Sn[Si(SiMe3)3]3- and Sn3[Si(SiMe3)3]4: first insight into the mechanism of the disproportionation of a tin monohalide gives access to the shortest double bond of tin.

In the course of the disproportionation reaction of a monohalide beside metalloid clusters like Sn(10)[Si(SiMe(3))(3)](6) also molecular compounds with an average oxidation state of the tin atoms larger than one must be present. First results of such oxidized species are presented where the bonding is strongly influenced by the steric bulk of the ligands leading to the shortest tin-tin double bond.