The first structurally characterised example of silicon in an S6 coordination sphere

The reaction of sodium hydro-tris(phenylthioimidazolyl)borate (NaTmPh) with silicon tetraiodide gives rise to the first crystallographically characterised molecular silicon compounds, [Si(TmPh)2] 2X (X = I- and I3- ), in which the silicon is found in a regular S6 environment. The [Si(TmPh)2]2+ cation is subjected to analysis using DFT methods to explain why an S6 coordination motif is preferred to an S4 coordination motif.