The disproportionation reaction of the subvalent metastable halide SnBr proved to be a powerful synthetic method for the synthesis of metalloid cluster compounds of tin. Hence, the neutral metalloid cluster compound Sn-10[Si(SiMe3)(3)](6) (3) was synthesized from the reaction of SnBr with LiSi(SiMe3)(3). In the course of the reaction anionic clusters might also be present, and we now present the first anionic cluster compound {Sn8E[Si(SiMe3)(3)](3)}(-) (E = Si, Sn), where one position in the cluster core is occupied by a silicon or a tin atom, giving further insight into structural variations of E-9 cages in metalloid group 14 cluster compounds.