Preparation and characterisation of anionic bis(cyclopentadienyl)niobium complexes: molecular structure of [K(18-crown-6)][Nb(η-C5H5)2(SnMe3)2]

Abstract

The reaction between [Nb(η-C₅H₅)₂H₃] and LiBu, LiBu-1,4,7,10-tetraoxacyclododecane(12-crown-4), NaH–1,4,7,10,13-pentaoxacyclopentadecane(15-crown-5), KH-1,4,7,10,13,16-hexaoxacyclo-octadecane(18-crown-6), or NaNH₂ gives M[Nb(η-C₅H₅)₂H₂](M = Li, 1; or Na, 5) and [M(crown)][Nb(η-C₅H₅)₂H₂][M(crown)= Li(12-crown-4)2, Na(15-crown-5)3 or K(18-crown-6)4]. The compound SnMe₃Cl reacts with 1 or 4 to give [Nb(η-C₅H₅)₂H₂(SnMe₃)]. The hydrides [Nb(η-C₅H₅)₂H₂(SnMe₃)] and [Nb(η-C₅H₅)₂H(SnMe₃)₂] react with LiBu–12-crown-4, NaNH₂–15-crown-5 and KH–18-crown-6 to give [M(crown)][Nb(η-C₅H₅)₂H(SnMe₃)][M(crown)= Li(12-crown-4), Na(15-crown-5)7 or K(18-crown-6)8] and [M(crown)][Nb(η-C₅H₅)₂(SnMe₃)₂][M(crown)= Li(12-crown-4)9, Na(15-crown-5)10 or K(18-crown-6)11], respectively. The X-ray crystal structure of 11 shows there to be two separate ions [Nb(η-C₅H₅)₂(SnMe₃)₂]^– and [K(18-crown-6)]⁺ with no close interionic contacts. Structural and spectroscopic evidence is presented for the presence of Nb–H–M interactions, where M = Li, Na or K.