WO2000018776A1

WO2000018776A1 - Dimeric diimine transition metal complex and catalysts

Info

Publication number: WO2000018776A1
Application number: PCT/FI1999/000803
Authority: WO
Inventors: Timo Laine; Markku Leskelä
Original assignee: Borealis Technology Oy
Priority date: 1998-09-29
Filing date: 1999-09-29
Publication date: 2000-04-06
Also published as: FI982090A0; AU5986999A

Abstract

The invention relates to a dimeric late transition metal complex having the formula (1) wherein: Q, C and N form an unsaturated ring of aromatic nature; the divalent group Q is a chain of 3 or 4 atoms having the formula -[(CR)nZr]- wherein each R is independently selected from hydrogen, a halogen, a substituent comprising a heteroatom, and a C1-C30 hydrocarbyl, Z or each Z independently occurs at any place of the chain Q and is selected from -N=, -NR'-, R' being hydrogen or a C1-C10 hydro-carbyl, -S- and -O-, n is 2 or 3 and r is 0 or 1 when n+r is 3, and, n is 2, 3 or 4 and r is 0, 1 or 2 when n+r is 4; R10 is hydrogen, a halogen or a C1-C30 hydrocarbyl; R11 is hydrogen, a halogen or a C1-C30 hydrocarbyl; M is cobalt or nickel; X1 and X2 are independently selected from a monovalent ligand attached to M; A- is an anion and m is 0, 1 or 2, one of X¿1? and X2 optionally missing in the case m is 1 or 2, and the open lines from M and X1 are M-X1 and X1-M bonds, respectively, between the two mers of the dimer.

Description

DIMERIC DIIMINE TRANSITION METAL COMPLEX AND CATALYSTS

The invention relates to a dimeric late transition metal complex. The invention also relates to a late transition metal polymerization catalyst system comprising said complex, and the use of the catalyst system for the polymerization of ethylenically unsaturated compounds.

Only recently, see Johnson, L.K., Killian, CM., Brookhart, M., J. Am. Chem. Soc, 117(1995), 6414, high molecular weight polyethylene was prepared for the first time using late transition metal based catalyst systems. In the PCT-application WO 96/23010, the activation of nickel(II) and palladium(II) complexes bearing sterically demanding 1,4-diazabutadiene ligands by methyl aluminoxane or boron compounds and the polymerization of ethylene by means of the activated complexes were described.

In Rϋlke, R.E., Delis, J.G.P., Groot, A.M., Elsevier, C.J., van Leeuwen, P.W.N.M., Vrieze, K., Goubiz, K., Schenk, H., J. Organometallic Chem., 508(1996)109-120, the preparation of late transition metal complexes comprising different bidentate N-(2-pyridinylmethylene)hydrocarbylamino ligands was described. According to this document, the stability of the complexes were not good. Thus chloromethyl-[N- (2-pyridinylmethylene)-2-phenylethylamine]palladium was only stable for a few hours. As the activation of such complexes with e.g. aluminoxane destabilizes them still further, it was not expected that they could be used as stable polymerization catalyst components.

In the present invention, it was surprisingly found that certain dimeric late transition metal complexes were, contrary to the teaching of said document by Rϋlke et al., very stable. Additionally, they were activatable by e.g. uminoxane and catalytically active in the polymerization of ethylenically unsaturated compounds.

The dimeric late transition metal complexes according to the invention have the following general formula (1)

wherein: Q, C and N form an unsaturated ring of aromatic nature; the divalent group Q is a chain of 3 or 4 atoms having the formula -[(CR)_nZ_r]- wherein each R is independently selected from hydrogen, a halogen, a substituent comprising a heteroatom, and a Cι-C₃₀ hydrocarbyl, Z or each Z independently occurs at any place of the chain Q and is selected from -N= -NR'-, R' being hydrogen or a Cι-C₁₀ hydrocarbyl, -S- and -0-, n is 2 or 3 and r is 0 or 1 when n+r is 3, and, n is 2, 3 or 4 and r is 0, 1 or 2 when n+r is 4; R₁₀ is hydrogen, a halogen or a C C₃₀ hydrocarbyl; Rn is hydrogen, a halogen or a Cι-C₃₀ hydrocarbyl; M is cobalt or nickel; X_! and X₂ are independently selected from a monovalent ligand attached to M; A^~ is an anion and m is 0, 1 or 2, one of Xi and X₂ optionally missing in the case m is 1 or 2, and the open lines from M and Xi are M-Xi and X M bonds, respectively, between the two mers of the dimer.

Compared to earlier monomeric late transition metal complexes unexpected improvement and advantage has been achieved with a dimeric complex preferably having the formula (2)

wherein each of R1-R₄ is a substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group, R₁₀ is a group selected from hydrogen and a hydrocarbyl containing from 1 to 10 carbon atoms, Rπ is an aromatic group and M, Xi, X₂, A^" and m are the same as above.

Thus, it has been realized that dimeric late transition metal complexes comprising a bidentate N-(2-pyridinylmethylene)arylamino ligand are stable, activatable and active as catalysts in the polymerization of ethylenically unsaturated compounds.

In formula (2), the pyridine ring substituents Rr _t may be a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group. Typical organic groups are C C₁₀ alkyls, C₆-C₁₈ aryls, C₇-C₁ aralkyls and C₇-C₁₉ alkaryls. Typical ring constituents are those in which Ri and R₂ or R₂ and R₃ form together an aromatic ring which is fused with the pyridine ring to form isoquinoline. Further R₃ and R₄ may form together an aromatic ring which is fused with the pyridine ring to form quinoline. Larger fused ring systems like the three-ring phenantridine may also be used. Typical inorganic atoms or groups are e.g. nitro, halogen and acyl, provided that they are unreactive towards other moieties of the complex and non-coordinating. This criterion is also valid for the above ring substituents R _t.

Although the pyridine ring may have various non-reactive and non-coordinating substituents, Ri-R are preferably a hydrogen.

In formula (2), R₁₀ is a group selected from a hydrogen or a hydrocarbyl group containing from 1 to 10 carbon atoms. R₁₀ must also be internally unreactive and non-coordinating. Preferably, R₁₀ is a hydrogen.

In the preferred dimeric late transition metal complex according to the invention and expressed by formula (2), the group R_n may be any internally unreactive and non- coordinative aromatic substituent. By aromatic group is meant any group structure having a particularly stable series of occupied π-molecular orbitals. The aromatic group is typically described by the Hϋckel rule, according to which planar mono- cyclic completely conjugated hydrocarbons will be aromatic when the ring contains 4n+2 π-electrons, wherein n is the number of ring carbon atoms. Thus, all annulenes according to the Hϋckel rule are included. In addition, fused ring systems of aromatic type, as well as homoaromatic (partly aromatic) rings are also suitable.

Preferably, the aromatic group Ar has the formula (3)

wherein each of R₅-R₉ is a substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group. Naturally, these substituents are also internally unreactive and non-coordinating.

In formula (3), typical organic groups R₅-R₉ are C C₁₀ alkyls, C₆-C₁₈ aryls, C₇-C₁₉ aralkyls and C₇-C₁ alkaryls. Typical ring constituents Rs-R₉ form with the disclosed ring fused ring systems like naphthalene, anthracene, phenanthrene, etc., provided that they are non-coordinating and allow the coordination of the nitrogen atoms of the ligand to the late transition metal.

Preferably, Re-Rs are a hydrogen and R₅ and R₉ are independently selected from a Cι-C₂₀ alkyl, a C₆-C ₄ aryl, a C₇-C₃₀ alkaryl or a C₇-C₃₀ aralkyl. More preferably, R₅ and R are independently a branched C₃-C₁₀ alkyl, such as isopropyl or tert. butyl. Most preferably, R₅ and R are isopropyl.

The late transition metal M of the present complex is a transition metal selected from Groups 8-10 of the Periodic Table of the Elements (IUPAC 1990) which forms said dimeric complex, such as cobalt or nickel. According to the IUPAC recommendation of 1990, the Groups are numbered 1-18, whereby Group 8 is the so called Fe group, Group 9 is the so called Co group and Group 10 is the so called Ni group. M is preferably a transition metal selected from Groups 9 or 10 of said Periodic Table of the Elements, most preferably cobalt or nickel.

In addition to said bidentate ligand, the claimed late transition metal complex of formula (2) has one or two further ligands (or ions), X_} and X , bonded to the metal M. These ligands may be any monovalent (mono-dentate) ligand capable of forming a coordination bond with the metal M and being unreactive towards the other ligands of the complex. The ligands Xj and X may be part of a dimer bridge and, optionally, be a cationic or cation inducing species. Typically, halogens form bridges and electron donating compounds such as tetrahydrofurane THF form cations. In the case of cations, the other of Xi and X₂, preferably a halogen, may optionally be missing.

Preferably, the monovalent ligands Xi and X₂ are independently a hydrogen, a halogen, a C C₁₂ hydrocarbyl, a C C₁₂ hydrocarbyloxy, and, in the case m is 1 or 2, optionally an electron donor compound. Most preferably, Xi and X₂ are independently a halogen, preferably chlorine or bromine, or a C1-C₅ alkyl, preferably methyl. As halogens form the strongest bridges, the mers of the dimer preferably have at least one halogen as the ligand Xj or X₂.

Although the invention also relates to said complex in the form of an ion pair, A^" being e.g. the strong anion [B(C₆F₅)₄]^~, the complex is preferably neutral, that is, in formula (2), m is preferably 0.

Typically, the present late transition metal complex is selected from di-μ-chlorodi- cWorobis[2,6-bis(l-methylethyl)-N-(2-pyridmylmethylene)phenylamm

(II), di-μ-bromodibromobis[2,6-bis(l-methylethyl)-N-(2-pyridmylmethylene)- phenylanτine]dinickel(II), di-μ-bromodibromobis[2,6-dimethyl-N-(2-pyridinyl- methylene)phenylanύne]dinickel(II), di-μ-bromodibromobis { 2, 6-bis( 1 -methyl- ethyl)-N-[(6-methyl-2-pyridmyl)methylene]phenylamme}dinickel(II), di-μ-bromodibromobis {2, 6-bis( 1 -methylethyl)-N-[ 1 -(2-pyridinyl)ethylidene]phenylamine } di- nickel(II) and di-μ-bromodibromobis[2,6-bis(l-methylethyl)-N-(phenyl-2-pyridinyl- methylene)phenylamine]dinickel(II).

The invention also relates to a process for the preparation of the late transition metal complex described above. For example, in the process, an N-(2-pyridinyl- methylene)aιylamine of the formula (6)

wherein each of RpRi is a non-coordinating substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group, R₁₀ is a non-coordinating group selected from a hydrogen or an organic group containing from 1 to 10 carbon atoms, and Rπ is a non-coordinating aromatic group, is reacted with a compound of the formula (7)

DMX,X₂ (7a) or MXιX₂ (7b)

wherein D is an exchangeable bidentate ligand, M is a transition metal selected from one of Groups 8-10 of the Periodic Table of the Elements (IUPAC 1990), and X, and X are independently a monovalent ligand, the reaction product is recovered, and, optionally, in the case m is 1 or 2, said reaction product is further reacted with an ion exchanging compound comprising a cation and a non-coordinating anion A^~.

With respect to Ri- } in formula (6), they are as defined above in connection with formula (2), i.e. preferably a hydrogen. The same applies for R₁₀ and K , whereby in formula (6), Ar preferably has the formula (3)

wherein each of R₅-R₉ is a substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms or an inorganic atom or group.

Most preferably, said N-(2-pyridinyj^ethylene)arylamine of formula (6) has the specific formula (8)

wherein R₁₀ is the same as above, R₅ and R₉ are independently a CrC₂₀ alkyl, a C₆-C₂ aryl, a C₇-C₃₀ alkaryl or a C₇-C₃₀ aralkyl.

In accordance with the corresponding substituents of the claimed late transition metal complex, R₁₀ is preferably a hydrogen and R₅ and R₉ are preferably independently a branched C₃-C₁₀ alkyl, more preferably isopropyl or tert. butyl, most preferably isopropyl.

A typical N-(2-pyridinylmethylene)arylamine useful in the preparation of the described late transition metal complex is 2,6-bis(l-methylethyl)-N-(2-pyridinyl- methylene)phenylamine.

According to the claimed complex preparation process, the N-(2-pyridinyl- methylene)arylamine is reacted with a compound of the above formula (7a) having an exchangeable bidentate ligand, or, in the case of some late transition metals, directly with a compound of the above formula (7b) having only the two stationary ligands Xi and X₂ bound to the metal. The former is often the case with Ni and the latter is often the case e.g. with Co.

When using exchangeable bidentate ligands, they are preferably bidentate dienes or bidentate diethers, which are capable of coordinating with the late transition metal. Preferably, in formula (7a), the exchangeable bidentate ligand D is selected from 1,5-cyclooctadiene and 1,2-dimethoxyethane.

As the late transition metal of formula (7) will remain in the final complex, the same applies for it as is stated above in connection with the complex of the invention. Thus, M is preferably a transition metal selected from Groups 9 or 10 of the Periodic Table of the elements (IUPAC 1990), most preferably cobalt or nickel. The same applies for Xi and X₂, i.e. in formula (7), Xi and X₂ are preferably independently a hydrogen, a halogen, a C C₁ hydrocarbyl, a C C₁₂ hydrocarbyl- oxy, and, in the case m is 1 or 2, optionally an electron donor compound. Most preferably, Xi and X₂ are independently a halogen, preferably chlorine or bromine, or a C1-C₅ alkyl, preferably methyl.

The invention also relates to a late transition metal catalyst system for the polymer- ization of ethylenically unsaturated compounds. It comprises a dimeric late transition metal complex having the formula (1)

wherein: Q, C and N form an unsaturated ring of aromatic nature; the divalent group Q is a chain of 3 or 4 atoms having the formula -[(CR)_nZ_r]- wherein each R is independently selected from hydrogen, a halogen, a substituent comprising a heteroatom, and a -C₃o hydrocarbyl, Z or each Z independently occurs at any place of the chain Q and is selected from -N=, -NR'-, R' being hydrogen or a Ci-C₁₀ hydrocarbyl, -S- and -0-, n is 2 or 3 and r is 0 or 1 when n+r is 3, and, n is 2, 3 or 4 and r is 0, 1 or 2 when n+r is 4; R₁₀ is hydrogen, a halogen or a Cι-C₃o hydrocarbyl; Rn is hydrogen, a halogen or a Cι-C₃₀ hydrocarbyl; M is cobalt or nickel; Xi and X₂ are independently selected from a monovalent ligand attached to M; A^~ is an anion and m is 0, 1 or 2, one of Xi and X₂ optionally missing in the case m is 1 or 2, and the open lines from M and Xi are M-Xi and Xi-M bonds, respectively, between the two mers of the dimer.

The late transition metal catalyst system preferably comprises:

a) a dimeric late transition metal complex component having the formula (2)

wherein each of R1-R₄ is a substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group, R₁₀ is a group selected from hydrogen and a hydrocarbyl containing from 1 to 10 carbon atoms, R_n is an aromatic group and M, Xi, X₂, A^" and m are the same as above, and

b) a cocatalyst component selected from

(i) an aluminoxane having one of the following formulas (4)

(4 linear)

(4 _{cy ic})

(OAlR')_p <⁴ S^eneral)

wherein each R is the same or different and is a Ci-Cio alkyl group and p is an integer between 1 and 40, and

(ii) an organometallic compound having the formula (5)

(R"_qMX'_r-q)_s (5)

wherein R" is a Ci-Cio hydrocarbyl, X is a halogen, q is 1, 2 or 3, r is the valency of M, M is a metal selected from Groups 1 to 3 and 13 of the Periodic Table of the Elements (IUPAC 1990), and s is 1 or 2.

If said organometallic compound having the formula (5) is used, M is preferably Al.

With respect to the dimeric late transition metal component defined in paragraph a) above the definition is the same as for the dimeric late transition metal complex defined before. Thus, Ri- j are preferably a hydrogen. Preferably R_u has the formula (3)

wherein each of R₅-R₉ is a substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group. Rδ-Rg are preferably a hydrogen, R₅ and R₉ are preferably independently selected from a Cι-C ₀ alkyl, a C₆-C₂₄ aryl, a C₇-C₃₀ alkaryl or a C₇- C₃₀ aralkyl.

Most preferably R₁₀ is a hydrogen and R₅ and R₉ are independently a branched C₃- C₁₀ alkyl such as isopropyl or tert. butyl. M is preferably a transition metal selected from Groups 9 or 10 of the Periodic Table of the Elements (IUPAC 1990) which forms a dimer of the above type, such as cobalt or nickel. Xi and X are e.g. independently a hydrogen, a halogen, a Ci-C₁₂ hydrocarbyl, a C Cι₂ hydro- carbyloxy, and, in the case m is 1 or 2, optionally an electron donor compound. Preferably, Xi and X are independently a halogen, preferably chlorine or bromine, or a Ci-Cs alkyl, preferably methyl, m is usually 0.

Said late transition metal complex component is according to one embodiment of the invention selected from di-μ-cMorodichlorobis[2,6-bis(l-methylethyl)-N-(2- pyτidinylmethylene)phenylanιine]dinickel(π), di-μ-bromodibromobis[2,6-bis(l- methylethyl)-N-(2-pyridmylmethylene)phenylamme]d di-μ-bromodi- bromobis[2,6-dimethyl-N-(2-pyridmylmethylene)phenylanιme]dinickel(II), di-μ- bromodibromobis{2,6-bis(l-methylethyl)-N-[(6-methyl-2-pyridmyl)methyk phenylamine}dinickel(II), di-μ-bromodibromobis{2,6-bis(l-methylethyl)-N-[l-(2- pyridinyl)ethylidene]phenylamme}dinickel(II) and di-μ-bromodibromobis[2,6-bis- ( 1 -methylethyl)-N-(j3henyl-2-pyri

In its widest scope, the cocatalyst or activator is selected from aluminoxanes of formula (4) and the alkyl metal halides or alkyl metal compounds of formula (5). The alkyl metal halides or alkyl metal compounds such as trimethyl aluniii-ium, triethyl aluminium and triisobutyl aluminium are generally used when the system is supported e.g on an inorganic oxide such as silica, alumina, silica-alumina, MgCl₂, etc. Aluminoxanes are generally used in homogenous systems when the catalyst system is in solution. Preferably said cocatalyst component is a Cι-C₁₀ aluminoxane, most preferably methyl aluminoxane.

In order to give as good polymerization results as possible when polymerizing ethylenically unsaturated compounds, the molar ratio Al/M is preferably between 10 and 10000, most preferably between 500 and 5000.

Last but not least, the invention relates to process for the polymerization of ethylenically unsaturated compounds. In the claimed polymerization process, under polymerization conditions, at least one polymerizable ethylenically unsaturated compound is contacted with a catalyst system comprising a dimeric late tiansition metal complex having the formula (1)

wherein: Q, C and N form an unsaturated ring of aromatic nature; the divalent group Q is a chain of 3 or 4 atoms having the formula -[(CR)_nZ_r]- wherein each R is independently selected from hydrogen, a halogen, a substituent comprising a hetero- atom, and a CrC₃₀ hydrocarbyl, Z or each Z independently occurs at any place of the chain Q and is selected from -N=, -NR'-, R' being hydrogen or a Cι-Cι₀ hydrocarbyl, -S- and -0-, n is 2 or 3 and r is 0 or 1 when n+r is 3, and, n is 2, 3 or 4 and r is 0, 1 or 2 when n+r is 4; R₁₀ is hydrogen, a halogen or a Ci-C₃₀ hydrocarbyl; Rn is hydrogen, a halogen or a Ci-C₃₀ hydrocarbyl; M is cobalt or nickel; Xi and X₂ are independently selected from a monovalent ligand attached to M; A^" is an anion and m is 0, 1 or 2, one of Xi and X₂ optionally missing in the case m is 1 or 2, and the open lines from M and Xi are M-X_t and X M bonds, respectively, between the two mers of the dimer.

Preferably, the catalyst system comprises

a) a late transition metal complex component having the formula (2)

wherein each of R1-R₄ is a substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group, R₁₀ is a group selected from hydrogen and a hydrocarbyl containing from 1 to 10 carbon atoms, R_u is an aromatic group and M, Xi, X₂, A^" and m are the same as above, and

b) a cocatalyst component selected from

(i) an aluminoxane having one of the following formulas (4)

(4 linear)

(4 cyclic)

(OA1R1 (4 general)

wherein each R' is the same or different and is a Cι-Cι₀ alkyl group and p is an integer, between 1 and 40, and

(ii) an organometallic compound having the formula (5)

(R"_qMX'_r._q)_s (5) wherein R" is a C C₁₀ hydrocarbyl, X' is a halogen, q is 1, 2 or 3, r is the valency of M, M is a metal selected from Groups 1 to 3 and 13 of the Periodic Table of the Elements (IUPAC 1990), and s is 1 or 2.

For the catalyst system used in the claimed polymerization process, the same applies as for the description above concerning the catalyst system as a product. Thus, in formula (2), R₁-R₄ are preferably a hydrogen. Preferably Ar has the formula (3)

wherein each of R₅-R is a substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group. e-Rs are preferably a hydrogen, R₅ and R₉ are preferably independently selected from a Cι-C₂₀ alkyl, a C₆-C₂₄ aryl, a C₇-C₃₀ alkaryl or a C₇- C₃₀ aralkyl. Most preferably R₁₀ is a hydrogen (see formula (2)) and R₅ and R₉ are independently a branched C₃-C₁₀ alkyl such as isopropyl or tert. butyl.

In formula (1 and 2), M is preferably a transition metal selected from Groups 9 or 10 of the Periodic Table of the Elements (IUPAC 1990), such as cobalt or nickel. X, and X₂ are e.g. independently a hydrogen, a halogen, a C C₁₂ hydrocarbyl, a Ci-Cι₂ hydrocarbyloxy, and, in the case m is 1 or 2, optionally an electron donor compound. Preferably, Xi and X₂ are independently a halogen, preferably chlorine or bromine, or a C C₅ alkyl, preferably methyl, m is usually 0.

Said late transition metal complex component is in the polymerization process preferably selected from di-μ-cMorodicUorobis[2,6-bis(l-methylethyl)-N-(2- pyridinylmethylene)phenylamine]dinickel(II), di-μ-bromodibromobis[2,6-bis(l- methylethyl)-N-(2-pyridmylmethylene)phenylanτme]dinickel(II), di-μ-bromodi- bromobis[2,6-dimethyl-N-(2-pyridmyj^ethylene)phenylanτme]dm di-μ- bromodibromobis{2,6-bis(l-methylethyl)-N-[(6-methyl-2-pyridinyl)methylene]- phenylanτine}dinickel(II), di-μ-bromodibromobis{2,6-bis(l-methylethyl)-N-[l-(2- pyridmyl)ethylidene]phenylamine}dimckel(II) and di-μ-bromodibromobis[2,6-bis- ( 1 -methylethyl)-N-( henyl-2-pyridmylmethylene)phenylamine] dinickel(II) . In said polymerization process, said cocatalyst component is preferably a Ci- o aluminoxane, most preferably methyl urninoxane. The molar ratio Al/M is preferably between 10 and 10000, most preferably between 500 and 5000.

The claimed polymerization process is suitable for a number of ethylenically unsaturated compounds as monomers. It is e.g. suitable for the polymerization of olefins such as ethylene, propylene, 1-butene, 1-hexene, cyclopentene, cyclobutene and norbornene. It is also suitable e.g. for the copolymerization of ethylene/- propylene, ethylene/1-butene, ethylene/1-hexene, ethylene/l,3-butadiene, ethylene/-

4-methyl-l-pentene, ethylene/α-ω-diolefϊns such as α-ω-octadiene, propylene/- cyclopentene, ethylene/norbomene, ethylene/dimethanooctahydrohaphthalene and ethylene/propylene/ethylidene norbornene. Preferably, said polymerizable ethylenically unsaturated compound is selected from ethylene, an α-C₃-C₂₀-olefin and a conjugated polymerizable ethylenically unsaturated compound. Most preferably, the polymerizable ethylenically unsaturated compound is ethylene or a mixture thereof with an α-C₃-C₁₀-olefin.

Examples

Figure Captions

Fig. 1 Crystal structure of complex 1 showing labeling scheme.

Fig. 2 Crystal structure of complex 2 showing the labeling scheme. Displacement ellipsoids are drawn at the 40% probability level. Hydrogen atoms are omitted for clarity. Selected bond lengths (A) and angles (°): Ni-Nl 2.039(2), Ni-N8 2.095(2), Ni-Cll 2.3965(8), Ni-Clla 2.3366(8), M-C12 2.2729(9), C6-C7 1.463(4), C7-N8 1.278(3), N8-C9 1.440(3); N1-M1-N8 79.37(9), Nl-Ni-Cll 91.08(6), Nl-Ni-Clla 161.14(6), N1-M-C12 94.00(6), Cll-Ni-Clla 85.53(3), Ni-Cll-Nia 94.47(3).

Fig. 3 Crystal structure of complex 3 with the labeling scheme. Displacement ellipsoids are drawn at the 40% probability level. Hydrogen atoms are omitted for clarity.

Fig. 4 Molecular structure of compound 4 showing the two crystallographically independent molecules of the asymmetric unit.

Fig. 5 Crystal structure of complex 5.

Fig. 6 Molecular structure of compound 6. The solvent molecules are omitted for clarity. Examples 1 and 2

A. Preparation of the complexes

General

All complex preparations were performed under argon atmosphere using standard Schlenk techniques. Acetone was dried by storing under argon with CaS0 granules, other solvents by refluxing with a drying agent (P₂0₅ for dichloromethane and sodium/benzophenone for the non-halogenated solvents) and distillation under argon. DicMoro(l,2-dimethoxyethane)nickel(II), (DME)NiCl , and dibromo(l,2-di- methoxyethane)nickel(II), (DME)NiBr₂, were prepared according to the literature. 2-pyridinecarboxaldehyde (Merck, 98 %), and 2,6-di(l-methylethyl)phenylamine (Aldrich, 90 %) were used as received. -1H NMR: Varian Gemini 200 spectrometer (200 MHz); CDC1₃, or [D6]acetone as solvent, TMS as internal standard. Elemental analyses were carried out at the University of Ulm, Germany.

2,6-bis(l-methylethyl)-N-(2-pyridirιylmethylene)phenylamine (L^)

The ligand was synthesized by modifying the literature method reported for the analogous 2,6-dimethyl compound. Ethanol (100 ml), 2,6-di(l-methylethyl)phenyl- amine (15.76 g, 80.0 mmol), and 2-pyridinecarboxaldehyde (8.57 g, 80.0 mmol) were combined and refluxed for 20 min. The solvent was removed and the residue was vacuum distilled followed by chromatography on basic alumina with pentane/- ethyl acetate (3:1) as eluent. Recrystallization from pentane yielded pale yellow crystals, 14.36 g (67 %). -1H NMR (CDC1₃): δ = 1.17 (d, 12H, H_Me), 2.97 (m, 2H, CHMe₂), 7.16 (m, 3H, H_arom), 7.42 (m, 1H, H_pyridine>4), 7.86 (t, 1H, H_phenyl>4), 8.27 (d, 1H, H_pyridine,3), 8.31 (s, 1H, CH=N), 8.73 (d, 1H, H_pyridine,6). - C₁₈H₂₂N₂ (266.39): calcd. C 81.16, H 8.32, N 10.52; found C 81.01, H 8.37, N 10.39.

Di-μ-chlorodichlorobis[2,6-bis(l-methylethyl)-N-(2-pyridinylmethylene)phenyl- aminejdinickelfll) (1)

To a suspension of (DME)NiCl (1.86 g, 8.45 mmol) in 40 ml dichloromethane was added the yellow ligand solution (2.34 g, 8.77 mmol in 15 ml CH₂C1₂). After stirring the brown reaction mixture for 24 h at room temperature, the solvent was evaporated and the resulting solid material was washed with pentane (3 x 20 ml) and dried in vacuum yielding complex 2a as orange powder, 2.65 g (79 %). -

(791.97): calcd. C 54.60, H 5.60, N 7.07; found C 54.61, H 5.94, N 6.68. Di-μ-bromodibromobis[2,6-bis(l-methylethyl)-N-(2-pyridinylmethylene)phenyl- aminejdinickelfll) (2)

Analogously to the preparation of 2a, complex 2b was prepared from (DME)NiBr₂ (0.40 g, 1.30 mmol) and L (0.36 g, 4.89 mmol) in CH₂C1₂. The orange-red powder was collected by filtration, washed with pentane (3 x 10 ml) and vacuum dried; yield 0.44 g (70 %). - C₃₆H₄₄Br₄N₄Ni₂ (969.77): calcd. C 44.59, H 4.57, N 5.78; found C 44.10, H 4.59, N 5.68.

B. Analysis of the complexes

X-ray crystal structure determinations

The crystals were mounted to a glass fiber using the oil drop method. Crystal data obtained with the ω-2θ scan mode were collected on an automated four-circle Rigaku AFC-7S diffractometer using graphite monochromatized Mo Kα radiation (λ = 0.71073 A) at 193 K. Three standard reflections were monitored after every 200 intensity scans. The intensities were corrected for Lorentz and polarization effects. Data sets were compressed to reflection files with TEXSAN Single Crystal Structure Analysis Software. The structures were solved with SHELXTL PC 4.1 program package using direct methods while further refinement with full-matrix least-squares on F was carried out with SHELXL 93. All nonhydrogen atoms were refined anisotropically. Hydrogen atoms were introduced to calculated positions (riding model) with 1.2 times the displacement factors of the host carbon atoms.

Fig. 1 shows compound 1 and Fig. 2 shows compound 2.

Table 1

Crystallographic data for complex 2

C. Polymerization of complexes 1 and 2

The polymerization conditions and results with catalysts 1 and 2/MAO are summarized in Table 2. Treatment of mckel complexes 1 and 2 with MAO produces active catalysts for the polymerization of alkenes. In the nickel catalyzed reactions both the activities and product molecular weights are dependent on the polymerization temperature. As polymerization at 20 °C provides low-melting or waxy polymers with activity comparable to other new systems lowering the temperature to 0 °C leads to an increase in molecular weights by an order of magnitude at the expense of declining catalytic activity. No significant difference in polymer properties was observed between the dichloro and dibromonickel(II) based systems (1/MAO and 2/MAO, respectively), which indicates a similar activation mechanism for both catalysts.

Even though numerous catalyst systems have been developed to date, fme-tuning of the catalyst precursor, and the ligand environment of the precursor in particular, is still one of the major tools to tailor polymer properties.

Table 2

Ethylene polymerization with catalysts 1 and 2/MAO^a

Polymerization conditions: T_p = 15 min (except at 0 °C 30 min), [A1]:[M] = 2000, polymerization medium = toluene. ^bActivity in kg polymer (mol catalyst x h)^"1.

Examples 3-6

A. General

All complex preparations were performed under an argon atmosphere using standard Schlenk techniques. Acetone was dried by storing under argon with CaS0₄ granules, other solvents by refluxing with a drying agent (CaH₂ for dichloromethane and sodium benzophenone for the nonhalogenated solvents) and distillation under argon. Commercial reagents, namely l-(2-pyridinyl)ethanone (Merck, 98%), phenyl-2-pyridinylmethanone (Merck, 98%), and 2,6-<h(l-methylethyl)phenylamine (Aldrich, 90%), were used as received. Dibromo(l,2-dimethoxyethane)nickel(II) [(DME)NiBr₂] [29], 2,6-dimethyl-N-(2-pyridmylmethylene)phenylaπ-ine (L₂) [21] and 2,6-bis(l-methylethyl)-N-[(6-methyl-2-pyridmyl)methylene]phenylanτ^ (L₃) [22] were prepared as reported earlier. Synthesis products were characterized, when applicable, using a Varian Gemini 200 spectrometer (200 MHz) with CDC1₃ as solvent and TMS as internal standard. Elemental analyses were carried out at the University of Ulm, Germany.

Polymerization procedure and equipment have been described in detail above. For polymer molecular weights and molecular weight distributions a Waters 150-C GPC chromatograph was used operating at 135 °C with 1,2,4-trichlorobenzene solvent and polystyrene calibration standards. Melting temperatures of preheated and cooled samples were determined by differential scarining calorimetry using a Perkin Elmer DSC-2 calorimeter. Analysis of polymer microstructure was based on NMR spectra recorded on a Varian XL-300 spectrometer at 125 °C. Samples were dissolved in l,l,2,2-tetrachloroethane-ci2 and a 10:1 weight ratio mixture of 1,2,4-trichlorobenzene and benzene-.io^' for 1H and ¹³C NMR measurements, respectively.

B. Ligand and complex preparation

2, 6-bis(l-methylethyl)-N-[l-(2-pyridinyl)ethylidene]phenylamine (L )

The ketone l-(2-pyridinyl)ethanone (1.82 g, 15.0 mmol) was combined with 2,6-di- (l-methylethyl)phenylamine (3.57 g, 18.1 mmol) and three drops of concentrated sulfuric acid as well as some sodium sulfate was added. This mixture was heated to 120 °C and stirring was continued at this temperature for 24 h. The dark brown, oily raw product was dissolved in 50 ml of dichloromethane, filtered, washed with 50 ml of water and dried with Na₂S0₄. After filtration and solvent evaporation the yellow- brown residue was purified by crystallization from ethanol affording yellow, cubic crystals; yield 1.41 g (34%). Cι₉H₂₄N₂ (280.41) Anal, calc: C 81.38; H 8.63; N 9.99%. Found: C 81.36; H 8.65; N 10.21%. 1H NMR (CDC1₃): δ 1.15 (d, 12H, H_Me), 2.21 (s, 3H, H_bridge._Me), 2.75 (m, 2H, CHMe₂), 7.11-7.20 (m, 3H, H_phenyl), 7.39 (m, 1H, H_pyri_di_ne,5), 7.82 (t, 1H, H_pyridinej4), 8.36 (d, 1H, H_{pyridme 3}), 8.69 (d, 1H,

H_pyridine,6) PPHl-

2, 6-bis(l-methylethyl)-N-(phenyl-2-pyridinylmethylene)phenylamine (L₅)

Analogously to the preparation of L₄, compound L₅ was synthesized from phenyl-2- pyridinylmethanone (2.75 g, 15.0 mmol) and 2,6-di(l-methylethyl)phenylamine (3.29 g, 16.7 mmol) at 120 °C. The ligand was obtained from ethanol as bright yellow microcrystalline powder, 1.68 g (33%). C₂₄H₂₆N₂ (342.48) Anal, calc: C 84.17; H 7.65; N 8.18%. Found: C 84.04; H 7.72; N 8.37%. 1H NMR (CDC1₃): δ 0.90 (d, 3H, H_Me), 0.97 (d, 3H, H_Me), 1.14 (d, 6H, H_Me), 2.93 (m, 2H, CHMe₂), 6.98-7.23 (m, 6H, H_arom), 7.45 (m, H_arom), 7.83 (m, H_arom), 8.25 (d, H_arom), 8.64 (m,

Harom) ppHl.

Di-μ-bromodibromobis[2,6-dimethyl-N-(2-pyridinylmethylene)phenylamine]- dinickelfll) (3)

To a suspension of [(DME)NiBr₂] (2.03 g, 6.6 mmol) in 20 ml of CH₂C1₂ was added the solution of ligand L₂ (1.42 g, 6.8 mmol) in 20 ml of CH₂C1 . The orange-red reaction mixture was stirred for 24 h at room temperature, after which the precipitate was collected by filtration, washed with pentane (2x10 ml), and vacuum- dried yielding complex 3 as orange-yellow powder, 1.55 g (55%). C ₈H₂₈Br₄N₄Ni₂ (857.55) Anal, calc: C 39.22; H 3.29; N 6.53%. Found C 38.97; H 3.60; N 6.39%.

Compounds 4-6 were prepared analogously from [(DME)NiBr₂] and the corresponding ligand in dichloromethane.

Di-μ-bromodibromobis{2,6-bis(l-methylethyl)-N-[(6-methyl-2-pyήdinyl)- methylene]phenylamine}dinickel(II) (4)

Orange-yellow powder, yield 57%. C₃₈H₂₈Br₄N₄Ni₂ (997.82) Anal, calc: C 45.74; H 4.85; N 5.61%. Found: C 45.56; H 4.81; N 5.53%.

Di-μ-bromodibromobis{2,6-bis(l-methylethyl)-N-[l-(2-pyridinyl)ethylidene]phenyl- amine}dinickel(II) (5)

Bright orange powder, yield 62%. C₃₈H₂₈Br₄N₄Ni₂ (997.82) Anal, calc: C 45.74; H 4.85; N 5.61%. Found: C 45.44; H 4.84; N 5.69%.

Di-μ-bromodibromobis[2,6-bis(l-methylethyl)-N-(phenyl-2-pyridinylmethylene)- phenylamine]dinickel(II) (6)

Orange-brown powder, yield 77%. C₄8H₅₂Br₄N₄Ni₂ • CH₂C1₂ (1206.89) Anal, calc: C 48.76; H 4.51; N 4.64%. Found: C 48.44; H 5.05; N 4.55%.

C. X-ray crystallography

The crystals were mounted to a glass fiber using the oil drop method [30]. Crystal data obtained with the ω2θ scan mode were collected on an automated four-circle Rigaku AFC-7S diffractometer using graphite-monochromatized Mo-K_α radiation (λ = 0.71073 A) at 193 K (except for complex 7 at 213 K). Three standard reflections were monitored after every 200 intensity scans. The intensities were corrected for Lorentz and polarization effects. For all compounds ψ-scans were used for absorption correction [31]. Data sets were compressed to reflection files with TEXSAN Single Crystal Structure Analysis Software [32]. Structure solution using direct methods and further refinement with full-matrix least-squares on F² was carried out with SHELX97 [33]. All nonhydrogen atoms were refined anisotropically. Hydrogen atoms were introduced to calculated positions (riding model) with 1.2 times the displacement factors of the host carbon atoms. Crystallographic data for the structural analysis have been deposited with the Cambridge Crystallographic Data Centre, CCDC No. 133658 (for 3), 133659 (for 4), 133660 (for 5) and 133661 (for 6). Copies of this information can be obtained free of charge from: CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: +44-1223-336 033; E-mail: deposit@ccdc.cam.ac.uk.

Table 3 Ethylene polymerization with catalysts 3-6/MAO.⁸

t t

^a [A1]:[M] = 2000, T_p = 30 min (except at 0 °C 60 min). ^b Polymerization temperature. ^c Molar amount of the catalyst precursor (in μmol Ni). ^d Ethylene pressure. ^e Activity in kg PE (mol catalyst x h)^"1. ^f Peak melting temperature. ^g Determined by 1H NMR spectroscopy. Broad melting peak.

Table 4 Crystallographic data for complexes 3-6

t

Table 4 Cont.

•4

^a S = [Σ[w(F₀ 2 - ϋ F_c 2N )2T ] / / ( <^■n-p) v]i¹/.² where n = data and p = parameters. ^b R = Σ I I F₀| - 1 F_c| I / Σ I F₀ 1 with F > 4Σ(F); function minimized is wR = [Σ[w(F₀ ² - F_c ²)²] / Σ[w(F

^c Minimum residual electron density - 1.127 e/A³; hole coordinates x = 0.4818, y = 0.9406, z = 0.1179; distance to nearest atom (Brl) 0.92 A.

Table 5 Selected bond lengths (A) and angles (°) for 3, 4, 5 and 6

t

Scheme 1

L₂: R = Me;R' = R"=H 3: R = Me;R = R"=H

L₃: R = tPr; R = H; R" = Me 4: R = tPr; R' = H; R" = Me

L₄: R=tPr;R' = Me;R'^* = H 5: R=/Pr;R' = Me;R"=H

L₅: R = tPr; R = Ph; R" = H 6: R = tPr; R' = Ph; R" = H

Claims

1. A dimeric late transition metal complex having the formula (1)

wherein: Q, C and N form an unsaturated ring of aromatic nature; the divalent group Q is a chain of 3 or 4 atoms having the formula ~[(CR)_nZ_r]- wherein each R is independently selected from hydrogen, a halogen, a substituent comprising a heteroatom, and a Cι-C₃o hydrocarbyl, Z or each Z independently occurs at any place of the chain Q and is selected from -N=, -NR'-, R' being hydrogen or a CrC₁₀ hydrocarbyl, -S- and -0-, n is 2 or 3 and r is 0 or 1 when n+r is 3, and, n is 2, 3 or 4 and r is 0, 1 or 2 when n+r is 4; R₁₀ is hydrogen, a halogen or a C_rC₃o hydrocarbyl; Rn is hydrogen, a halogen or a Cι-C₃₀ hydrocarbyl; M is cobalt or nickel; Xi and X₂ are independently selected from a monovalent ligand attached to M; A^~ is an anion and m is 0, 1 or 2, one of Xi and X optionally missing in the case m is 1 or 2, and the open lines from M and Xi are M-Xi and X M bonds, respectively, between the two ers of the dimer.

2. A dimeric late transition metal complex according to claim 1, characterized in that it comprises a bidentate N-(2-pyridmylmethylene)aιylamino ligand, and has the formula (2)

wherein each of R i is a substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group, R₁₀ is a group selected from hydrogen and a hydrocarbyl containing from 1 to 10 carbon atoms, R_n is an aromatic group and M, Xi, X₂, A^" and m are the same as above.

3. A late transition metal complex according to claim 2, characterized in that Ri- R_t are a hydrogen.

4. A late transition metal complex according to claim 2 or 3, characterized in that Rn has the formula (3)

wherein each of R₅-R₉ is a substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group.

5. A late transition metal complex according to claim 4, characterized in that Re-R₈ are a hydrogen and R5 and R₉ are independently selected from a Cι-C ₀ alkyl, a C₆-C₂₄ aryl, a C₇-C₃₀ alkaryl or a C₇-C₃₀ aralkyl.

6. A late transition metal complex according to claim 5, characterized in that R₁₀ is a hydrogen and R₅ and R₉ are independently a branched C₃-C₁₀ alkyl, preferably isopropyl or tert. butyl.

7. A late transition metal complex according to claim 6, characterized in that R₅ and R₉ are isopropyl.

8. A late transition metal complex according to one of claims 1 to 7, characterized in that Xi and X₂ are independently a hydrogen, a halogen, a CrC₁₂ hydrocarbyl, a C1-C12 hydrocarbyloxy, and, in the case m is 1 or 2, optionally an electron donor compound.

9. A late transition metal complex according to claim 8, characterized in that Xi and X₂ are independently a halogen, preferably chlorine or bromine.

10. A late transition metal complex according to any of claims 1 to 9, characterized in that m is 0.

11. A late transition metal complex according to any of claims 1 to 10, charac- terized in that it is selected from di-μ-chlorodichlorobis[2,6-bis(l-methylethyl)-N-

(2-pyridmy]methylene)phenylan-me]dinickel(II) and di-μ-bromodibromobis[2,6-bis- (l-methylethyl)-N-(2-pyridmylmethylene)phenylamme]dinickel(II).

12. A late transition metal catalyst system for the polymerization of ethylenically unsaturated compounds, characterized in that it comprises a dimeric late transition metal complex having the formula (1)

wherein: Q, C and N form an unsaturated ring of aromatic nature; the divalent group Q is a chain of 3 or 4 atoms having the formula -[(CR)_nZ_r]- wherein each R is independently selected from hydrogen, a halogen, a substituent comprising a heteroatom, and a Cι-C₃₀ hydrocarbyl, Z or each Z independently occurs at any place of the chain Q and is selected from -N=, -NR'-, R' being hydrogen or a Ci-C₁₀ hydrocarbyl, -S- and -0-, n is 2 or 3 and r is 0 or 1 when n+r is 3, and, n is 2, 3 or 4 and r is 0, 1 or 2 when n+r is 4; R₁₀ is hydrogen, a halogen or a Cι-C₃₀ hydrocarbyl; R_u is hydrogen, a halogen or a C C₃₀ hydrocarbyl; M is cobalt or nickel; Xi and X₂ are independently selected from a monovalent ligand attached to M; A^" is an anion and m is 0, 1 or 2, one of Xi and X₂ optionally missing in the case m is 1 or 2, and the open lines from M and Xi are M-Xi and Xi-M bonds, respectively, between the two mers of the dimer.

13. A late transition metal catalyst system according to claim 12, characterized in that it comprises

a) a dimeric late transition metal complex component having the formula (2)

wherein each of R₁-R₄ is a substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group, R₁₀ is a group selected from hydrogen and a hydrocarbyl containing from 1 to 10 carbon atoms, Rn is an aromatic group and M, X_l5 X₂ A^" and m are the same as above, and

b) a cocatalyst component selected from

(i) an aluminoxane having one of the following formulas (4) (4 linear)

R R R¹ r \ Al-(-0-A I l- θ-Al / (4 _cyclic)

(OAlR)_p (⁴ g^eneral)

wherein each R is the same or different and is a Ci-C₁₀ alkyl group and p is an integer between 1 and 40, and

(ii) an organometallic compound having the formula (5)

(R"_qMX'_r-q)_s (5)

wherein R" is a Ci-C₁₀ hydrocarbyl, X is a halogen, q is 1, 2 or 3, r is the valency of M, M is a metal selected from Groups 1 to 3 and 13 of the Periodic Table of the Elements (IUPAC 1990), and s is 1 or 2.

14. A catalyst system according to claim 13, characterized in that R1-R₄ are a hydrogen.

15. A catalyst system according to claim 13 or 14, characterized in that in formula (2), said R_π has the formula (3)

16. A catalyst system according to claim 15, characterized in that Rβ-Rs are a hydrogen, R₅ and R₉ are independently selected from a C C₂o alkyl, a C₆-C₂ aryl, a C₇-C₃₀ alkaryl or a C₇-C₃₀ aralkyl.

17. A catalyst system according to claim 16, characterized in that R₁₀ is a hydrogen and R5 and R are independently a branched C₃-C₁₀ alkyl, preferably isopropyl or tert. butyl.

18. A catalyst system according to claim 17, characterized in that R₅ and R₉ are isopropyl.

19. A catalyst system according to one of claims 12 to 18, characterized in that Xi and X₂ are independently a hydrogen, a halogen, a C C₁ hydrocarbyl, a Ci-C₁₂ hydrocarbyloxy, and, in the case m is 1 or 2, optionally an electron donor compound.

20. A catalyst system according to claim 19, characterized in that Xi and X₂ are independently a halogen, preferably chlorine or bromine.

21. A catalyst system according to any of claims 12 to 20, characterized in that m is O.

22. A catalyst system according to claim 21, characterized in that said dimeric late transition metal complex component is selected from di-μ-chlorodichlorobis- [2,6-bis(l-methylethyl)-N-(2-pyridmylmethylene)phenylamme]dim and di- μ-bromodibromobis[2,6-bis(l-methylethyl)-N-(2-pyridmylmethylene)phenylanιm dinickel(II).

23. A catalyst system according to any of claims 12 to 22, characterized in that said cocatalyst component is a Ci-C₁₀ aluminoxane, preferably methyl aluminoxane.

24. A catalyst system according to any of claims 13-23, characterized in that the molar ratio Al/M is between 10 and 10000, preferably between 500 and 5000.

25. A process for the polymerization of ethylenically unsaturated compounds, characterized in that at least one ethylenically unsaturated compound is under polymerization conditions contacted with a catalyst system comprising a dimeric late transition metal complex having the formula (1)

wherein: Q, C and N form an unsaturated ring of aromatic nature; the divalent group Q is a chain of 3 or 4 atoms having the formula -[(CR)_nZ_r]- wherein each R is independently selected from hydrogen, a halogen, a substituent comprising a heteroatom, and a Cι-C₃₀ hydrocarbyl, Z or each Z independently occurs at any place of the chain Q and is selected from -N= -NR'-, R' being hydrogen or a Ci-C₁₀ hydrocarbyl, -S- and -0-, n is 2 or 3 and r is 0 or 1 when n+r is 3, and, n is 2, 3 or 4 and r is 0, 1 or 2 when n+r is 4; R₁₀ is hydrogen, a halogen or a C C₃₀ hydrocarbyl; Rn is hydrogen, a halogen or a C C₃₀ hydrocarbyl; M is cobalt or nickel; Xi and X₂ are independently selected from a monovalent ligand attached to M; A^~ is an anion and m is 0, 1 or 2, one of Xi and X₂ optionally missing in the case m is 1 or 2, and the open lines from M and Xi are M-Xi and X M bonds, respectively, between the two mers of the dimer.

26. Process according to claim 25, characterized in that, under polymerization conditions, at least one polymerizable ethylenically unsaturated compound is contacted with a catalyst system comprising

a) a dimeric late transition metal complex component having the formula (2)

wherein each of R₁-R4 is a substituent independently selected from a hydrogen, an organic group or ring constituent containing from 1 to 20 carbon atoms, or an inorganic atom or group, R₁₀ is a group selected from hydrogen and a hydrocarbyl containing from 1 to 10 carbon atoms, Rn is an aromatic group and M, Xi, X₂, A^" and m are the same as above, and

b) a cocatalyst component selected from

(i) an aluminoxane having one of the following formulas (4)

R

\ I .R'

Al-(-0-Al- θ-Al (4 linear)

/

R \ R'

R R' R

\ I

|-Al-(-0-Al- O-Al-| (4 cyclic)

(OAlR'l (4 general)

wherein each R' is the same or different and is a Ci-C₁₀ alkyl group and p is an integer, between 1 and 40, and

(ii) an organometallic compound having the formula (5)

(R"_qMX_r-q)_s (5) wherein R" is a Ci-Cio hydrocarbyl, X' is a halogen, q is 1, 2 or 3, r is the valency of M, M is a metal selected from Groups 1 to 3 and 13 of the Periodic Table of the Elements (IUPAC 1990), and s is 1 or 2.

27. A polymerization process according to claim 26, characterized in that in formula (6), R₁-R₄ are a hydrogen.

28. A polymerization process according to claim 26 or 27, characterized in that in formula (2), said R_π has the formula (3)

29. A polymerization process according to claim 28, characterized in that R_<5-R₈ are a hydrogen and R5 and R₉ are independently a Cι-C₂o alkyl, a C₆-C₂ aryl, a C₇-C₃₀ alkaryl or a C₇-C₃₀ aralkyl.

30. A polymerization process according to claim 29, characterized in that R₁₀ is a hydrogen and R₅ and R₉ are independently a branched C₃-C₁₀ alkyl, preferably isopropyl or tert. butyl.

31. A polymerization process according to claim 30, characterized in that R₅ and R₉ are isopropyl.

32. A catalyst system according to one of claims 26 to 31, characterized in that in formula (6), Xi and X₂ are independently a hydrogen, a halogen, a Cι-C₁₂ hydrocarbyl, a Ci-C₁₂ hydrocarbyloxy, and, in the case m is 1 or 2, optionally an electron donor compound.

33. A catalyst system according to claim 32, characterized in that Xi and X₂ are independently a halogen, preferably chlorine or bromine.

34. A catalyst system according to any of claims 26 to 33, characterized in that in formula (2), m is 0.

35. A polymerization process according to claim 34, characterized in that said late transition metal complex component is selected from di-μ-chlorodichlorobis- [2,6-bis(l-methylethyl)-N-(2-pyridmylmethylene)phenylamme]d and di- μ-bromombromobis[2, 6-bis( 1 -methylethy dinickel(II).

36. A polymerization process according to any of claims 26 to 35, characterized in that said cocatalyst component is a Ci-C₁₀ aluminoxane, preferably methyl aluminoxane.

37. A polymerization process according to claim 36, characterized in that in said polymerization catalyst system, the molar ratio Al/M is between 10 and 10 000, preferably between 500 and 5000.

38. A polymerization process according to any of claims 25 to 37, characterized in that said ethylenically unsaturated compound is selected from ethylene, an α-C₃-C₂₀ olefin, a conjugated C -C₁₂ diene and an α-ω-C₅-Cι diolefin and polymerizable combinations thereof.