Addition of methyllithium to disilyne RSi SiR (R = SiiPr[CH(SiMe3)(2)]), giving a disilenyllithium, and its unexpected isomerization to a disilacyclopropylsilyllithium

The reaction of the isolable disilyne 1, RSi SiR (R = SiiPr[CH(SiMe3)(2)]), with MeLi produced the methyl-substituted disilenyllithium 2 as the primary product. However, 2 is not thermally stable at room temperature in THF, and slowly isomerized to the unexpected disilacyclopropylsilyllithium, which was characterized by NMR spectroscopy as well as by X-ray crystallography.