Reaction of Decamethylsilicocene with Group 13 Element Halides: Insertions, Rearrangements, and Eliminations

Abstract

In the reaction of decamethylsilicocene (1; (Me5C5)2Si) with halides or organohalides of trivalent boron, aluminum, gallium, and indium, quite different and sometimes very complex pathways are observed which include adduct formation, 1,2-halide or -alkyl shifts, 1,2-dyotropic rearrangements, and reductive elimination and oxidative addition reactions. Cp*BCl2 (Cp* = pentamethylcyclopentadienyl), BCl3, and BBr3 reacted with 1 to form the pentacarba-nido-hexaboronium salts [Cp*SiCl2BCp*]+[Cp*BCl3]- (3a) and [Cp*SiX2BCp*]+[BX4]- (3b, X = Cl; 4, X = Br). A second product (5b) of composition Cp*3Si2Br4B with an arachno-cluster framework was isolated from the reaction with BBr3. With AlCl3 and AlBr3 metathesis reactions gave the ionic compounds [Cp*2Al]+[AlX4]- (6a,b, X = Cl, Br), respectively. The formation of 6a,b is the result of a Lewis-base-catalyzed dismutation of Cp*AlX2 in which 1 is the base, as proved by separate experiments. The compound Cp*Al(Me)Cl (7) was formed in the reaction of 1 with Me2AlCl. Silicocene 1 functioned as a dehalogenating agent in its reactions with GaCl3, GaBr3, Cp*GaBr2, InCl3, and InBr3, giving the corresponding monovalent, metastable (“GaCl”, “GaBr”) or stable (Cp*Ga, InCl, InBr) species. All new compounds were characterized by NMR (1H, 13C, 11B, 29Si) and mass spectrometry. The solid-state structures of 3a and 5b were determined by X-ray diffraction analysis.