Cascade-Reaction Leading to an Intramolecular [2 + 4] Cycloaddition of a Phenyl Group by a Reactive Ge═Si Double Bond.

The reaction of GeCl2·dioxane with 2 equiv of the thiolate LiSHyp [Hyp = Si(SiMe3)3] yields the germanide (12-crown-4)2Li[Ge(SHyp)3] (1). A small structural variation in the substituent leads to a completely different result because the reaction of GeCl2·dioxane with 2 equiv of the thiolate KSHypPh3 [HypPh3 = Si(SiMe3)2(SiPh3)] in toluene yields the unexpected compound [Ph3Si][Me3Si]Ge[{(C6H5)Ph2Si}{SiMe3}2SiS]Si[SSiMe3] (2) in high yield. The reaction cascade to give 2 includes several rearrangement reactions and an intramolecular [2 + 4] cycloaddition of a phenyl ring. The syntheses and molecular structures of both compounds are presented, together with quantum-chemical calculations and NMR measurements, to enlighten the reaction mechanism behind the formation of 2.