A strongly twisted SiSi bond with resemblance to a buckled dimer in an unexpected isomer of hexasilabenzene.

The reductive debromination of {N(SiMe 3 )Ph}SiBr 3 1 with Rieke magnesium yields the six-vertex amido-substituted silicon cluster 2 with zwitterionic character that represents an unprecedented isomer of hexasilabenzene. The topology of Si1 and Si2 in 2 has bonding features of a highly twisted disilene and resembles that of a buckled dimer of Si(100)2 × 1 reconstructed surfaces. Cluster 2 forms the adducts 3 and 4 with NHC Me4 and DMAP, respectively. The NHC adduct 4 additionally coordinates to BH 3 which affords the saturated cluster BH 3 NHC Me4 Si 6 {N(SiMe 3 )Ph} 6 (5). Furthermore, 2 undergoes addition with MeI and iodine to form the halogenated silicon clusters 6 and 7, respectively.