptane are added and the mixture is left to cool slowly.

A crystalline precipitate is obtained in the form of green needles, which, after characterization, proves to be the desired product having formula (XXI) (0.155 g, 0.241 mmoles, yield 82%) having a molecular weight of 644.1.

Elemental analysis: Calculated C: 60.78 H: 6.99 N: 8.87

Found C: 60.55 H: 7.01 N: 8.72

I.R.: V(C=N_I) 1590 cm^"1; V(_C=N2) 1587 cm^"1

Reflectance spectrophotometry (5000-20000 cm^"1) : 5400 cm^"1; 8900 cm^"1; 10500 cm^"1; 15400 cm^"1; 16700 cm^"1(sh.); 17800 cm^" ( sh . ) .

EXAMPLE 13 : Synthesis of [N- (2 , 6-diisopropylphenyl) -N- [ (E)

1- (6 - { [ (IR) -1-phenylethyl] ethaneimidoyl} - 2 -pyridinyl) ethyl - idene] amino] iron [II] dichloride (XXII)

The same procedure is adopted as described in example 8 above, but using the following reagents and quantities, instead of the compound having formula (X) and CoCl₂-6H₂0 respectively.

Reagents mmoles grams

Compound having formula (XI) (Ex. 2) 0.33 0.146

FeCl₂-4H₂0 0.33 0.066

At the end, 0.159 g of a dark blue crystalline solid are obtained, which, after characterization, proves to be the desired product having formula (XXII) (0.284 mmoles, yield 86%) having a molecular weight of 560.7.

EXAMPLE 14 : Synthesis of [N- (2, 6-diisopropylphenyl) -N- [ (E) l-(6-{[(lS)-l- (2-naphthyl) ] ethaneimidoyl}-2-pyridinyl) ethylidene] amine] nickel [II] dibromide (XXIII) (XXIII )

The same procedure is adopted as described in example 8 above, but using the following reagents and quantities, instead of the compound having formula (X) and CoCl₂-6H₂0 respectively.

Reagents mmoles grams

Compound having formula (XII) (Ex. 3) 0.33 0.163

NiBr₂ 0.33 0.072

At the end, 0.220 g of a brown crystalline solid are obtained, which, after characterization, proves to be the desired product having formula (XXIII) (0.316 mmoles, yield 96%) having a molecular weight of 694.2.

I.R.: V(C=N) 1586 cm^"1

Reflectance spectrophotometry (5000-20000 cm^"1) : 9080 cm^"1; 10000 cm^"1; 12200 cm^"1; 15400 cm^"1; 18000 cm^"1.

Elemental analysis: Calculated C: 57.09 H: 5.37 N: 6.05

Found C: 57.00 H: 5.36 N: 5.97 EXAMPLE 15: Synthesis of [N- (2 , 6-diisopropylphenyl) -N- [ (E) -

1- (6-{ [ (IR) -1-phenylethyl] ethaneimidoyl}-2-pyridinyl) eth- ylidene] amine] nickel [II] dibromide (XXIV).

The same procedure is adopted as described in example 8 above, but using the following reagents and quantities, instead of the compound having formula (X) and CoCl₂-6H₂0 respectively.

Reagents mmoles grams

Compound having formula (XI) (Ex. 2) 0.33 0.146

NiBr₂ 0.33 0.072

At the end, 0.187 g of a brown solid are obtained, which, after characterization, proves to be the desired product having formula (XXIV) (0.290 mmoles, yield 88%) having a molecular weight of 644.1.

Elemental analysis: Calculated C: 54.07 H: 5.47 N: 6.52

Found C: 54.20 H: 5.45 N: 6.48

Reflectance spectrophotometry (5000-20000 cm^"1) : 8850 cm^"1;

10050 cm^"1 (sh.); 12500 cm^"1; 18000 cm^"1 (sh.).

EXAMPLE 16 : Synthesis of [N-{ (E) -1- [6- (cyclohexylethane- imidoyl) -2-pyridinyl] -ethylidene}-2, 6-diisopropylaniline] - iron [II] dichloride (XXV)

The same procedure is adopted as described in example 8 above, but using the following reagents and quantities,

instead of the compound having formula (X) and CoCl₂-6H₂0 respectively.

Products mmoles grams

Compound having formula (X) (Ex. 1) 0.33 0.146

FeCl₂-4H₂0 0.33 0.066

At the end, 0.110 g of a dark blue crystalline solid are obtained, which, after characterization, proves to be the desired product having formula (XXV) (0.232 mmoles, yield 81%) having a molecular weight of 530.4.

Elemental analysis: Calculated C: 61.15 H: 7.03 N: 7.92

Found C: 60.97 H: 6.91 N: 7.88

I.R.: V(_C=NI) 1580 cm^"1; V_(C=_N2) 1589 cm^"1

Reflectance spectrophotometry (5000-20000 cm^"1) : 8000 cm^"1;

14400 cm^"1; 18100 cm^"1(sh.).

EXAMPLE 17: Synthesis of [N-{ (E) -1- [6- (cyclohexylethane- imidoyl) -2-pyridinyl] ethylidene}-2 , 6-dimethylaniline] nickel [II] dibromide (XXVI)

The same procedure is adopted as described in example 8 above, but using the following reagents and quantities, instead of the compound having formula (X) and CoCl₂-6H₂0 respectively. Products mmoles grams

Compound having formula (XII) (Ex. 4) 0.288 0.100

NiBr₂ 0.288 0.063

At the end, 0.152 g of a brown crystalline solid are obtained, which, after characterization, proves to be the desired product having formula (XXVI) (0.270 mmoles, yield

94%) having a molecular weight of 566.0.

Elemental analysis: Calculated C: 48.01 H: 5.16 N: 7.42

Found C: 47.92 H: 5.28 N: 7.23

EXAMPLE 18 : Synthesis of [N-{ (E) -1- [6- (cyclohexylethane- imidoyl) -2-pyridinyl] ethylidene}-2, 6-dimethylaniline] iron- [II] dichloride (XXVII)

(XXVII)

The same procedure is adopted as described in example ₈ above, but using the following reagents and quantities, instead of the compound having formula (X) and CoCl₂-6H₂0 respectively. Products mmoles grams

Compound having formula (XII) (Ex. 4) 0.288 0.100

FeCl₂-4H₂0 0.288 0.057

At the end, 0.110 g of a dark blue crystalline solid are obtained, which, after characterization, proves to be the desired product having formula (XXVII) (0.232 mmoles, yield 81%) having a molecular weight of 474.2.

Reflectance spectrophotometry (5000-20000 cm^"1) : 8330 cm^"1

(only evident band)

Elemental analysis: Calculated C: 58.25 H: 6.16 N: 8.86 Found C: 58.13 H: 6.29 N: 8.68

EXAMPLE 19: Synthesis of [N-{ (E) -1- [6- (cyclohexylethaneimidoyl) -2-pyridinyl] ethylidene}-2, 6-dimethylaniline] cobalt [II] dichloride (XXVIII)

The same procedure is adopted as described in example 6 above, but using the following reagents and quantities, instead of the compound having formula (X) and CoCl₂-6H₂0 respectively.

Products mmoles grams

Compound having formula (XII) (Ex. 4) 0.288 0.100

CoCl₂-6H₂0 0.288 0.069

At the end, 0.116 g of a green crystalline solid are obtained, which, after characterization, proves to be the desired product having formula (XXVIII) (0.243 mmoles, yield 84%) having a molecular weight of 477.3. Elemental analysis: Calculated C: 57.87 H: 6.12 N: 8.80

Found C: 57.61 H: 6.25 N: 8.61 Reflectance spectrophotometry (5000-20000 cm^"1) : 5600 cm^"1; 8000 cm^"1; 10600 cm^"1; 15200 cm^"1; 16500 cm^"1; 18000 cm^"1 EXAMPLE 20 : Synthesis of the complex [N-diphenylmethyl-N- ( (E) -l-{6- [ (2, 6-diisopropylphenylethaneimidoyl] -2-pyridinyl}ethylidene) amine cobalt [II] dibromide (XXIX)

0.18 g of CoBr₂-6H₂0 are dissolved in 10 ml of n- butanol. 0.35 g of the tridentate chelating agent having formula (XIV) , obtained according to the process described in example 5 above, are added, at room temperature, to the solution thus obtained. On resting, a green solid precipitates, which is filtered and recrystallized from CH₂Cl₂/n- butanol. After characterization, the crystalline solid proves to be the desired compound having formula (XXIX) . Elemental analysis C% H% N%

57.80 5.27 5.94 theoretical 56.8 5.2 5.84 experimental EXAMPLE 21: Synthesis of the complex [N-l, 2-diphenylethyl- N- ( (E) -l-{6- [ (2, 6-diisopropylphenylethaneimidoyl] -2-pyrid- inyl}ethylidene) amine cobalt [II] dibromide (XXX)

0.18 g of CoBr₂-6H₂0 are dissolved in 10 ml of n- butanol . 0.3 g of the tridentate chelating agent having formula (XV) , obtained according to the process described in example 6 above, are added, at room temperature, to the solution thus obtained. On resting, a green solid precipitates, which is filtered and recrystallized from CH₂Cl₂/n- butanol, obtaining at the end 0.27 g of the desired complex having formula (XXX) . Elemental analysis C% H% N% 58.36 5.45 5.83 theoretical 57.1 5.41 5.71 experimental EXAMPLE 22: Synthesis of the complex [N-benzylyl-N- ( (E) -1-

{6- [ (2-tert-butylphenylethaneimidoyl] -2-pyridinyl}ethyli- dene) amine cobalt [II] dibromide (XXXI)

0.25 g of CoBr₂-6H₂0 are dissolved in 10 ml of n- butanol . 0.3 g of the tridentate chelating agent having formula (XVI) , obtained according to the process described in example 7 above, are added, at room temperature, to the solution thus obtained. On resting, 0.28 g of the desired complex having formula (XXXI) precipitate as a green solid which is filtered and recrystallized from CH₂Cl₂/n-butanol .

Elemental analysis C% H% N%

51.85 4.85 6.97 theoretical

51.2 4.4 6.72 experimental EXAMPLE 23: Polymerization of ethylene

0.025 mmoles of the complex having formula (XX) [N-

{ (E) -1- [6- (methyl) ethane-imidoyl) -2-pyridinyl] ethylidene}- 2, 6-diisopropylaniline] cobalt (II) dichloride, obtained according to the process described in example 11 above, dis- solved in 150 ml of anhydrous toluene, followed by 0.8 ml of MAO (1.57 M solution in toluene) (ratio Al/Co = 50), are charged (after effecting the vacuum- itrogen operation at least three times over a period of two hours and under static vacuum conditions) , into a 300 ml volume Buchi glass autoclave, equipped with a propeller stirrer, valve for the gas inlet, thermocouple jacket and valve for charging the solutions containing the components of the catalytic system. At this point the stirring is started and the autoclave is pressurized with ethylene at 0.7 MPa, the pressure being kept constant for the whole duration of the test. The temperature increases from the initial 25°C to 32.4°C after 30 minutes. At this stage, the autoclave is depressurized and the polymerization stopped by the addition of 20 ml of methanol . The polymer is recovered by precipitation in about 600 ml of methanol acidified with HCl, filtered and dried under vacuum at 50°C for about 8 hours.

At the end 6 g of polyethylene are obtained (activity 240 g_PE/mmole_Co) having the following characteristics measured by means of GPC: M_n=28800, M_w=51000, M_w/M_n=1.77. EXAMPLE 24: polymerization of ethylene

The same procedure is adopted, using the same reagents as in example 23 above, with the only difference that 0.025 mmoles of the complex [N-benzyl-N- ( (E) -l-{6- [ (2, 6-diisopro- pylphenylethaneimidoyl] -2-pyridinyl}ethylidene) amine iron chloride, and 0.8 ml of a solution of MAO (Al/Fe = 50), are charged. During the polymerization the temperature increases from the initial 20°C to 39°C after 30 minutes.

At the end 7 g of polyethylene are obtained (activity 280 gp_E/mmole_Fe) having the following characteristics meas- ured by means of GPC: M_n=6509, M_w=105,898, M_w/M_n=16.27. EXAMPLE 25: polymerization of ethylene

The same procedure is adopted as in example 23 above, with the only difference that 0.025 mmoles of the complex having formula (XXIX) [N-diphenylmethyl-N- ( (E) -l-{6- [(2,6- diisopropylphenylethaneimidoyl] -2-pyridinyl}ethylidene) amine cobalt [II] dibromide, obtained according to the previous example 20, and 0.8 ml of a solution of MAO (Al/Co = 50) , are charged. The temperature increases from the initial 27°C to 33°C after 30 minutes. At the end 7 g of polyethylene are obtained (activity 280 gp_E/mmole_Co) • EXAMPLE 26

The same procedure is adopted as in example 23 above, with the only difference that 0.025 mmoles of the complex having formula (XXII) [N- (2, 6-diisopropylphenyl) -N- [ (E) - 1-

(6-{ [ (IR) -1-phenylethyl] ethaneimidoyl}-2-pyridyl) ethylide- ne] amino] iron dichloride, obtained according to the previous example 13, and 0.8 ml of a solution of MAO (Al/Fe = 50) , are charged. During the polymerization, the tempera- ture increases from the initial 26°C to 37°C after 30 min- utes .

₅ g of polyethylene are obtained (activity ²²⁰ g_PE/mmoles_Fe) having the following characteristics measured by means of _GP_C: M_n=2672, M_w=32900, M_w/M_n=12.³.

Claims

₁. _An organic compound suitable as a neutral ligand of transition metals in an oxidation state different from zero, consisting of a di-imine of 2, 6-diacylpyridine (DIAP) , having the following general formula (IV) :

X \

R- R wherein:

R' and R' ' may independently be hydrogen or a hydrocarbon radical having from 1 to 10 carbon atoms, optionally halogenated,

S¹, S² and S³ each independently represent a substitu- ent of the pyridine ring selected in the group consisting of hydrogen, halogen and linear or branched alkyl or aryl groups, having from 1 to 15 carbon atoms, optionally functionalized or joined to each other to form one or more condensed cycles with the pyridine ring; each of the R¹ and R² groups is independently a C₁-C₁5 alkyl group or a C₆-C_ι8 aryl group, optionally substituted, on the condition that one of the R¹ or R² groups is alkyl and the other is aryl. ₂. The organic compound according to claim 1, wherein said R¹ or R² with the meaning of an aryl group is selected from groups having the following formula (VI) :

wherein the different R₃, R₄, R₅, R₆ and R₇ groups, abbreviated Ri (i = 3,...,7), are independently selected from hydrogen, halogen, or hydrocarbyl groups having from 1 to 15 carbon atoms. 3. The organic compound according to claim 2, wherein, in the aryl group having formula (VI) , the R₅ or R₆ groups are independently selected from methyl and cyclic or branched alkyl radicals having from 3 to 12 carbon atoms, and the R₃, R₄ and R₇ radicals are independently selected from methyl and hydrogen. 4. The organic compound according to any of the previous claims, wherein said R¹ or R² with the meaning of an alkyl group is selected from methyl, ethyl groups and cyclic or branched alkyl groups, optionally substituted with an aromatic or cycloaliphatic group having from 5 to 10 carbon atoms.

5. The organic compound according to any of the previous claims, wherein each R' or R¹ ' group in formula (IV) is an alkyl group having from 1 to 5 carbon atoms, preferably methyl, and the substituent groups of the pyridine ring S¹, S² and S³ are hydrogen.

6. A coordination metal complex having the following formula (V) :

(DIAP)M(X)_n (N) wherein: M is a metal selected from transition metals of groups 8 to 10 of the periodic table, in an oxidation state "s" which is positive and different from zero; each X is independently a group of an anionic nature bound to the metal as anion in an ionic couple or with a "σ" type covalent bond;

"n" expresses the number of X groups sufficient to neutralize the formal "+s" charge of the metal M, and is equal to "s" if all the X groups are monovalent; and (DIAP) represents a neutral organic ligand coordinated to the metal M; characterized in that said ligand (DIAP) consists of an organic compound according to any of the previous claims from 1 to 5. 7. The metal complex according to claim 6, wherein said oxidation state "s" of said metal M ranges from 1 to 3.

₈. The metal complex according to claim 6 or 7, wherein said metal M is selected from metals of groups 8 and 9 of the periodic table, preferably from Fe, Co, Ru, Rh and Ir in oxidation state "s" = +2.

9. The metal complex according to any of the previous claims, wherein said ligand (X) of an anionic nature is selected from halides, especially chloride and bro- mide, sulfates and acid sulfates, alkyl- and aryl- sulfonic groups, phosphates and polyphosphates, alkyl- and aryl-phosphonic groups, hydride, linear, cyclic or branched alkyl groups having from 1 to 15 carbon atoms, alkylsilyl groups having from 1 to 20 carbon at- oms, aryl groups having from 6 to 15 carbon atoms, alkoxyl or thioalkoxyl groups having from 1 to 10 carbon atoms, carboxylate or dicarboxylate groups having from 1 to 10 carbon atoms, a dialkylamide or alkylsi- lylamide group having from 2 to 15 carbon atoms . 10. A catalytic system for the (co) polymerization of α- olefins comprising at least the following two components, as such or combined with each other: (A) a complex of a metal M having formula (V) according to any of the previous claims from 6 to 9; (B) a co-catalyst consisting of at least one organic compound of an element M' different from carbon and selected from the elements of groups 2, 12, 13 or 14 of the periodic table.

1₁. The catalytic system according to claim 10, wherein said element M' in the co-catalyst (B) is selected from boron, aluminum, zinc, magnesium, gallium and tin, more particularly boron and aluminum.

12. The catalytic system according to claims 10 or 11, wherein said co-catalyst (B) is a linear or cyclic, polymeric aluminoxane.

13. The catalytic system according to the previous claim 12 , wherein the atomic ratio between the metal M in the complex having formula (V) which forms component (A) , and aluminum in the aluminoxane which forms the co-catalyst (B) , ranges from 100 to 5000.

14. The catalytic system according to the previous claims 10 or 11, wherein said co-catalyst (B) consists of at least one organometallic compound of boron, or a mixture thereof, capable of reacting with the complex having formula (V) by extracting from this a σ-bound ligand X as defined above, to form on the one hand at least one neutral compound, and on the other hand an ionic compound consisting of a cation containing the metal M coordinated to the ligand (DIAP) , and an or- ganic non-coordinating anion containing the metal M¹ , whose negative charge is delocalized on a multicentric structure.

₁₅. The catalytic system according to the previous claim 1₄, wherein the atomic ratio between the boron atom in component (B) and the atom M in the complex having formula (V) ranges from 0.5 to 10.

16. The catalytic system according to any of the previous claims 14 and 15, wherein said ligand X in the compound having formula (V) is different from alkyl, and said co-catalyst (B) comprises, in addition to said ionic compound of the metal M' , an alkylating agent consisting of an aluminum alkyl or an aluminum alkylhalide having from 1 to 8 carbon atoms in each alkyl residue. 17. A process for the (co) polymerization of α-olefins, either in continuous or batchwise, in one or more steps, at low (0.1-1.0 MPa), medium (1.0-10 MPa) or high (10- 150 MPa) pressure, at temperatures ranging from 20° to 250°C, optionally in the presence of an inert diluent, characterized in that at least one α-olefin is put under the above conditions in contact with a catalytic system according to any of the previous claims from 10 to 16. 18. The (co) polymerization process according to claim 17, carried out in the presence of an inert liquid con- sisting of an aliphatic or cycloaliphatic or aromatic hydrocarbon having from 3 to 8 carbon atoms, wherein said α-olefin comprises from 2 to 20 carbon atoms . and said metal M of the compound having formula (V) in said catalytic system, has a concentration ranging from 10^"8 to 10^"4 moles/liter.

19. The (co) polymerization process according to any of the previous claims 17 or 18, wherein said α-olefin is ethylene or a mixture of ethylene with a different polymerizable unsaturated monomer.