Synthesis and some properties of 14 group element-containing alkylidene complexes of molybdenum and tungsten

Abstract Alkylidene complex of molybdenum Ph 3 Si–CH Mo(NAr)(OCMe 2 CF 3 ) 2 ( 1 ) ( Ar = 2 , 6 - Pr 2 i C 6 H 3 ) has been prepared by the reaction of Ph 3 SiCH CH 2 with known alkylidene compounds Alkyl-CH Mo(NAr)(OCMe 2 CF 3 ) 2 (Alkyl = Bu t , PhMe 2 C). 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) 2 M(CH 2 EMe 3 ) 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 1 H NMR spectroscopy in the reactions of (ArN) 2 W(CH 2 EMe 3 ) 2 (E = Si, Ge, Sn) with hydrogen chloride in THF- d 8 . Catalytic properties of heteroelement-containing alkylidene complexes of molybdenum R 3 E–CH Mo(NAr)(OCMe 2 CF 3 ) 2 (E = Si, Ge; R = Me, Ph) and also hydrocarbon analogs Alkyl-CH Mo(NAr)(OCMe 2 CF 3 ) 2 (Alkyl = Bu t , PhMe 2 C) 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.