(Tetramethylcyclobutadiene)cobalt complexes with tricarbollide ligands

Abstract

Reactions of the 11-vertex nido-tricarbollide anions [7,8,9-C 3B8H11]- (2a) and [7,8,10-C 3B8H11]- (3) with [Cb*Co(MeCN)3]+ or [Cb*Co(C6H 6)]+ (Cb* = C4Me4) afford the expected cobaltatricarbollides 1-Cb*-1,2,3,4-CoC3B 8H11 (4a) and 1-Cb*-1,2,3,5-CoC3B 8H11 (5), respectively. A similar reaction of the ammo-substituted anion [7-tBuNH-7,8,9-C3B8H 10]- (2b) is accompanied by polyhedral rearrangement even at room temperature, giving 1-Cb*-12-tBuNH-1,2,4,12-CoC3B 8H10 (7b). Complex 4a rearranges to the isomeric complex 5 at 110°C and further to 1-Cb*-1,2,4,10-CoC3B 8H11 (6a) at 160°C. The amino-substituted derivative 1-Cb*-10-tBuNH-1,2,4,10-CoC3B8H10 (6b) was obtained by isomerization of 7b at 160°C. The observed rearrangement sequence for Cb*CoC3B8H11 correlates well with the relative stabilities of nonmethylated analogs estimated by DFT calculations. The structures of 4a and 7b were determined by X-ray diffraction. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.