WO2015003815A1 - Immobilized metathesis tungsten catalysts and use thereof in olefin metathesis - Google Patents

Abstract

Compound of formula (I) wherein M is W; R¹ is H, aryl, heteroaryl, alkyl, or heteroalkyl, optionally substituted, respectively; R² and R³ can be the same or different and are alkyl, alkenyl, heteroalkyl, heteroalkenyl, aryl, or heteroaryl, optionally substituted, respectively, or hydrogen; R⁵ is a residue R⁶-X-, wherein R⁶ is alkyl, aryl, heteroalkyl, heteroaryl, optionally substituted, respectively; (R⁷, R⁸, R⁹)Si; wherein R⁷, R⁸, R⁹ are independently alkyl, alkoxy, phenyl or phenoxy, optionally substituted, respectively; (R¹⁰, R¹¹, R¹²)C, wherein R¹⁰, R¹¹, R¹² are independently phenyl, alkyl, optionally substituted, respectively; X = O, S, or NR¹³, wherein R¹³ is H; or alkyl or aryl, optionally substituted, respectively; or R⁵ is R⁶-CO-NR¹³, wherein R⁶ and NR¹³ have the meaning as defined above, or wherein R⁶ and R¹³ taken together form a carbon chain having from 2 to 6 carbon atoms; R⁵ is a 4 to 8 membered N-containing carbon ring, wherein N is linked to M; and R⁴ is a residue O-Si(O-)₃, and represents silica to which M is linked forming a M-O-Si(O-)₃ moiety, preferably wherein silica is comprised in a solid support; under the proviso that a compound in which R¹ = 2,6-diisopropylphenyl, R⁵ dimethylpyrrol-1-yl, R² = tBu, and R³ = H is excluded.

Description

IMMOBILIZED METATHESIS TUNGSTEN CATALYSTS AND USE THEREOF IN

OLEFIN METATHESIS

Description

The invention relates to immobilized organometallic tungsten catalysts. The catalysts are useful in the heterogeneous catalysis of olefin metathesis.

Due to the growing importance of olefin metathesis a great need exists for providing suit- able catalysts which beneficially perform at industrial scale. A considerable number of organometallic tungsten catalysts is known to homogeneously catalyze olefin metathesis. Although it is further known that in general heterogeneous catalysts may be easier separated off from reaction mixtures than homogeneous catalysts, e.g. by filtration, which is an advantage particular at industrial scale, few attention has been paid until now to re- spective heterogeneous tungsten catalysts which might be useful for olefin metathesis.

Rhers et al., Organometallics, 2006, vol. 25, 3554, disclose the formation of ethene and butenes, including 1-butene, from propene in a self-metathesis reaction by a silica supported tungsten catalyst. The catalyst has been characterized as syn-[(- SiO)(W(=NAr)(=CHtBu)(CH₂tBu)] (Ar = 2,6-iPrC₆H₃) of following formula:

F. Blanc et al., Proc. Natl. Acad. Sci. USA, August 26, 2008, vol. 105, no 34, 12123- 12127, later disclose the selective formation of ethene and 2-butene from propene in a self-metathesis reaction by a silica supported tungsten catalyst. This reaction is a heter- ogeneously catalyzed. The catalyst is of the following structure:

R = Me and is prepared by grafting [W(=N(2,6-diisopropylphenyl)(=CHCMe₃)(2_>5-Me₂C4l-l2N)₂] on

The efficacy of this catalyst expressed in terms of turnover frequency (TOF) needs to be improved for an economical use at an industrial scale. Thus, one object of the invention in view of this prior art is the provision of improved tungsten catalysts which may be used for the heterogeneous catalysis of olefin metathesis, and whose efficacy may be purposively adapted to the various types of olefin metathesis. Preferably, the turnover frequency (TOF) should be higher than the respective TOF which is achieved with the known structure.

This object is achieved with a silica based tungsten compound in which the substituents attached to W are selected such that the efficacy can be adapted to a particular olefin metathesis, preferably in which the substituents attached to W are selected such that TOF is improved compared to the known structure.

In a first aspect, the invention relates to a compound of formula I

I

wherein M is W;

R¹ is H, aryl, heteroaryl, alkyi, or heteroalkyi, optionally substituted, respectively;

R² and R³ can be the same or different and are hydrogen, alkyi, alkenyl, heteroalkyi, het- eroalkenyl, aryl, or heteroaryl, optionally substituted, respectively;

R⁵ is a residue R⁶-X-, wherein

R⁶ is alkyi, aryl, heteroalkyi, or heteroaryl, optionally substituted, respectively;

(R⁷, R⁸, R⁹)Si, wherein R⁷, R⁸, R⁹ are independently alkyi, alkoxy, phenyl or phenoxy, optionally substituted, respectively; (R¹⁰, R¹¹, R¹²)C, wherein R ⁰, R¹¹, R¹² are independently phenyl or alkyi, optionally substituted, respectively;

X = O, S, or NR¹³, wherein R¹³ is H or R ³ is alkyi or aryl, optionally substituted, re- spectively; or

R⁵ is a residue R⁶-CO-NR¹³, wherein R⁶ and NR ³ have the meaning as defined above, or wherein R⁶ and R¹³ taken together form a carbon chain having from 2 to 6 carbon atoms; or

R⁵ is a 4 to 8 membered N-containing ring, preferably N-containing carbon ring, wherein N is linked to M; and

R⁴ is a residue 0-Si(0-)₃, and represents silica to which M is linked forming a M-0-Si(0- )₃ moiety, preferably wherein silica is comprised in a solid support; under the proviso that a compound in which

R¹ = 2,6-diisopropylphenyl, R⁵ = 2,5-dimethylpyrrol-1 -yl, R² = tBu, and R³ = H is excluded.

Preferably, R¹, R², R³ and R⁵ are selected such that the compound of formula I exhibits in a metathesis reaction a turnover frequency that is higher than the turnover frequency that is achieved under the same reaction conditions with a compound of formula I in which R¹ = 2,6-diisopropylphenyl, R⁵ = 2,5-dimethylpyrrol-1-yl, R² = tBu and R³ = H.

In one embodiment, for assessing the efficacy of substituents R¹, R², R³ and R⁵, cis- 4-nonene is subjected to homo or self metathesis (SM).

In one embodiment, a compound of formula I is provided in which

R¹ is aryl or adamant-1-yl, optionally substituted, respectively; preferably wherein aryl is phenyl or naphthyl, or phenyl or naphthyl substituted with up to five substituents inde- pendently selected from C C alkyl, C-1-C4 alkoxy, CF₃, F, CI, Br, or phenyl or phenoxy, optionally substituted, respectively;

R² is -C(CH₃)₂C₆H5 or -C(CH₃)₃;

R³ is H;

R⁵ is a residue R⁶-X-, wherein

X = O and R⁶ is phenyl or phenyl substituted with up to five substituents independently selected from alkyl, preferably C C₄ alkyl, such as methyl, isopropyl or t-butyl; alkoxy, preferably C C₄ alkoxy; phenoxy, phenyl, optionally substituted, respectively; or halogen; or

X = S and R⁶ is phenyl or phenyl substituted with up to five substituents independently selected from alkyl, preferably C C₄ alkyl such as methyl, isopropyl or t-butyl; alkoxy, preferably Ci-C₄ alkoxy; phenoxy, phenyl, optionally substituted, respectively; or halogen; or

X = O and R⁶ is triphenylsilyl or triphenoxysilyl, optionally substituted, respectively; or th(d-C alkyl)silyl or tri(C C₄ alkoxy)silyl; or

X = O and R⁶ is triphenylmethyl, optionally substituted; or

X = O and R⁶ is 9-phenyl-fluorene-9-yl; or

X = O and R⁶ is 2-phenyl-1 ,1 ,1 ,3,3,3-hexafluoro-prop-2-yl [(C₆H₅)(CF₃)₂C]; or

X = O and R⁶ is t-butyl, optionally substituted with one or more F groups. In a further embodiment, a compound of formula I is provided in which

R is phenyl substituted with up to five substituents independently selected from C₁-C4 alkyl, C C₄ alkoxy, CF₃, F, CI, Br, or phenyl or phenoxy, optionally substituted, respectively;

R² is -C(CH₃)₂C₆H₅ or -C(CH₃)₃;

R³ is H; and

R⁵ is a residue R⁶-X-, wherein

X = O and R⁶ is phenyl or phenyl substituted with up to five substituents independently selected from C-i-C₄ alkyl, d-C alkoxy, phenoxy, phenyl, halogen; or

X = S and R⁶ is phenyl or phenyl substituted with up to five substituents independently selected from C C₄ alkyl, C C alkoxy, phenoxy, phenyl, halogen; or

X = O and R⁶ is triphenylsilyl, triphenoxysilyl, tri(Ci-C₄ alkyl)silyl or tri(C -C₄ alkoxy)silyl; or

X = O and R⁶ is t-butyl or t-butyl substituted with one or more F groups, preferably (CF₃)(CH₃)₂C, (CF₃)₂(CH₃)C, or (CF₃)₃C; or (C₆H₅)(CF₃)₂C; or

R⁵ is pyrrol-1-yl, 2,5-dimethylpyrrol-1-yl, or 2,5-diphenylpyrrol-1-yl.

In a preferred embodiment, R² is -C(CH₃)₂C₆H5. Moreover, the inventors of the present invention have surprisingly discovered that the efficacy of the catalyst according to the invention expressed in terms of TOF compared to the known structure can be improved by a purposive selection in particular of residues R¹ and R^s. Accordingly, in one preferred embodiment, a compound of formula I is provided in which R¹ is an electron donating group and R⁵ is an electron withdrawing group.

Preferably, a compound of formula I is provided in which

R¹ is phenyl substituted with up to five substituents independently selected from C C₄ alkyl, Ci-C alkoxy, phenyl, phenoxy;

R² is -C(CH₃)₂C₆H₅ or -C(CH₃)₃;

R³ is H; R^s is (CF₃)(CH₃)₂CO, (CF₃)2(CH₃)CO, (CF₃)₃CO, (C₆H₅)(CF₃)₂CO, pyrrol-1-yl, 2,5- dimethylpyrrol-1 -yl, or 2,5-diphenylpyrrol-1 -yl.

Preferably, R¹ is 2,6-diisopropylphenyl.

The inventors have further discovered that the object is also achieved if R¹ is an electron withdrawing group and R⁵ is an electron donating group.

Preferably, a compound of formula I is provided in which

R is phenyl substituted with up to five substituents independently selected from CF₃, F, CI, Br;

R² is -C(CH₃)2C₆H5 or -C(CH₃)₃;

R³ is H;

R⁵ is (CH₃)₃CO, tri(C₁-C₄ alkyl)silyloxy, tri(phenyl)silyloxy, tri(C₁-C₄ alkoxy)silyloxy, or tri(phenoxy)silyloxy, or phenoxy or phenylthio, wherein the phenyl moiety may be substituted with up to five substituents independently selected from Ci-C₄ alkyl, C-_\-C₄ alkoxy, phenoxy, phenyl, halogen.

A preferred triiCr^ alkoxyJsilyloxy residue is tris-(t-butoxy)silyloxy.

Preferably, R is 2,6-dichlorophenyl, pentafluorophenyl, 2-(trifluoromethyl)phenyl or 2,6- di(trifluoromethyl)phenyl.

In a further preferred embodiment, catalysts in which both R and R⁵ are electron withdrawing groups may also be used for the heterogeneous catalysis of metathesis reactions.

Compounds in which both R¹ and R⁵ are electron withdrawing groups preferably have a structure in which

R¹ is phenyl substituted with up to five substituents independently selected from CF₃, F, CI, Br;

R² is -C(CH₃)₂C₆H₅ or -C(CH₃)₃; R³ is H;

R⁵ is (CF₃)(CH₃)₂CO, (CF₃)₂(CH₃)CO, (CF₃)₃CO, (C₆H₅)(CF₃)₂CO, pyrrol-1-yl, 2,5- dimethylpyrrol-1 -yl, 2,5-diphenylpyrrol-1-yl. Preferably, R is 2,6-dichlorophenyl, pentafluorophenyl, 2-(trifluoromethyl)phenyl or 2,6- di(trifluoromethyl)phenyl.

The compounds according to the invention of formula I may be prepared by grafting appropriate precursor compounds on silica or on a support comprising silica.

Preferably, a silica is used which is partially dehydroxylated and dehydrated. Preferably, silica is dehydroxylated and dehydrated at elevated temperature, preferably at elevated temperature and in vacuo. Preferably, silica is partially dehydroxylated and dehydrated at 700 °C (Si0_{2-( 0}o))- However, other temperatures or temperature ranges may also be used depending on the requirements of the compound of formula I to be used as heterogeneous catalyst.

Suitable precursor compounds for the preparation of compounds of formula I are e.g. compounds of formula I in which R⁴ is a ligand that can be replaced by a 0-Si(0-)₃ moiety. Suitable ligands are preferably alkoxy and 2,5-dimethylpyrrol-1-yl ligands. Suitable precursor compounds are known or may be prepared according to known methods.

The compounds according to the invention may be used in the various known types of metathesis reaction.

Thus, according to a second aspect, the invention relates to a method of forming an olefin from a first olefin and a second olefin in a metathesis reaction, comprising step (i): (i) reacting the first olefin with the second olefin in the presence of a compound as defined in the first aspect. The structure of the first and the second olefin may be vastly freely selected. Preferably, (a) the first olefin and the second olefin are identical [homo or self-metathesis (SM)]; or

(b) the first and the second olefin are different from one another [cross metathesis (CM)]; or

(c) the first olefin has an internal olefinic double bond and the second olefin is ethylene [ethenolysis]; or

(d) the first olefin is a cyclic olefin and the second olefin is a cyclic olefin, wherein the first and the second olefin may be identical or may be different from one another [cross metathesis (SM) or (CM)]; or

(e) the first olefin is a diene and the second olefin is a diene, wherein the first olefin and the second olefin are identical, wherein step (i) results in the ring closing of the diene [ring closing metathesis (RCM)]; or

(f) the first olefin is a cyclic olefin and the second olefin is a cyclic olefin, wherein the first olefin and the second olefin are identical, wherein step (i) results in a ring opening metathesis polymerization (ROMP); or

(g) the first olefin is a terminal diene and the second olefin is a terminal diene, wherein the first olefin and the second olefin are identical, and wherein step (i) results in a acyclic diene metathesis polymerization (ADMET), wherein a polyene and ethylene are generated.

Preferably, the method according to step (i) is carried out in a solvent, which dissolves the olefins and suspends the catalyst. Suitable solvents are solvents selected from aromatic solvents, preferably toluene, halogenated solvents, preferably chlorobenzene or methylene dichloride, alkanes, preferably pentane or hexane or octane. However, step (i) may be carried out without solvent, preferably if one of the olefins is a liquid under the reaction conditions. A reaction of the first and the second olefin in gaseous phase is likewise possible or the first olefin is in gaseous phase and the second olefin is in liquid phase. The temperature employed in step (i) preferably ranges from - 20 °C to 200 °C, more preferably from 0 °C to 110 °C, still more preferably from 15 to 50 °C.

The concentration of the compound according to the invention used as catalyst in the method according to the invention can vary in broad ranges. Preferably, the catalyst is employed in a molar ratio of < 5 mol % (calculated in terms of W), based on the first or the second olefin (100 mole %).

The proceeding of the reaction may be controlled preferably by gas chromatographic methods.

Preferably, the reaction is terminated by separating off the catalyst from the reaction mixture obtained in step (i). Separating off may be performed by methods such as filtration or centrifugation or distilling off the reaction mixture from the catalyst.

It has been surprisingly found that the compounds according to the invention after the separating off may be re-used in the reaction according to step (i) without considerable loss of activity and selectivity. This makes the compounds according to the invention particularly advantageous over respective homogeneous catalysts, which frequently require a complex processing of the reaction mixture obtained from metathesis, wherein the catalysts are often destroyed or at least considerably deteriorated in their activity.

Thus, the compounds according to the invention perform particularly beneficial at an industrial scale.

Accordingly, in one embodiment, the method according to the invention further comprises at least step (ii) or step (ii) and step (iii):

(ii) separating off the compound according to the invention from the reaction mixture obtained in step (i), preferably by filtration or centrifugation or distilling off the reaction mixture from the compound according to the invention;

(iii) re-using in step (i) the catalyst obtained in step (ii). The metathesis reaction typically proceeds via a complex formation of the compound according to the invention with the first or the second olefin. Preferably, the reactions proceeds further via a metallacyclobutane formation, wherein the formed metallacyclobu- tane may be isolated.

Thus, according to a third aspect, the invention relates to an addition product of the compound as defined in the first aspect with the first olefin or the second olefin as defined in the second aspect, wherein the addition product is (a) a product in which the first or the second olefin as defined in the second aspect forms via its olefinic double bond together with the compound as defined in the first aspect a metallacyclobutane moiety, and R² and R³ are attached to the metallacyclobutane ring. According to a fourth aspect, the invention relates to the use of a compound as defined in the first aspect or in the third aspect in a metathesis reaction.

Preferably, the metathesis reaction is selected from the group consisting of self- metathesis (SM), cross metathesis (CM), ring opening metathesis (ROM), ring closing metathesis (RCM), ring opening metathesis polymerization (ROMP), ethenolysis, and acyclic diene metathesis polymerization (ADMET).

Definitions used in the meaning of the invention The catalyst according to the invention is heterogeneous, i.e. it comprises a solid support. Said solid support comprises "silica" or consists of "silica".

A solid support may be any material that includes silica such as silica as such or silica in combination with other materials. Accordingly, silica may be used in the form of a mixed oxide, e.g. a mixed oxide of silica and alumina or silica and zirconia. Preferably, silica is used as such as solid support.

The term "silica" further encompasses porous or non-porous silica. The term further encompasses partially dehydroxylated and/or dehydrated silica. Dehy- droxylation and/or dehydration may be performed using elevated temperature or elevated temperature and vacuum. Residual hydroxyl content may be determined by titration with MeMgCI.

Hydroxyl content may be freely selected depending on drying temperature and drying time. Accordingly, the silica used for the compounds according to the invention may be adjusted in a tailor-made manner to the required properties of the W-compound to be immobilized. In this regard it is noteworthy that depending on the number of mmol of hy- droxyl groups per gram silica, the amount of W compound per gram of silica and ultimately the activity of the resulting catalyst may be adjusted depending upon needs.

In a preferred embodiment, silica is subjected to a temperature in the range of from 400 to 800 °C for a period ranging from 4 to 24 under pressure ranging from 10^~6 mbar to 1 bar. Temperature and pressure may be performed in ramps.

Preferably, hydroxyl content determined by means of titration with MeMgCI ranges from 0.05 mmol to 2.00 mmol per g silica, further preferred from 0.1 mmol to 1 mmol per g silica.

The term "metathesis" refers to alkene (olefin) metathesis.

The term "cross metathesis" encompasses the reaction between two different olefins. The term "ring opening metathesis" encompasses the ring opening of a cyclic alkene.

The term "ring opening polymerization metathesis" encompasses the ring opening of a cyclic alkene, wherein the ring-opened product polymerizes in a chain-growth polymerization to form a polymer containing olefinic bonds.

The term "ring closing metathesis" encompasses the ring closing of a diene. The term "ethenolysis" encompasses the reaction of an olefin having an internal olefinic bond with ethylene.

The term "self or homo metathesis (SM)" encompasses the reaction between two identi- cal olefins. The term is synonymously used with the term "homo cross metathesis (HCM)" and also encompasses the formation of an internal olefin from two identical olefins.

The term "turnover frequency (TOF)" defines the number of turnovers of moles of olefin per time unit of a certain catalyst.

The term "electron withdrawing" or "electron withdrawing group (EWG)" encompasses a group which draws electrons away from the central W of the compound according to the invention.

The term "electron donating group" or "electron dono encompasses a group which donates electrons to the central W of the compound according to the invention.

The person skilled in the art is familiar with terms such as "electron withdrawing group (EWG)" or "electron donor" and can residues R¹ and R⁵ attribute to the respective properties.

The term "olefinic double bond' refers to a carbon-carbon double bond or ethylenic double bond in a first olefin and a second olefin.

The term "olefin" as used in the terms "first olefin" and "second olefin" refers to any species having at least one ethylenic double bond such as linear and branched chain aliphatic olefins, cycloaliphatic olefins, or aryl substituted olefins. Olefins may comprise terminal double bond(s) {"terminal olefin") and/or internal double bond(s) ("internal ole- fin") and can be cyclic or acyclic, linear or branched, optionally substituted. The total number of carbon atoms can be from 2 to 100, or from 2 to 40; the double bonds of a terminal olefin may be mono- or bi-substituted and the double bond of an internal olefin may be bi-, tri-, or tetrasubstituted. In some cases, an internal olefin is bisubstituted. Non-limiting examples of terminal olefins are substituted and unsubstituted linear alkyl internal olefins such as C₄-C₃₀ olefins (e.g., 1-butene, 1-pentene, 1-hexene, 1 -heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1- eicosene, allylbenzene, allyltrimethylsilane, methyl-10-undecenoate, allylboronic acid pincol ester, allylbenzylether, N-allyl-4-methylbenzenesulfonamide, allylaniline, methyl-9- decenoate, allyloxy(tert-butyl)dimethyl silane, allylcyclohexane, etc.).

In one embodiment, the olefin having a terminal olefinic double bond is of formula RCH=CH₂, wherein R is selected from H, alkyl, alkenyl, aryl, heteroalkyl, heteroalkenyl, heteroaryl, or acyl, optionally substituted.

In one embodiment, the olefin is a polyisoprene. The term "cyclic olefin" refers to any cyclic species comprising at least one ethylenic double bond in a ring. The atoms of the ring may be optionally substituted. The ring may comprise any number of carbon atoms and/or heteroatoms. In some cases, the cyclic olefin may comprise more than one ring. A ring may comprise at least 3, at least 4, at least 5, at least 6, at least 7, at least 8, or more, atoms. Non-limiting examples of cyclic olefins include norbornene, dicyclopentadiene, bicyclo compounds, oxabicyclo compounds, and the like, all optionally substituted. "Bicyclo compounds" are a class of compounds consisting of two rings only, having two or more atoms in common. "Oxabicyclo compounds" are a class of compounds consisting of two rings only, having two or more atoms in common, wherein at least one ring comprises an oxygen atom.

In another embodiment, the first and the second olefin or the first and the second olefin may bear one or more functional groups.

Preferably, the first and the second olefin or the first or the second olefin may bear one or more functional groups independently selected from the group consisting of ether, ester, amide, amine, halogen, nitrile, thioether, thioester, aryl, or heteroaryl. ln a further preferred embodiment, the first and the second olefin or the first or the second olefin bear one or more functional groups independently selected from alkoxy, ar- yloxy, perhaloalkoxy, arylalkoxy, heteroaryl, heteroaryloxy, heteroarylalkyl, het- eroarylalkoxy, amino, halogen, alkylthio, oxo, carboxy esters, carboxamido, acyloxy, aminoalkyl, alkylaminoaryl, alkylaminoalkyl, alkoxyaryl, arylamino, arylalkylamino, alkyl- sulfonyl, carboxamidoalkylaryl, carboxamidoaryl, hydroxyalkyl, haloalkyl, alkylaminoal- kylcarboxy-, aminocarboxamidoalkyl-, cyano, alkoxyalkyl, perhaloalkyl, arylalkyloxyalkyl.

The term "alkyf encompasses saturated aliphatic groups, including straight-chain alkyl groups, branched-chain alkyl groups, cycloalkyl (alicyclic) groups, alkyl substituted cy- cloalkyl groups, and cycloalkyl substituted alkyl groups and alkyl groups substituted with aryl. In certain embodiments, a straight chain or branched chain alkyl has about 30 or fewer carbon atoms in its backbone (e.g., Ci-C₃₀ for straight chain, C₃-C₃o for branched chain), and alternatively, about 20 or fewer. Likewise, cycloalkyls have from about 3 to about 10 carbon atoms in their ring structure, and alternatively about 5, 6 or 7 carbons in the ring structure. In some embodiments, an alkyl group may be a lower alkyl group, wherein a lower alkyl group comprises 10 or fewer carbon atoms in its backbone (e.g., C1-C10 for straight chain lower alkyls). In one embodiment, the term "alkyf encompasses C1-C4 alkyl such as methyl, isopropyl iPr) or t-butyl (tBu).

The term "alkyf also encompasses bridged hydrocarbon residues such as the adamantyl residue, particularly the adamant-1-yl residue.

The term "alkyf also encompasses anellated ring systems such as the fluorene-9-yl residue such as the 9-phenyl-fluorene-9-yl residue.

The term "t-Bu" denotes a tertiary butyl group (CH₃)₃C.

The term "tBu_F3" denotes a tertiary butyl group (CF₃)(CH₃)₂C. The term "tBu_F6 denotes a tertiary butyl group (CF₃)₂(CH₃)C. The term "tBupg" denotes a tertiary butyl group (CF₃)₃C. The term "alkoxy" refers to the group -O-alkyl, wherein alkyl has the meaning as defined above in connection with the term alkyl.

The term "alkenyf refers to olefinic groups as described above. The alkenyl group may be optionally substituted with the substituents defined above.

The term "aryf refers to aromatic carbocyclic groups, optionally substituted, having a single ring (e.g., phenyl), multiple rings (e.g., biphenyl), or multiple fused rings in which at least one is aromatic (e.g., 1 ,2,3,4-tetrahydronaphthyl, naphthyl, anthryl, or phenanthryl). That is, at least one ring may have a conjugated π electron system, while other, adjoining rings can be cycloalkyls, cycloalkenyls, cycloalkynyls, aryls, and/or heterocyclyls. The aryl group may be optionally substituted, as described herein.

The term "carbocyclic aryl groups" as used herein refers to aryl groups wherein the ring atoms on the aromatic ring are carbon atoms. Carbocyclic aryl groups include monocyclic carbocyclic aryl groups and polycyclic or fused compounds (e.g., two or more adjacent ring atoms are common to two adjoining rings) such as naphthyl groups. In some cases, the aryl groups may include monocyclic carbocyclic aryl groups and polycyclic or fused compounds (e.g., two or more adjacent ring atoms are common to two adjoining rings) such as naphthyl group. Non-limiting examples of aryl groups include phenyl, naphthyl, tetrahydronaphthyl, indanyl, indenyl, and the like.

A preferred aryl residue is 2,6-diisopropylphenyl as residue R¹. A further preferred aryl residue is 2,6-dichlorophenyl as residue R¹ or pentafluorophenyl, 2- (trifluoromethyl)phenyl or 2,6-di(trifluoromethyl)phenyl.

The term "phenoxy" refers to the group C₆H₅0 -.

The term "thiophenoxy" or "phenylthio" refers to the group C₆H₅S -.

This phenoxy or thiophenoxy residue may be substituted with up to five substituents independently selected from alkyl, preferably C1-C4 alkyl such as methyl, isopropyl or t- butyl, alkoxy, preferably C^C₄ alkoxy, phenoxy, phenyl, halogen. A preferred phenoxy residue is 2,6-diphenylphenoxy as residue R⁵ or 4-fluoro-2,6- dimesitylphenoxy or 2,6-di-tert.-butylphenoxy 4-bromo-2,6-di-tert.-butylphenoxy or 4- methoxy-2,6-di-tert.-butylphenoxy or 4-methyl-2,6-di-tert.-butylphenoxy or 2,4,6-tri-tert.- butylphenoxy or 2,3,5,6-tetraphenylphenoxy or 4-bromo-2,3,5,6-tetraphenylphenoxy or 2,6-di(4-bromophenyl)-3,5-diphenylphenoxy or 4-bromo-2,6-di(4-bromophenyl)-3,5- diphenylphenoxy.

A preferred thiophenoxy residue is 2,6-diphenylthiophenoxy, 4-bromo-2,6- diphenylthiophenoxy, 4-fluoro-2,6-diphenylthiophenoxy, 4-methyl-2,6- diphenylthiophenoxy, 2,4,6-triphenylthiophenoxy, 4-fluoro-dimesitylthiophenoxy, 2,6-di- tert.-butylthiophenoxy, 4-bromo-2,6-di-tert.-butylthiophenoxy, 4-methoxy-2,6-di-tert.- butylthiophenoxy, 4-methyl-2,6-di-tert.-butylthiophenoxy, 2,4,6-tri-tert.-butylthiophenoxy, 2,3,5,6-tetraphenylthiophenoxy, 4-bromo-2,3,5,6-tetraphenylthiophenoxy, 2,6-di(4- bromophenyl)-3,5-diphenylthiophenoxy, 4-bromo-2,6-di(4-bromophenyl)-3,5- diphenylthiophenoxy as residue R⁵.

The term "heteroaryi' as used herein refers to aryl groups as described herein in which one or more atoms is a heteroatom (e.g., oxygen, nitrogen, sulfur, and the like), optionally substituted. Examples of aryl and heteroaryi groups include, but are not limited to, phenyl, aryloxy, pyrrolyl, furanyl, thiophenyl, imidazolyl, oxazolyl, thiazolyl, triazolyl, pyra- zolyl, pyridinyl, pyrazinyl, pyridazinyl and pyrimidinyl, and the like.

A preferred heteroaryi residue as residue R⁵ is the pyrrol-1 -yl residue (py) or 2,5- dimethylpyrrol-1-yl (2,5-Me₂py or Me₂pyr) or 2,5-diphenylpyrrol-1-yl. The pyrrol-1 -moiety is also termed as pyrrolide.

The term "heteroalkyr refers to alkyl groups as described herein in which one or more atoms is a heteroatom (e.g., oxygen, nitrogen, sulfur, and the like). Examples of het- eroalkyl groups include, but are not limited to, alkoxy, poly(ethylene glycol)-, alkyl- substituted amino, tetrahydrofuranyl, piperidinyl, morpholinyl, etc.

The term "halogen" refers to F, CI, Br, I. The term "acyf refers to H, alkyl, alkenyl, aryl, heteroalkyl and heteroaryl groups as defined above, which are linked to another atom or to another moiety such as a olefinic double bond via a carbonyl group. The term "triphenylsilyloxy" refers to preferred group (C₆H₅)₃SiO, wherein the phenyl residue may be substituted. The term "triphenoxysilyloxy" refers to group (C₆H₅0)₃SiO, wherein the phenyl residue may be substituted.

The term "trialkylsilyloxy" refers to preferred group (Ci _ C₄)₃SiO, wherein the alkyl resi- due may be substituted. The term "trialkoxysilyloxy" refers to group (Ci _ C₄ 0)₃SiO, wherein the alkoxy residue may be substituted.

The term "comprising" is used in the meaning of "including but not limited to". The term "consisting of is used in the meaning "including and limited to".

The term "first or second olefin" is in one embodiment synonymously used with the term "first and second olefin". The term "chemical reaction" encompasses a reaction in which in a compound a new bond is formed.

The terms "substituted' and "optionally substituted" are contemplated to include all permissible substituents of organic compounds, "Permissible" being in the context of the chemical rules of valence known to those of ordinary skill in the art. Examples of substituents include, but are not limited to, alkyl, aryl, arylalkyl, cyclic alkyl, heterocycloalkyl, hydroxy, alkoxy, aryloxy, perhaloalkoxy, arylalkoxy, heteroaryl, heteroaryloxy, het- eroarylalkyl, heteroarylalkoxy, azido, amino, halogen, alkylthio, oxo, acylalkyi, carboxy esters, carboxyl, -carboxamido, nitro, acyloxy, aminoalkyl, alkylaminoaryl, alkylaryl, al- kylaminoalkyl, alkoxyaryl, arylamino, arylalkylamino, alkylsulfonyl, -carboxamidoalkylaryl, -carboxamidoaryl, hydroxyalkyl, haloalkyl, alkylaminoalkylcarboxy-, aminocarboxami- doalkyl-, cyano, alkoxyalkyl, perhaloalkyl, arylalkyloxyalkyl. ln one embodiment, the term "R⁶-CO-NR¹³ means a 4 to 8 membered cyclic carbon- and N-containing ring in which N is linked to M.

The term "N-containing carbon ring" means that the ring contains besides carbon atoms at least one nitrogen atom.

Examples

1. General procedures

All experiments were carried out under dry and oxygen free argon or nitrogen atmosphere using either standard Schlenk or glove-box techniques for organometallic synthesis. For the syntheses, reactions were carried out using high vacuum lines (1 fJ⁵ mBar) and glove-box techniques. Pentane, toluene and diethyl ether were purified using double MBraun SPS alumina column, and were degassed using three freeze-pump-thaw cycles before being used. DME and THF were distilled from Na/benzophenone. Silica (Aerosil Degussa, 200 m²g^"1) was compacted with distilled water, calcined at 500°C under air for 4 h and treated under vacuum (10^~5 mBar) at 500°C for 12 h and then at 700°C for 4 h (support referred to as Si0_2-(7oo)) and contained 0.26 mmol of OH per g as measured by titration with MeMgCI. For the Synthesis of Precursor Example 4, commercially available n-pentane contains was washed with cc. H₂S0₄ / cc. HN0₃ dried over CaCI₂ for one week before distillation on potassium metal. All infrared (IR) spectra were recorded using a Bruker spectrometer placed in the glovebox, equipped with OPUS software. A typical experiment consisted in the measurement of transmission in 32 scans in the region from 4000 to 400 cm^"1. The ¹H and ¹³C-NMR spectra were obtained on Bruker DRX 200, DRX 250 or DRX 500 spectrometers. The solution spectra were recorded in C₆D₆ at room temperature. The H and ³C chemical shifts are referenced relative to the residual solvent peak. Compounds [W(NAr)(CHCMe₃)(OtBu)₂],¹ [W(NAr)(CHCMe₃)(OtBu_F3)₂],¹ [W(NAr)(CHCMe₃)(OtBu_F6)₂],¹ [W(NArci)(CHCMe₂Ph)(Me₂Pyr)₂],² [W(NAr_Ci)(CHCMe₃)(OtBu_F6)₂]² and [(≡SiO)W(NAr)(CHCMe₃)(Me₂Pyr)]³ were synthe- sized according to literature procedures. Further precursors (starting materials) may be prepared according to such procedures or according to methods specified in the following.

Anhydrous solvents in the glovebox were stored over activated 3 A molecular sieves. NMR solvents were also stored over activated 3 A molecular sieves. Purification of other chemicals is described at the corresponding reactions. Celite® and 3 A molecular sieves were dried at approx. 300 °C under high vacuum ca. 0.1-0.5 mm Hg for a day (Schlenk- bomb, vacuum-line) to remove traces of water. All pieces of glassware were dried in an oven before use (120 °C). Cooling to -40 °C (-35 °C or -30 °C in some literature procedures) means storing in the glovebox fridge for at least half an hour. The synthesized complexes were stored in the glovebox's freezer at -40 °C. ¹ Schrock, R. R.; De Pue, R. T.; Feldman, J.; Yap, K.B.; Yang, D. C; Davis, W. M.; Park, L; Dimare, M.; Schofield, M.; Anhaus, J.; Walborsky, E.; Evitt, E.; Kriiger, C; Betz, P. Organometallics 1990, 2262.

² Arndt, S.; Schrock, R. R.; Miiller, P. Organometallics 2007, 1279.

³ Blanc, F.; Berthoud, R.; Coperet, C; Lesage, A.; Emsley, L; Singh, R.; Kreickmann, T.; Schrock, R. R. Proc. Nat. Acad. Sci. 2008, 12123.

Abbreviations:

THF = tetrahydrofuran

DME = 1 ,2-dimethoxyethane

Et₂0 = diethyl ether

TfOH = trifluoromethanesulfonic acid

LiMe₂Pyr =lithium 2,5-dimethylpyrrolide

2. Syntheses 2.1 Synthesis of precursors:

Precursor Example 1 : [W(NAr)(CHCMe₃)(OtBu_F9)2], Ar = 2,6-iPr₂C₆H₃

A cold (-40 °C) suspension of (CF₃)₃COLi (148 mg, 0.61 mmol, 2 equiv.) in diethyl ether (2 mL) was added to a solution of 250 mg of [W(NAr)(CHCMe₃)(OTf)₂(DME)] (0.305 mmol, 1.05 equiv.) in cold diethyl ether (6 mL, -40 °C) while stirring. The dark red solu- tion was stirred for 2h at room temperature, and the volatiles were removed under reduced pressure. The dark red solid was suspended in pentane (4 mL) and filtered on Celite® to afford a clear orange solution. The filtrate was taken to dryness in vacuo, and the orange powder dissolved back in pentane (2 mL). This drying/dissolution cycle was repeated four consecutive times, in order to remove all the coordinated DME molecules. Finally, the orange powder was solubilized in a minimum amount of pentane, and stored at -40 °C to give orange crystals, that were washed with cold (-40 °C) pentane, affording after drying in vacuo 218 mg of [W(NAr)(CHCMe₃)(OtBu_F9)2] (0.21 mmol, 69%). ¹H NMR (200 MHz, C₆H₆) δ (ppm) 9.45 (s, 1 H, CHCMe₃), 7.04-6.94 (m, 3H, Ar), 3.46 (2H, septet, CHMe₂), 1.15 (d, 12H, CHMe₂), 1.06 (s, 9H, CHCMe₃).¹⁹F NMR (200 MHz, C₆D₆) δ (ppm) -73.1 (s, 18F, C(C ₃))

Precursor Example 2: rW(NAr_Ci)(CHCMe₂Ph)(OtBu_F9)2(DME)], Ar_Ci = 2,6-ΟΙ-0₆Η₃

A cold (-40 °C) suspension of (CF₃)₃COLi (162.4 mg, 0.67 mmol, 2 equiv.) in diethyl ether (4 mL) was added to a suspension of 250 mg of [W(NArci)(CHCMe₂Ph)(OTf)2(DME)] (0.33 mmol, 1 equiv.) in cold diethyl ether (6 mL, - 40 °C) while stirring. The dark brown reaction mixture was stirred for 1 .5 h at room temperature, and the volatiles were removed under reduced pressure, affording a light brown solid. The solid was extracted in pentane (15 mL), filtered on Celite® and rinsed with pentane (2 x 5 mL). The volume of the filtrate was reduced to ca. 2 mL in vacuo and was stored at -40 °C, affording an orange powder. The powder was filtered and rinsed with cold (-40°C) pentane (2 x 1 mL) to afford after drying in vacuo 165.2 mg of an orange powder of the title compound (0.159 mmol, 48 %). Single crystals suitable diffraction studies of [W(NAr_Ci)(CHCMe₂Ph)(OtBu_F9)2] were grown in -40°C toluene. ¹H NMR (300 MHz, C₆H₆) δ (ppm) 9.61 (s, 1 H, CHCMe₃), 7.45 (m, 2H, Ph), 7.00 (m, 2H, Ph), 6.74 (m, 1 H, Ph), 6.69 (d, 2H, Ar, J = 8.1 Hz), 6.19 (t, 1 H, Ar, J = 8.2 Hz), 3.00 (s, 6H, DME), 2.87 (s, 4H, DME), 1.44 (s, 6H, CHCMe₂Ph). ¹⁹F NMR (300 MHz, C₆D₆) δ (ppm) -73.1 (s, 18F, C(CF₃)).

Precursor Example 3: [W(NAr_Ci)(CHCMe₂Ph)(OtBu)2], Ar_c, = 2,6-CI-C₆H₃

To a cold THF solution (-41 °C, 20 mL) of [W(NAr_Ci)(CHCMe₂Ph)(Me₂Pyr)₂] (200 mg, 0.30 mmol, 1 equiv.) was added dropwise over 1 h a solution of tBuOH (44.6 mg, 0.60 mmol, 2 equiv.) in cold THF (-41 °C, 10 mL). The resulting brown solution was further stirred overnight in the MeCN/C0₂ bath, slowly reaching room temperature. The resulting dark brown solution was dried in vacuo (2 h, 10^"2 mBar). The brown residue was extract- ed in cold pentane (-40 °C, 3 mL), filtered on Celite® and evaporated to dryness to afford 108 mg of an oily orange solid (0.173 mmol, 57 %). ¹H NMR (300 MHz, C₆H₆) δ (ppm) 8.09 (s, 1 H, CHCMe₂Ph), 7.54 (m, 2H, Ph), 7.16 (m, 2H, Ph), 7.08 (m, 1 H, Ph), 6.97 (m, 2H, Arc,), 6.31 (t, 1 H, Ar_Ci, J = 8.2 Hz), 1.72 (s, 6H, CHC e₂Ph), 1.26 (s, 18H, OCMe₃).

Precursor Example 4: [W(NAr_CF3)(CHC e2Ph)(Me₂Pyr)2], (Ar_CF3 = 2-CF₃-C₆H₄, e₂Pyr = 2,5-dimethylpyrrolide) a) Synthesis of W(NAr-2-CF₃)₂CI₂(DME)

A 100 mL three-necked round-bottomed flask was equipped with a magnetic stirring bar, thermometer and a gas inlet adapter. The flask was charged with W0₂CI₂ (1.74 g, 6.07 mmol) and DME (20 mL) in a N₂ filled glovebox resulting in a deep blue homogenous solution. The flask was chambered out of the glovebox and connected to a N2 - vacuum dual manifold. To the blue homogenous solution Me₃SiCI (6.59 g, 7.70 mL, 60.68 mmol) and 2,6-lutidine (2.93 g, 3.18 mL, 27.31 mmol) followed by 2-trifluoromethylaniline (1.96 g, 1.53 mL, 12.14 mmol) were added at ambient temperature under a positive nitrogen flow. Upon the addition of the 2-trifluoromethylaniline copious amount of precipitate crashed out of the solution. The dense orange-yellow suspension was stirred for 30 min at room temperature. The gas inlet was opened towards the nitrogen-vacuum manifold thus the mercury bubbler provided a slight nitrogen pressure over the reaction mixture. The mixture was heated to 75 °C and stirred for 17 h. Volatiles were removed in vacuo through the vacuum-line, temperature was maintained at 30-40 °C by careful heating. The remaining solid was transferred back into the glovebox. The solid was mixed with DME (20-40 mL) and the suspension was filtered through a pad of Celite®. The Celite® pad was carefully washed with DME until the filtrate was colorless. The filtrate was evaporated to dryness resulting in an orange-red solid. The resulting solid was triturated with n-pentane thoroughly. Solid material was filtered off (sintered glass-filter funnel) and allowed to dry on the filter funnel while the nitrogen stream was kept going to afford the product as an orange solid (3.65 g, 91 %).

¹H NMR (300 MHz, C₆D₆): δ 7.55 (d, 2, aromatic), 7.30 (d, 2, aromatic), 6.89 (t, 2, aro- matic), 6.38 (t, 2, aromatic), 3.46 (s, 6, MeOCH₂CH₂OAfe), 3.01 (s, 4, MeOCH₂CH₂OMe). ¹⁹F NMR (300 MHz, C₆D₆): δ -61.30 (s, 3F, ArCF₃). b) Synthesis of W(NAr-2-CF₃)₂(CH₂CMe₂Ph)₂

In a N₂ filled glovebox a 100 mL round-bottomed flask was equipped with a magnetic stirring bar. The flask was charged with W(NAr-2-CF₃)₂CI₂(DME) complex (3.65 g, 5.50 mmol) and the complex was mixed with diethyl ether (70 mL) resulting in an orange sus- pension. The Grignard-reagent solution, PhMe₂CCH₂MgCI (5.91 mL, 12.1 1 mmol; 2.05 M in Et₂0) was added dropwise to the etheral mixture of W(NAr-2-CF₃)₂CI₂(DME) complex at rt. The reaction mixture turned to yellow and a white precipitate formed. The reaction mixture was stirred overnight. The progress of the reaction was checked by ¹H NMR by taking sample from the reaction mixture. The reaction mixture was filtered through Celite®, and the solid was carefully washed with diethyl ether (30 mL) until the filtrate was colorless affording a yellow homogenous solution. The filtrate was evaporated to dryness, and the residue was extracted with n-pentane (100-150 mL), filtered through a pad of Celite® and washed with n-pentane (40 mL). The filtrate was concentrated approximately to one third and left standing at -30°C for crystallization. The solid was fil- tered off, washed with small portions of cold n-pentane (-40 °C) and dried on the frit in nitrogen stream to afford the product as a yellow solid (3.12 g, 74%).

¹H NMR (300 MHz, C₆D₆): δ 7.35 (m, 6, aromatic), 7.12 (m, 4, aromatic), 6.99 (t, 2, aromatic), 6.77 (m, 4, aromatic), 6.53 (t, 2, aromatic), 1.84 (s, 4, CH₂CMe₂Ph), 1.43 (s, 12, CH₂C e₂Ph). ⁹F NMR (300 MHz, C₆D₆): δ -61.32 (s, 3F, ArCF₃). c) Synthesis of W(NAr-2-CF₃)(CHCMe₂Ph)(OTf)₂(DME):

The reaction was carried out in a N₂ filled glovebox. In the glovebox a 100 mL round- bottomed flask was equipped with a magnetic stirring bar. The flask was charged with W(NAr-2-CF₃)₂(CH₂CMe₂Ph)₂ complex (2.00 g, 2.60 mmol). The starting complex was dissolved in a mixture of DME (15 mL) and Et₂0 (50 mL) and the obtained yellow solution was cooled to -30 °C. In the meantime TfOH was cooled to -30 °C (still in the ampule). A small vial was charged with Et₂0 (6 mL) and cooled to -30 °C. The cold TfOH (1.17 g, 0.69 mL, 7.81 mmol) was added to the chilled Et₂0 and this cooled premix was transferred (in 5 min.) to the stirred, cold solution of the starting W-complex. The reaction mixture was allowed to warm to ambient temperature and stirred overnight. Upon overnight stirring the mixture's color turned to orange-yellow. The reaction was monitored by ¹H NMR spectroscopy. Solvents were evaporated under vacuum and the resulting yel- lowish solid was mixed with cold toluene (50 mL). The mixture was filtered through a pad of Celite® and washed with cold toluene (20 mL) thoroughly until the filtrate was almost colorless. The filtrate was evaporated to dryness and the resulting orange-red gummy material was mixed with mixture of diethyl ether and n-pentane (10 mL). The solution was left standing at -30 °C, affordinga yellow solid. The solid was separated by vacuum filtration, washed with small portions of mixture of diethyl ether and n-pentane (-40 °C) and dried in a nitrogen stream. The product is a light yellow powder (1 .1 1 g, 49%).

Cis isomer (major); ¹H NMR (300 MHz, C₆D₆): δ 1 1.96 (s, 1 , CHCMe₂Ph), 7.99 (d, 1 , aromatic), 7.41 (d, 2, aromatic), 3.26 (s, 3, OCH₃), 3.25 (m, 1 , OCH₂), 3.03 (s, 3, OC/-/₃), 2.94 (m, 2, OCH₂), 2.53 (m, 1 , OCH₂), 1.89 (s, 3, CMe₂Ph), 1.63 (s, 3, C e₂Ph). ¹⁹F NMR (300 MHz, C₆D₆): δ -60.18 (s, 3F ArCF₃), -76.82 (m, 3F -S0₂CF₃), -77.98 (m, 3F - S0₂CF₃).

Trans isomer (minor); ¹H NMR (300 MHz, C₆D₆): δ 10.92 (s, 1 , CHCMe₂Ph), 7.76 (d, 1 , aromatic), 7.62 (d, 2, aromatic), 3.45 (s, 3, OCH₃), 3.23 (m, 2, OCH₂), 2.87 (s, 3, OCH₃), 2.75 (m, 2, OCH₂), 1.87 (s, 6, C/lfe₂Ph). ¹⁹F NMR (300 MHz, C₆D₆): δ -61.71 (s, 3F ArCF₃), -77.18 (m, 6F -S0₂CF₃). d) Synthesis of W(NAr-2-CF₃)(CHCMe₂Ph)(2,5-diMePyrr)₂

A cold suspension of 47.5 mg of LiMe₂Pyr (0.47 mmol, 2 equiv.) in toluene (-40 °C, 3 mL) was added dropwise under stirring to a cold toluene solution (-40°C, 8 mL) of [W(NAr_CF3)(CHCMe₂Ph)(OTf)₂(DME)] (203 mg, 0.23 mmol, 1 equiv.). The suspension was stirred overnight, affording an orange solution and an off-white precipitate. The solution was filtered on Celite®, affording a clear orange solution, and taken to dryness to yield a dark orange oil. This oil was triturated with cold (- 40°C) pentane (2 x 1.5 mL) to afford after drying in vacuo 108 mg of a light yellow powder (0.16 mmol, 69 %). ¹H NMR (300 MHz, C₆H₆) δ (ppm) 10.96 (s, 1 H, CHCMe₂Ph), 7.33 (m, 2H, Ph), 7.20-6.87 (m, 6H, Ph-ArcFs), 6.75 (m, 1 H, Ph), 6.52 (t, 1 H, Ar_CF3, J = 8.0 Hz), 6.02 (br s, 6H, Me₂PyA^"), 2.11 (br s, 12H, Me₂Pyr), 1.58 (s, 6H, CHCMe₂Ph). ¹⁹F NMR (200 MHz, C₆D₆) δ (ppm) -60.4 (s, 3F, CF₃). 2.2 Synthesis of supported catalysts according to the invention

Example 1 : Synthesis of [(≡SiO)W(NAr)(CHCMe₃)(OtBu)] (Ar = 2_>6-iPr₂C₆H₃), (Representative procedure):

A solution of 104 mg of [W(NAr)(CHCMe₃)(OtBu)₂] (0.181 mmol, 1 .05 equiv.) in benzene (2 ml_) was added to a suspension of SiO_2-(700) (673 mg, 0,17 mmol) in benzene (2 mL) at room temperature. The suspension was slowly stirred at room temperature for 12h, resulting in a fading of the color of the solution and a coloration of the silica to yellow. The yellow solid was collected by filtration, and was washed by four suspen- sion/filtration cycles in benzene (4 x 2 mL). The resulting yellow solid was dried thoroughly under high vacuum (10^~5 mBar) at room temperature for 3h to afford 672 mg of the title compound. All the filtrate solutions were collected and analyzed by H NMR spectroscopy in C₆D₆ using ferrocene as internal standard (33.7 mg, 1.05 equiv.), indicating that 0.07 mmol of tBuOH were released upon grafting (0.4 tBuOH/W_surf). Ele- mental Analysis: W 3.32%, C 4,78%, H 0.68%, N 0.48% corresponding to 22 C/W (21 expected), 37.4 H/W (36 expected), 1.9 N (1 expected).

Example 2: [(≡SiO)W(NAr)(CHCMe₃)(OtBu_F3)] (Ar = 2,6-iPr₂C₆H₃₎ tBu_F3OH = (CF₃)Me₂COH)

From a solution of [W(NAr)(CHCMe₃)(OtBu_F3)2(DME)] and a suspension of SiO_2-(700) (500 mg, 0.13 mmol) in benzene (2 mL) 552 mg of a yellow solid were isolated. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as internal standard (11 mg, 1 equiv.), indicating that 0.1 1 mmol of tBu_F3OH were released upon grafting (0.85 tBu_F3OH/W_surf). Elemental Analysis: W 3.71 %, C 5.18%, H 0.72%, N 0.38% F 1.09% corresponding to 21.4 C/W (21 expected), 35.4 H/W (33 expected), 1 ,3 N (1 expected).

Example 3: [(≡SiO)W(NAr)(CHCMe₃)(OtBu_F6)] (Ar = 2,6-iPr₂C₆H₃, tBu_F6OH = (CF₃)₂MeCOH)

From a solution of 100 mg of [W(NAr)(CHCMe₃)(OtBu_F6)₂] (0,13 mmol, 1 ,05 equiv.) in benzene (3 mL) and a suspension of Si0₂-(₇₀o) (500 mg, 0,12 mmol) in benzene (2 mL), 512 mg of a light orange solid were isolated. All the filtrate solutions were collected and analyzed by H NMR spectroscopy in C₆D₆ using ferrocene as internal stand- ard (1 1 .8 mg, 0.5 equiv.), indicating that 0,10 mmol of tBu_F60H were released upon grafting (0,8 tBu_F6OH/W_surf). Elemental Analysis: W 3.88%, C 5.39%, H 0.65%, N 0,37%, F 2.05% corresponding to 21 .3 C/W (21 expected), 30.6 H/W (30 expected), 1 ,3 N (1 expected).

Example 4: [(=SiO)W(NAr)(CHCMe₃)(OtBu_F9)] (Ar = 2,6-iPr₂C₆H₃, tBu_F9OH = (CF₃)₃COH)

From a solution of 185.9 mg of [W(NAr)(CHCMe₃)(OtBu_F9)₂] (0,21 mmol, 1 ,05 equiv.) in benzene (4 ml_) and a suspension of Si0_2-(7oo) (790 mg, 0,12 mmol) in benzene (3 mL) 857 mg of an orange solid were isolated. Elemental Analysis: W 3.47%, C 4.84%, H 0.51 %, N 0.38%, F 3.14% corresponding to 21.3 C W (21 expected), 26.8 H/W (27 expected), 1.4 N (1 expected).

Example 5: [(=SiO)W(NAr_Ci)(CHCMe₂Ph)(Me₂Pyr)] (Ar_Ci = 2,6-CI-C₆H₃, e₂Pyr = 2,5-dimethylpyrrolide)

From a solution of 138 mg of [W(NAr_Ci)(CHCMe₂Ph)(Me₂Pyr)₂] (0,21 mmol, 1 ,05 equiv.) in benzene (3 mL) and a suspension of Si0_2-(7oo) (800 mg, 0,20 mmol) in benzene (2 mL) 790 mg of a light brown solid were isolated. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as internal standard (38.7 mg, 1 equiv.), indicating that 0.13 mmol of Me₂PyrH were released upon grafting (0.7 Me₂PyrH/W_surf).

Example 6: [(=SiO)W(NArci)(CHCMe₂Ph)(OtBu_F6)], (Ar_C) = 2,6-CI-C₆H₃, tBu_F6OH = (CF₃)₂MeCOH))

From a solution of 101 mg of [W(NAr_Ci)(CHCMe₃)(OtBu_F6)₂] (0,13 mmol, 1 ,05 equiv.) in benzene (2 mL) and a suspension of SiO_2-(700) (463 mg, 0,12 mmol) in benzene (2 mL), 450 mg of a light orange solid were isolated. All the filtrate solutions were collected and analysed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as internal standard (22.3 mg, 1 equiv.), indicating that 0.08 mmol of tBu_F6OH were released upon grafting (0.7 tBu_F6OH/W_Surf). Example 7: [(≡SiO)W(NAr_Ci)(CHCMe₂Ph)(OtBu_F9)], (Ar = 2,6-CI-C₆H_3> tBu_F9OH = (CF₃)₃COH))

From a solution of 98.5 mg of [W(NArci)(CHCMe₂Ph)(OtBu_F9)2(D E)] (0,10 mmol, 1 ,05 equiv.) in benzene (2 mL) and a suspension of Si0_2-(7oo) (365 mg, 0,09 mmol) in ben- zene (2 mL) 360 mg of a light orange solid were obtained. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as internal standard (17.7 mg, 1 equiv.), indicating that 0.09 mmol of DME were released upon grafting (0.9 DME/W_surf). Example 8: [(≡SiO)W(NAr_CF3)(CHCMe₂Ph)(Me₂Pyr)] (Ar_CF3 = 2-CF₃-C₆H₄, Me₂Pyr = 2,5-dimethylpyrrolide)

From a solution of 75 mg of [W(NArcF3)(CHCMe₂Ph)(Me₂Pyr)₂] (0,1 1 mmol, 1 ,05 equiv.) in benzene (3 mL) and a suspension of Si0_2-(70o) (403 mg, 0, 10 mmol) in benzene (2 mL), 390 mg of a yellow solid were isolated. All the filtrate solutions were col- lected and analyzed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as internal standard (38.7 mg, 1 equiv.), indicating that 0.09 mmol of Me₂PyrH were released upon grafting (0.95 Me₂PyrH/W_surf).

Example 9: [(=SiO)W(NAr_Ci)(CHCMe₂Ph)(OtBu)] (Ar_Ci = 2,6-CI-C₆H₃₎

A solution of 100 mg of [W(NAr_Ci)(CHCMe₂Ph)(OtBu)₂] (0,16 mmol, 1 .05 equiv.) in cold toluene (2 mL, -40 °C) was added to a suspension of Si0_2-(70o) (576 mg, 0.15 mmol) in cold toluene (2 mL, -40 °C). The suspension was slowly stirred at room temperature for 30 min, resulting in a fading of the color of the solution and a coloration of the silica to orange. The orange solid was collected by filtration, and was washed by four sus- pension/filtration cycles in benzene (4 x 2 mL). The resulting orange solid was dried thoroughly under high vacuum (10^~5 mBar) at room temperature for 5h to afford 1 10 mg of the title compound. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as internal standard (27.9 mg, 1 equiv.), indicating that 0.12 mmol of tBuOH were released upon grafting (0.8 tBuOH/W_surf).

Example 10: [(=SiO)W(NAr)(CHCMe₃)(SAr')] (Ar = 2,6-iPr₂C₆H_3; Ar'= 2,4,6-iPr₃C₆H₃)

From a solution of 59 mg of [W(NAr)(CHCMe₃)(SAr')₂] (0,07 mmol, 1 ,05 equiv.) in benzene (2 mL) and a suspension of Si0_2-(70o) (230 mg, 0,06 mmol) in benzene (1 mL), 150 mg of a yellow solid were isolated. All the filtrate solutions were collected and analyzed by ¹ H NMR spectroscopy in C₆D₆ using ferrocene as internal standard (1 1 .5 mg, 1 equiv.), indicating that 0.05 mmol of ArS'H were released upon grafting (0.85 Ar'SH/W_surf).

Example 11 : [(≡SiO)W(NAr)(CHCMe₂Ph)(OSiPh₃)] (Ar = 2,6-iPr₂C₆H₃)

From a solution of 241 mg of [W(NAr)(CHCMe₂Ph)(OSiPh)₂] (0,21 mmol, 1 ,05 equiv.) in benzene (4 ml_) and a suspension of Si0₂-(7oo) (810 mg, 0,23 mmol) in benzene (2 ml_), a light orange solid were isolated. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as internal standard (52.3 mg, 1.33 equiv.), indicating that 0.48 mmol of HOSiPh₃ were released upon grafting.

Example 12: [(=SiO)W(NAr_F5)(CHCMe₂Ph)(Me₂Pyr)] (Ar_F5 = C₆F₅)

From a solution of 59 mg of [W(NC₆F₅)(CHCMe₂Ph)(Me2Pyr)2] (0.086 mmol, 1.05 equiv.) in benzene (3 mL) and a suspension of SiO_2-(700) (314 mg, 0.082 mmol) in benzene (3 mL), 343 mg of a orange-yellow solid were isolated. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as an internal standard, indicating that 0.07 mmol of Me₂PyrH were released upon grafting (0.9 Me₂PyrH/W_SUrf). Elemental Analysis: W 4.13%, C 5.95%, H 0.48%, N 0.77% F 2.17% corresponding to 22.1 C/W (22 expected), 21.2 H/W (20 expected), 2.4 N (2 expected), 5.1 F (5 expected).

Example 13: [(≡SiO)W(NAr)(CHCMe₂Ph)(OAr_F5)] (Ar = 2,6-iPr₂C₆H₃) Example 14: Synthesis of [(=SiO)W(NAr_CF3)(CHCMe₂Ph)(OtBu_F6)] (Ar_CF3 =

2-CF₃C₆H₄, tBu_F60 = CH₃C(CF₃)₂0)

From a solution of [W(NAr_CF3)(CHCMe₂Ph)(OtBu_F6)₂] (70 mg, 0.084 mmol, 1.05 equiv.) and a suspension of Si0_2-(7oo) (306 mg, 0.080 mmol) in benzene (2 mL) 325 mg of a yellow solid were isolated. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as an internal standard, indicating that 0.066 mmol of tBu_F6OH were released upon grafting (0.8 tBu_F60H/W_SUrf). Elemental Analysis: W 3.90%, C 5.56%, H 0.49%, N 0.27% F 3.70% corresponding to 21.8 C/W (21 expected), 22.9 H/W (19 expected), 0.9 N (1 expected), 9.2 F (9 expected). Example 15: Synthesis of [(≡SiO)W(NAr)(CHCMe₃)(OSi(OtBu)₃)] (Ar = 2,6- iPr₂C₆H₃)

From a solution of 130 mg of [W(NAr)(CHCMe₃)(OSi(OtBu)₃)2] (0.136 mmol, 1.05 equiv.) in benzene (3 ml_) and a suspension of Si0₂-(7oo) (500 mg, 0.129 mmol) in benzene (3 ml_), 558 mg of a light orange solid was isolated. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as internal standard (24 mg, 1.05 equiv.), indicating that 0.06 mmol of (tBuO)₃SiOH were released upon grafting (0.54 (tBuO)₃SiOH/W_surf). Elemental Analysis: W 2.48 %, C 4.72 %, H 0.76 %, N 0.29 % corresponding to 29.1 C/W (29 expected), 55.9 H W (54 expected), 1 .5 N (1 expected).

Example 16: Synthesis of [(≡SiO)W(NAr_Ci)(CHCMe₂Ph)(OSi(OtBu)₃)] (Ar_Ci = 2,6- ΟΙ₂θ₆Η₃)

From a solution of 54 mg of [W(NAr_Ci)(CHCMe₂Ph)(OSi(OtBu)₃)₂] (0.054 mmol, 1.05 equiv.) in benzene (3 ml_) and a suspension of Si0_2-(7oo) (197 mg, 0.051 mmol) in benzene (2 mL) 202 mg of a orange-yellow solid were isolated. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as an internal standard, indicating that 0.03 mmol of HOSi(OtBu)₃ were released upon grafting (0.6 HOSi(OtBu)₃/W_surf). Elemental Analysis: W 2.72 %, C 5.29 %, H 0.72 %, N 0.38 % F 0.91 % corresponding to 29.8 C/W (29 expected), 48.3 H/W (43 expected), 1.8 N (1 expected), 3.2 F (3 expected).

Example 17: Synthesis of [(=SiO)W(NAr_F5)(CHCMe₂Ph)(OtBuF6)] (Ar_F5 = C₆F₅)

From a solution of 35.2 mg of [W(NC₆F5)(CHCMe₂Ph)(OtBu_F6)2] (0.040 mmol, 1.05 equiv.) in cold toluene (2 mL, -40 °C) and a suspension of Si0_2-(7oo) (150 mg, 0.039 mmol) in cold toluene (2 mL, -40 °C). The suspension was slowly stirred at room temperature for 30 min, resulting in a fading of the color of the solution and a coloration of the silica to orange. The orange solid was collected by filtration, and was washed by four suspension/filtration cycles in benzene (4 x 2 mL). The resulting or- ange solid was dried thoroughly under high vacuum (10^~5 mBar) at room temperature for 5h to afford 167 mg of a orange-yellow solid. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using ferrocene as an internal standard, indicating that 0.023 mmol of Me₂PyrH were released upon grafting (0.7 tBu_F6OH/W_surf). Elemental Analysis: W 3.08%, C 3.94%, H 0.29%, N 0.27% F 3.51 % corresponding to 19.6 C/W (20 expected), 17.2 H/W (15 expected), 1.2 N (1 expected), 1 1.0 F (11 expected). Example 18: Synthesis of [(≡SiO)W(NAr_F5)(CHCMe₂Ph)(OtBu_F9)(DME)] (Ar_F5 = C₆F₅)

From a solution of 52.5 mg of [W(NC₆F5)(CHCMe₂Ph)(OtBu_F9)2(DME)] (0.049 mmol, 1.05 equiv.) in cold toluene (3 ml_) and a suspension of Si0_2-(7oo) (182 mg, 0.047 mmol) in cold toluene. The suspension was slowly stirred at room temperature for 30 min, resulting in a fading of the color of the solution and a coloration of the silica to orange. The orange solid was collected by filtration, and was washed by four suspension/filtration cycles in benzene (4 ^χ 2 ml_). The resulting orange solid was dried thoroughly under high vacuum (10^~5 mBar) at room temperature for 5h to afford 187 mg of a orange-yellow solid were isolated. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using C₆H₅F as internal standard, indicating that 0.040 mmol of tBu_F9OH were released upon grafting (0.86 tBu gOH/W_surf) Elemental Analysis: W 3.46%, C 5.08%, H 0.38%, N 0.37% F 4.69% corresponding to 22.5 C/W (24 expected), 20 H/W (22 expected), 1.4 N (1 expected), 13.1 F (14 expected).

Example 19: Synthesis of [(≡SiO)W(NArc_F3)(CHCMe₂Ph)(OtBu_F9)] (Ar_CF3 = 2-CF₃C₆H₄, tBu_FgOH = (CF₃)₃COH)

From a solution of [W(NAr_CF3)(CHCMe₂Ph)(OtBu_F9)₂] (79 mg, 0.083 mmol, 1.05 equiv.) and a suspension of Si0_2-(7oo) (302 mg, 0.079 mmol) in benzene (2 ml_) 333 mg of a orange solid were isolated. All the filtrate solutions were collected and analyzed by ¹H NMR spectroscopy in C₆D₆ using C₆H₅F as internal standard, indicating that 0.076 mmol of tBupgOH were released upon grafting (0.95 tBu_F9OH/W_surf). Elemental Analysis: W 3.62%, C 5.34%, H 0.46%, N 0.40% F 5.39% corresponding to 22.6 C/W (21 expected), 23.2 H/W (16 expected), 1.5 N (1 expected), 14.4 F (12 expected).

Comparison: [(≡SiO)W(NAr)(CHCMe₃)(Me₂Pyr)] (Ar = 2,6-iPr₂C₆H₃) 3. Catalytic activity

Metathesis of cis-non-4-ene:

At t=0, a 0.8 M solution of cis-non-4-ene in toluene containing heptane as internal standard (0.08 M) was added to the catalyst introduced in a conical base vial containing a wing shaped stirring bar. The reaction mixture was stirred at 600 rpm and kept at 30°C using an aluminum heating block. 10 μΙ_ aliquots of the solution were sampled, diluted with pure toluene (100 μΙ_) and quenched by the addition of 1 μΙ_ of ethyl acetate. The resulting solution was analyzed by GC/FID (Agilent Technologies 7890 A) equipped with an HP-5 (Agilent Technologies) column.

Results are summarized in the following table:

TOF_3mjn Time to final conver¬

Catalyst (0.1 mol % W) from Example

(min ¹) sion

1 : [(=SiO)W(NAr)(CHCMe₃)(OtBu)] 5 < 8 h

2: [(≡SiO)W(NAr)(CHCMe₃)(OtBu_F3)] 16 2 h 40

3: [(≡SiO)W(NAr)(CHCMe₃)(OtBu_F6)] 75 < 30 min

4: [(=SiO)W(NAr)(CHCMe₃)(OtBu_F9)] 1 15 < 10 min

10: [(≡SiO)W(NAr)(CHCMe₃)(SAr')] 5 6 h

11 : [(≡SiO)W(NAr)(CHCMe₃)(OSiPh₃)] 3 a)

Comparison:

9 4 h

[(=SiO)W(NAr)(CHCMe₃)(Me₂Pyr)]

9: [(≡SiO)W(NAr_Ci)(CHCMe₂Ph)(OtBu)] 40 30 min

5: [(≡SiO)W(NAr_Ci)(CHCMe₂Ph)(Me₂Pyr)] 40 30 min

6: [(≡SiO)W(NAr_Ci)(CHCMe₂Ph)(OtBu_F6)] 98 < 20 min

7: [(=SiO)W(NAr_Ci)(CHCMe₂Ph)(OtBu_F9)] 35 40 min 8: [(≡SiO)W(NArc_F3)(CHCMe₂Ph)(Me₂Pyr)] 79 20 min

12: [(≡SiO)W(NAr_F5)(CHCMe₂Ph)(Me₂Py r)] 96 < 20 min

14: [(≡SiO)W(NAr_CF3)(CHCMe₂Ph)(OtBu_F6] 51 45 min

15: [(≡SiO)W(NAr)(CHCMe₃)(OSi(OtBu)₃)] 41 < 30 min

16: [(≡SiO)W(NAr_Ci)(CHCMe₂Ph)(OSi(OtBu)₃)] 39 < 3h

17: [(≡SiO)W(NAr_F5)(CHCMe₂Ph)(OtBu_F6)] 38 30 min

18: [(=SiO)W(NAr_F5)(CHCMe₂Ph)(OtBu_F9] (in

25 < 1 h

form of a complex with DME)

19: [(≡SiO)W(NAr_CF3)(CHCMe₂Ph)(OtBu_F9)] 34 1 h

a) full conversion was not reached; equilibrium at 14 % conversion after 24 h

4. Catalyst recycling

Step a: A 0.5 M solution of cis-non-4-ene in toluene containing heptane as internal standard (0.1 M) was added to the catalyst 4 (catalyst to substrate ratio 1000) in a conical base vial containing a wing shaped magnetic stirred.

Step b: The reaction mixture was stirred at 600 rpm and kept at 30°C using an aluminum heating block for 20 min. After leaving the supported catalyst settling, the olefin mixture was filtered out, and replaced by the same amount of fresh cis-non-4-ene solution, keeping the catalyst to substrate ratio to 1000.

Step b was repeated five times without any loss of activity of the catalyst (equilibrium conversion of the substrate reached each time).

Claims

Claims

Compound of formula I

R¹

I

wherein

M is W;

R¹ is H, aryl, heteroaryl, alkyi, or heteroalkyi, optionally substituted, respectively;

R² and R³ can be the same or different and are hydrogen, alkyi, alkenyl, heteroalkyi, heteroalkenyl, aryl, or heteroaryl, optionally substituted, respectively;

R⁵ is a residue R⁶-X-, wherein

R⁶ is alkyi, aryl, heteroalkyi, heteroaryl, optionally substituted, respectively;

(R⁷, R⁸, R⁹)Si, wherein R⁷, R⁸, R⁹ are independently alkyi, alkoxy, phenyl or phe- noxy, optionally substituted, respectively; (R¹⁰, R¹¹, R¹²)C, wherein R¹⁰, R¹¹, R¹² are independently phenyl, alkyi, optionally substituted, respectively;

X = O, S, or NR¹³, wherein R¹³ is H; or alkyi or aryl, optionally substituted, respectively; or

R⁵ is R⁶-CO-NR¹³, wherein R⁶ and NR¹³ have the meaning as defined above, or wherein R⁶ and R¹³ taken together form a carbon chain having from 2 to 6 carbon atoms; or

R⁵ is a 4 to 8 membered N-containing ring, preferably a N-containing carbon ring, wherein N is linked to M; and R⁴ is a residue 0-Si(0-)₃, and represents silica to which M is linked forming a M-O- Si(0-)₃ moiety, preferably wherein silica is comprised in a solid support; under the proviso that a compound in which

R¹ = 2,6-diisopropylphenyl,

R⁵ = 2,5-dimethylpyrrol-1-yl,

R² = tBu, and

R³ = H is excluded.

Compound of claim 1 , wherein

R¹ is aryl or adamant-1-yl, optionally substituted, respectively; preferably wherein aryl is phenyl or naphthyl, or phenyl or naphthyl substituted with up to five substituents independently selected from C C₄ alkyi, C C₄ alkoxy, CF₃, F, CI, Br; or phenyl or phenoxy, optionally substituted, respectively;

R² is -C(CH₃)₂C₆H₅ or -C(CH₃)₃;

R³ is H;

R⁵ is a residue R⁶-X-, wherein

X = O and R⁶ is phenyl or phenyl substituted with up to five substituents independently selected from alkyi, preferably Ci-C₄ alkyi, such as methyl, isopropyl or t-butyl; alkoxy, preferably C₁-C4 alkoxy; phenoxy, phenyl, optionally substituted, respectively; or halogen; or

X = S and R⁶ is phenyl or phenyl substituted with up to five substituents independently selected from alkyi, preferably ^-ΰ₄ alkyi such as methyl, isopropyl or t-butyl; alkoxy, preferably C C alkoxy; phenoxy, phenyl, optionally substituted, respectively; or halogen; or

X = O and R⁶ is triphenylsilyl or triphenoxysilyl, optionally substituted, respectively; or tri(C-i-C₄ alkyl)silyl or tri(C-i-C₄ alkoxy)silyl; or

X = O and R⁶ is triphenylmethyl, optionally substituted; or

X = O and R⁶ is 9-phenyl-fluorene-9-yl; or X = O and R⁶ is (C₆H₅)(CF₃)2C; or

X = O and R⁶ is t-butyl, optionally substituted with one or more F groups, preferably (CF₃)(CH₃)₂C, (CF₃)₂(CH₃)C, (CF₃)₃C.

Compound of claim 1 or 2, wherein

R¹ is phenyl substituted with up to five substituents independently selected from C_r

C₄ alkyl, C C₄ alkoxy, CF₃, F, CI, Br; or phenyl or phenoxy, optionally substituted, respectively; and

R⁵ is a residue R⁶-X-, wherein

X = O and R⁶ is phenyl or phenyl substituted with up to five substituents independently selected from C C₄ alkyl, C C alkoxy, phenoxy, phenyl, halogen; or X = S and R⁶ is phenyl or phenyl substituted with up to five substituents independently selected from C C alkyl, C1-C4 alkoxy, phenoxy, phenyl, halogen; or X = O and R⁶ is triphenylsilyl, triphenoxysilyl, tri(C₁-C₄ alkyl)silyl or tri(C₁-C₄ alkoxy)silyl; or

X = O and R⁶ is t-butyl or t-butyl substituted with one or more F groups; or

R⁵ is pyrrol-1-yl, 2,5-dimethylpyrrol-1-yl, or 2,5-diphenylpyrrol-1-yl.

Compound of any one of the preceding claims, wherein R¹ is an electron donating group and R⁵ is an electron withdrawing group.

Compound of any one of the preceding claims, wherein

R¹ = phenyl substituted with up to five substituents independently selected from C-r

C alkyl, C C₄ alkoxy, phenyl, phenoxy, preferably wherein R¹ is 2,6- diisopropylphenyl;

R² is -C(CH₃)₂C₆H₅ or -C(CH₃)₃;

R³ is H;

R⁵ is (CF₃)(CH₃)₂CO, (CF₃)₂(CH₃)CO, (CF₃)₃CO, (C₆H₅)(CF₃)₂CO, pyrrol-1-yl, 2,5- dimethylpyrrol-1 -yl, or 2,5-diphenylpyrrol-1-yl.

Compound of any one of claims 1 to 3, wherein R¹ is an electron withdrawing group and R⁵ is an electron donating group.

7. Compound of any one of claims 1 to 3 or 6, wherein

R¹ is phenyl substituted with up to five substituents independently selected from CF₃, F, CI, Br, preferably wherein R¹ is 2,6-dichlorophenyl, pentafluorophenyl, 2- (trifluoromethyl)phenyl or 2,6-di(trifluoromethyl)phenyl;

R² is -C(CH₃)₂C₆H₅ or -C(CH₃)₃;

R³ is H;

R⁵ is (CH₃)₃CO, tri(C -C alkyl)silyloxy, tri(C₁-C₄alkoxy)silyloxy, tri(phenyl)silyloxy, or tri(phenoxy)silyloxy, or phenoxy or phenylthio, wherein the phenyl moiety may be substituted with up to five substituents independently selected from C C₄ alkyl, C C₄ alkoxy, phenoxy, phenyl, halogen.

8. Compound of any one of claims 1 to 3, wherein both R¹ and R⁵ are electron withdrawing groups. 9. Compound of any one of claims 1 to 3 or 8, wherein

R¹ is phenyl substituted with up to five substituents independently selected from CF₃,

F, CI, Br, preferably wherein R¹ is 2,6-dichlorophenyl, pentafluorophenyl, 2-

(trifluoromethyl)phenyl or 2,6-di(trifluoromethyl)phenyl;

R² is -C(CH₃)₂C₆H₅ or -C(CH₃)₃;

R³ is H;

R⁵ is (CF₃)(CH₃)₂CO, (CF₃)₂(CH₃)CO, (CF₃)₃CO, (C₆H₅)(CF₃)₂CO, pyrrol-1-yl, 2,5- dimethylpyrrol-1 -yl, 2,5-diphenylpyrrol-1 -yl.

10. Compound of any one of the preceding claims, wherein R¹, R², R³ and R⁵ are selected such that the compound of formula I exhibits in a metathesis reaction a turn over frequency that is higher than the turnover frequency that is achieved under the same reaction conditions with a compound of formula I in which R¹ = 2,6-diisopropylphenyl, R⁵ = 2,5-dimethylpyrrol-1-yl, R² = tBu and R³ = H, preferably wherein cis-4-nonene is subjected to self-metathesis, preferably wherein R¹, R², R³ and R⁵ are defined in any one of claims 5, 7 or 9. Method of forming an olefin from a first olefin and a second olefin in a metathesis reaction, comprising step (i):

(i) reacting the first olefin with the second olefin in the presence of a compound as defined in any one of the preceding claims, preferably claim 10; preferably wherein

(a) the first olefin has a terminal olefinic double bond, and the second olefin has a terminal olefinic double bond, wherein the first and the second olefin are identical [homo or self-metathesis (SM)]; or

(b) the first and the second olefin are different from one another [cross metathesis (CM)]; or

(c) the first olefin has an internal olefinic double bond and the second olefin is ethylene [ethenolysis]; or

(d) the first olefin is a cyclic olefin and the second olefin is a cyclic olefin, wherein the first and the second olefin may be identical or may be different from one another [cross metathesis (CM)]; or

(e) the first olefin is a diene and the second olefin is a diene, wherein the first olefin and the second olefin are identical, wherein step (i) results in ring closing of the diene [ring closing metathesis (RCM)]; or

(f) the first olefin is a cyclic olefin and the second olefin is a cyclic olefin, wherein the first olefin and the second olefin are identical, wherein step (i) results in a ring opening metathesis polymerization (ROMP); or

(g) the first olefin is a terminal diene and the second olefin is a terminal diene, wherein the first olefin and the second olefin are identical, and wherein step (i) results in an acyclic diene metathesis polymerization (ADMET), wherein a polyene and ethylene are generated.

Method according to claim 11 , further comprising at least step (ii) or steps (ii) and (ii) separating off the compound from the reaction mixture obtained in step (i), preferably by filtration or centrifugation or distilling off the reaction mixture from the compound;

(iii) re-using in step (i) the catalyst obtained in step (ii).

13. Addition product of the compound as defined in any one of claims 1 to 10 with the first or the second olefin as defined in claim 1 1 , wherein the addition product is

(a) a product in which the first or the second olefin as defined in claim 1 1 forms via its olefinic double bond together with the compound as defined in any one of claims 1 to 10 a metallacyclobutane moiety, and R² and R³ are attached to the metallacyclobutane ring.

14. Use of a compound as defined in any one of claims 1 to 10 or 13 in a metathesis reaction, preferably wherein the metathesis reaction is selected from the group consisting of cross metathesis (CM), homo or self-metathesis (SM), ring opening metathesis (ROM), ring closing metathesis (RCM), ring opening metathesis polymerization (ROMP), ethenolysis, or acyclic diene metathesis polymerization (ADMET). 15. Compound of any one of claims 1 to 10, wherein the compound of formula I is of formula

1 : [(≡SiO)W(NAr)(CHCMe₃)(OtBu)]

2: [(≡SiO)W(NAr)(CHCMe₃)(OtBu_F3)]

3: [(≡SiO)W(NAr)(CHCMe₃)(OtBu_F6)]

4: [(≡SiO)W(NAr)(CHCMe₃)(OtBu_F9)]

5: [(≡SiO)W(NAr_Ci)(CHCMe₂Ph)(Me₂Pyr)]

6: [(≡SiO)W(NArci)(CHCMe₂Ph)(OtBu_F6)]

7: [(≡SiO)W(NArci)(CHCMe₂Ph)(OtBu_F9)]

8: [(≡SiO)W(NArc_F3)(CHCMe₂Ph)(Me₂Pyr)]

9: [(≡SiO)W(NAr_Ci)(CHCMe₂Ph)(OtBu)]

10: [(≡SiO)W(NAr)(CHCMe₃)(SAr')]

11 : [(≡SiO)W(NAr)(CHCMe₃)(OSiPh₃)] 12: [(≡SiO)W(NAr_F5)(CHCMe₂Ph)(Me₂Pyr)]

13: [(≡SiO)W(NAr)(CHCMe₂Ph)(OAr_F5)].

14: [(≡SiO)W(NAr_CF3)(CHCMe₂Ph)(OtBu_F6]

15: [(≡SiO)W(NAr)(CHCMe₃)(OSi(OtBu)₃)]

16: [(≡SiO)W(NAr_Ci)(CHCMe₂Ph)(OSi(OtBu)₃)]

17: [(≡SiO)W(NAr_F5)(CHCMe₂Ph)(OtBu_F6)]

18: [(≡SiO)W(NAr_F5)(CHCMe₂Ph)(OtBu_F9)(DME)]

19: [(≡SiO)W(NAr_CF3)(CHCMe₂Ph)(OtBu_F9)]

(Ar = 2,6-diisopropylphenyl; Ar_a = 2,6-dichlorophenyl, Ar_CF3 = 2- trifluoromethylphenyl, Ar_F5 = C₆F₅, Me = CH₃, tBu = (CH₃)₃C, tBu_F3 = (CF₃)(CH₃)₂C, tBu_F6 = (CF₃)₂(CH₃)C, tBu_F9 = (CF₃)₃C, Ph = C₆H₅, Ar' = 2,4,6-triisopropylphenyl, Me₂Pyr = 2,5-dimethylpyrrol-1-yl). or a compound

[W(NAr)(CHCMe₃)(OtBu_F9)₂] which is the starting material for compound of formula I-4; or

[W(NAr_Ci)(CHCMe₂Ph)(OtBu_F9)₂(DME)] which is the starting material for compound of formula I-7; or

[W(NAr_Ci)(CHCMe₂Ph)(OtBu)₂] which is the starting material for compound of formula I-9; or

W(NAr_CF3)₂CI₂(DME),

W(NAr_CF3)(CHCMe₂Ph)(OTf)₂(DME) and W(NAr_CF3)(CHCMe₂Ph)(Me2Pyr)₂ which are starting materials for the compound of formula I-8; or

W(NAr_F5)(CHMe₂Ph)(Me₂Pyr)₂ as starting material for the compound of formula 1-12; or W(NAr_F5)(CHMe₂Ph)(OTf)₂ (optionally as complex with DME) as a starting material for compounds of formula 1-17 and 1-18;

(DME = 1 ,2-dimethoxyethane; TfO = trifluoromethanesulfonate).