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The heteroelement-containing alkylidene imide complexes with molybdenum and tungsten Et3SiCH=Mo(NAr)(OR)2 (I), Et3 ECH=W(NAr)(OR)2 (E = Si (II), Ge (III); Ar = 2,6-i-Pr2C6H3; R=CMe2 CF3) and π-complex (RO)2(ArN)Mo(CH2=CH-GeEt3) (IV) were synthesized by the reaction of Alkyl-CH=M(NAr) (OR)2 (M=Mo, W; Alkyl = t-Bu, PhMe2C) with organosilicon and organogermanium vinyl reagents Et3ECH=CH2 (E = Si, Ge). The structure of compounds I–III was determined by X-ray diffraction (XRD). The complexes I–IV are active initiators of metathesis polymerization of cycloolefins.

Bimetallic alkylidene complexes of tungsten (R′O)2(ArN)W CH–SiR2–CH W(NAr)(OR′)2 (R = Me (1), Ph (2)) and (R′O)2(ArN)W CH–SiMe2SiMe2–CH W(NAr)(OR′)2 (3) (Ar = 2 , 6 – Pr 2 i C 6 H 3 ; R′ = CMe2CF3) have been prepared by the reactions of divinyl silicon reagents R2Si(CH CH2)2 with known alkylidene compounds R′′–CH Mo(NAr)(OR′)2. (R′′ = But, PhMe2C) Complexes 1–3 were structurally characterized. Ring opening metathesis polymerization (ROMP) of cyclooctene using compounds 1–3 as initiators led to the formation of high molecular weight polyoctenamers with predominant trans-units content in the case of 1 and 3 and predominant cis-units content in the case of 2.

Catalytic properties of the silicon-containing carbene complexes of tungsten Me3Si-CH=W(NAr)(OR′)2(1) and PhMe2Si-CH=W(NAr)(OR′)2 (2) and their hydrocarbon analogs Me3C-CH=W(NAr)(OR′)2 (3) and PhMe2C-CH=W(NAr)(OR′)2 (4) (Ar = 2,6-Pri 2C6H3, R′ = CMe2CF3) were studied in homometathesis of hex-1-ene, metathesis polycondensation of deca-1,9-diene, and ring opening metathesis polymerization of cyclooctene. The nature of the carbene fragment in the tungsten catalysts substantially affects their catalytic activity. Silicon-containing catalysts 1 and 2 were found to be 3−5 times less active than their hydrocarbon analogs 3 and 4. Metathesis polymerization of cyclooctene in the bulk with initiators 1–4 completed within a few minutes to form a block. Stereoregularity of the formed polyoctenamers depends to a considerable extent on the nature of the carbene fragments in the starting initiators. Initiators 1–2 lead to polyoctenamers mainly containing the cis-units, whereas the use of complexes 3 and 4 affords polyoctenamers mainly containing the trans-units. The structures of novel compound 2 and known complexes 1, 3, and 4 were determined by X-ray diffraction analysis.

Alkylidene complex of tungsten Me3Ge-CH W(NAr)(OCMe2CF3)2 (1) ( Ar = 2 , 6 - Pr 2 i C 6 H 3 ) has been prepared by the reaction of Me3GeCH CH2 with known alkylidene compound But–CH Mo(NAr)(OCMe2CF3)2 at a molar ratio 1:1. Metallacycle [CH(GeMe3)CH(GeMe3)CH2]W(NAr)(OCMe2CF3)2 (2) was isolated from the same reaction when twofold excess of Me3GeCH CH2 was used. The both compounds 1 and 2 were structurally characterized. They were found to have low activity in metathesis of 1-hexene and high activity in ROMP of cyclooctene and norbornene.

The novel silicon-, germanium- and tin-containing imido alkyl complexes of tungsten of the type (ArN)2W(CH2EMe3)2 ( Ar = 2 , 6 - Pr 2 i C 6 H 3 ; E = Si (1), Ge (2), Sn (3)) have been prepared by the reactions of (ArN)2WCl2(dme) (dme = 1,2-dimethoxyethane) with heteroelement-containing alkyllithium or Grignard reagents Me3ECH2Li (E = Si, Ge), Me3ECH2MgCl (E = Ge, Sn). The title compounds were isolated in high yields as crystalline solids and characterized by elemental analysis, IR, 1H, 13C, 29Si and 119Sn NMR spectroscopy and X-ray diffraction studies. The geometry of the W atoms in the compounds can be described as a distorted tetrahedron.

Alkylidene complex of molybdenum Ph3Si–CH Mo(NAr)(OCMe2CF3)2 (1) ( Ar = 2 , 6 - Pr 2 i C 6 H 3 ) has been prepared by the reaction of Ph3SiCH CH2 with known alkylidene compounds Alkyl-CH Mo(NAr)(OCMe2CF3)2 (Alkyl = But, PhMe2C). According to X-ray diffraction studies the geometry of the Mo atom in (1) can be described as a distorted tetrahedron. Reactions of heteroelement-containing imido alkyl compounds of molybdenum and tungsten (ArN)2M(CH2EMe3)2 ( Ar = 2 , 6 - Pr 2 i C 6 H 3 ; M = Mo. W; E = Si, Ge, Sn) with triflic acid were shown to yield a complex mixture of products among which carbene complexes have not been observed. The formation of carbene complexes of tungsten in low yields was observed by 1H NMR spectroscopy in the reactions of (ArN)2W(CH2EMe3)2 (E = Si, Ge, Sn) with hydrogen chloride in THF-d8. Catalytic properties of heteroelement-containing alkylidene complexes of molybdenum R3E–CH Mo(NAr)(OCMe2CF3)2 (E = Si, Ge; R = Me, Ph) and also hydrocarbon analogs Alkyl-CH Mo(NAr)(OCMe2CF3)2 (Alkyl = But, PhMe2C) in metathesis of 1-hexene were investigated. The catalytic activity of alkylidene complexes was shown to depend essentially on the nature of substituent bonded to carbene carbon atom.