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

Abstract

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