Synthesis of a Stable Complexed Stannylene [(R₃Si)₂Sn:]

Much attention has been focused on the preparation and reactivity of tetrylenes, divalent group-14 elements R₂E: (E= Si, Ge, Sn). In this work we focus on stannylenes which are important reagents in organic synthesis. There are two common methods for their preparation: (a) substitution reaction of SnCl₂ with organometallic species; (b) reduction of the corresponding dihalides, R₂SnX₂. The major drawbacks of both methods are the relatively low yields of the desired stannylene and the necessity to separate it from salts.

Recently, we found that intermediate bis(silyl)stannylenes can be generated conveniently under mild conditions from trisilyl - substituted tin hydrides (Scheme, step a) and can be trapped by several reagents. In the case of (tBu₂MeSi)₃SnH (1), the intermediate bis(silyl)stannylene (2) dimerizes instantaneously yielding distannene (4) (Scheme, step b). However, when 2 is generated in the presence of NHC^Me, quantitative conversion to carbene-stannylene complex (3) is obtained (Scheme, path c). In contrast to free stannylene 2, NHC^Me complexed stannylene 3 does not dimerize.

In recent years, the chemistry of R₂E: coordinated by NHC attracts wide interest. Now, that we have both the uncomplexed stannylene 2 and the NHC^Me complexed stannylene 3, we plan to compare their reactivities with various compounds.

Scheme