The (Me5C5)Si+ cation: A stable derivative of HSi+

Abstract

The reaction of decamethylsilicocene, (Me5C5) 2Si, with the proton-transfer reagent Me5C 5H2+ B(C6F5) 4- produces the salt (Me5C5)Si + B(C6F5)4- (2), which can be isolated as a colorless solid that is stable in the absence of air and moisture. The crystal structure reveals the presence of a cationic π complex with an η5-pentamethylcyclopentadienyl ligand bound to a bare silicon center. The 29Si nuclear magnetic resonance at very high field (δ = -400.2 parts per million) is typical of a π complex of divalent silicon. The (η5-Me5C5)Si + cation in 2 can be regarded as the "resting state" of a silyliumylidene-type (η1-Me5C5)Si + cation. The availability of 2 opens new synthetic avenues in organosilicon chemistry. For example, 2 reacted with lithium bis(trimethylsityl)amide to give the disilene E-{(η1-Me 5C5)[N(SiMe3)2]Si}2 (3).