Synthesis and characterization of η 5-cyclopentadienyl–silylallyl niobium and tantalum complexes

Abstract

Reaction of the disilylcyclopentadiene 1,1-[SiMe 2(CH 2CH CH 2)] 2C 5H 4 with NbCl 5 gave the new allylsilyl-substituted monocyclopentadienyl niobium complex [Nb{η 5-C 5H 4SiMe 2(CH 2CH CH 2)}Cl 4]. This compound was reacted with LiNH tBu or NH 2 tBu to give the imido derivative [Nb{η 5-C 5H 4SiMe 2(CH 2CH CH 2)}(N tBu)Cl 2], which was further alkylated to the imido alkyl complexes [Nb{η 5-C 5H 4SiMe 2(CH 2CH CH 2)}(N tBu)R 2] (R = Me, CH 2Ph) and [Nb{η 5-C 5H 4SiMe 2(CH 2CH CH 2)}(N tBu)Cl (CH 2Ph)]. Reaction of the imido complexes with the corresponding lithium cyclopentadienides gave the dicyclopentadienyl-imido complexes [M(η 5-C 5R 5){η 5-C 5H 4SiMe 2(CH 2CH CH 2)}(N tBu)Cl] (M = Nb, Ta; R = H, Me). Metallocene dichlorides [M(η 5-C 5R 5){η 5-C 5H 4SiMe 2(CH 2CH CH 2)}Cl 2] (M = Nb, Ta; R = H, Me) were easily prepared by reduction with Na/Hg and simultaneous transmetallation of [Ta(η 5-C 5R 5)Cl 4] with Li[C 5H 4SiMe 2(CH 2CH CH 2)] and of [Nb{η 5-C 5H 4SiMe 2(CH 2CH CH 2)}Cl 4] with Li(C 5R 5). All of the new compounds have been characterized by elemental analysis, and IR and NMR spectroscopy.