A new approach to cationic transition metal alkyls: [M(η-C5H5)2(CH2SiMe3)2]+[Y]–(M = Nb or Ta, Y = BF4 or SbF6) and their conversion into the alkylidene complexes [M(η-C5H5)2(CHSiMe3)(CH2SiMe3)]

Abstract

The alkylmetal(IV) complex [M(η-C₅H₅)₂R₂](M = Nb or Ta, R = CH₂SiMe₃), obtained from [M(η-C₅H₅)₂Cl₂] and LiR, is oxidised by AgY (Y = BF₄ or SbF₆) in MeCN at 25°C to yield the thermally stable, crystalline, CH₂Cl₂-soluble cationic alkylmetal(V) complex [M(η-C₅H₅)₂R₂]⁺[Y]^–, which may be deprotonated by reaction with Li[N(SiMe₃)₂] in tetrahydrofuran (thf) to give the thermally stable, pentane-soluble, crystalline ylide [M(η-C₅H₅)₂(CHSiMe₃)(CH₂SiMe₃)].