Pentacoordination at antimony via endocyclic and exocyclic intramolecular interactions in dibenzostibocine diorganodithiophosphates [{D(C6H4S)(2)}Sb{S2P(OR)(2)}] (D=O, S)

Treatment of [{D(C6H4S)(2)}SbCl] (D = O, 1; D = S, 2) with MS2P(OR)(2) afforded the stable dibenzostibocine dithiophosphate compounds [{D(C6H4S)(2)}Sb{S2P(OR)(2)}] with D = O, R = 1,2-C6H4 (3); for D = S, R = 1,2-C6H4 (4), Et (5), Pr-n (6), Pr-i (7), and Ph (8). The compounds were characterized by IR and H-1, C-13{H-1}, and P-31{H-1} NMR spectroscopy in solution. The P-31{H-1} NMR data are consistent with an anisobidentate coordination mode of the dithiophosphate ligand to the Sb atom. Single crystal X-ray diffraction analyses of compounds 3, 4, 7, and 8 revealed that the antimony atom acts as an acceptor atom exhibiting endocyclic and exocyclic intramolecular interactions with the donor D atom and with both sulfur atoms of the dithiophosphate ligand, expanding its coordination sphere from four in the starting materials to five and displaying a skew-trapezoidal pyramidal local geometry.