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

The reductive debromination of {N(SiMe3)Ph}SiBr3 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 x 1 reconstructed surfaces. Cluster 2 forms the adducts 3 and 4 with NHCMe4 and DMAP, respectively. The NHC adduct 4 additionally coordinates to BH3 which affords the saturated cluster (BH3NHCSi6)-Si-Me4{N(SiMe3)Ph}(6) (5). Furthermore, 2 undergoes addition with MeI and iodine to form the halogenated silicon clusters 6 and 7, respectively.