Synthesis and reactivity of some t-butyl-disilanes and -digermanes

Abstract

Efficient methods of coupling R2EHCl (R = Me, t-Bu; E = Si, Ge) to give R2HEEHR2 have been developed. These dihydrides are readily halogenated with Br2 or I2 to give the corresponding 1,2-dihalo-disilane or -digermane. High yields of Me2ClGeGeClMe2 are obtained by treating hexamethyldigermane with conc. sulfuric acid and ammonium chloride. Conc. sulfuric acid exclusively cleaves methyl groups from [t-BuMe2Ge--]2 to give [t-BuMeClGe--]2 after treatment with ammonium chloride. The latter dichlorodigermane is formed as a mixture of d,l-enantiomers and the meso isomer as shown by NMR evidence. The bulky t-butyl groups render (t-Bu)4Si2Br2 inert to nucleophilic substitution or metal--halogen exchange with organolithium reagents.