Syntheses and structures of dimesitylbismuth(III) bromide, Mes2BiBr, and bis(diphenyldithiophosphinato)mesitylbismuth(III), MesBi(S2PPh2)2

Article abstract of DOI:10.1016/0022-328X(94)80152-5

Addition of BiBr3 to Mes3Bi (Mes = 2,4,6-Me3C6H2) in Et2O gives 86percent of Mes2BiBr (1) as yellow crystals.Reaction of 1 with Ph2PS2NH4 in a 1:1 molar ratio gives a quantitative yield of MesBi(S2PPh2)2 (2) rather than the expected dimetysilbismuth compound.The crystal and molecular structures of 1 and 2 were determined at 153 K and 173 K, respectively.They contain Mes2BiBr molecules with trigonal pyramidal coordination around Bi.The mean Bi-C bond distance is 2.27 Angstroem and the Bi-Br bond distance is 2.690(2) Angstroem.The angles around Bi vary between 89.4 and 106.4 deg.Intermolecular Bi...Br contacts of 3.795 Angstroem, indicating weak secondary bonding, give rise to zig-zag shaped (Bi-Br)x chains.In the polymeric chain the coordination geometry around bismuth atoms can be described as pseudo-trigonal bipyramidal.The crystals of 2 consist of discrete monomeric MesBi(S2PPh2)2 molecules with a symmetry plane containing the metal atom and the aromatic ring of the attached mesityl group.The dithiophosphinato ligands exhibit an anisobidentate coordination pattern with long and short phosphorus-sulfur bonds, i.e.P(1)-S(1) 2.051(31) Angstroem and P(1)-S(2) 1.980(3) Angstroem, related to short and long bismuth-sulfur distances, respectively, i.e.Bi-S(1) 2.662(2) Angstroem and Bi-S(2) 3.123(3) Angstroem.This leads to a square-pyramidal geometry around the bismuth atom, with the metal lying 0.33 Angstroem above the basal plane formed by the four sulfur atoms. Key words: Bismuth; Mesityl; Phosphorus; Bromide; Crystal structure