Phenylantimony(III) derivatives of tetraphenyldichalcogenoimidodiphosphinic acids. Crystal and molecular structure of PhSb[(XPPh2)(SPPh2)N]2 (X=O, S)

The reactions between PhSbCl2 and M[(XPPh2)(YPPh2)N] (M=Na, K; X, Y=O, S), using 1:1 and 1:2 molar ratios, have been investigated. PhSbCl[(XPPh2)(YPPh2)N] and PhSb[(XPPh2)(YPPh2)N]2 were isolated as microcrystalline powders and were characterized using IR and NMR (1H, 31P) spectroscopy. On standing in chloroform solution the chloro derivative PhSbCl[(SPPh2)2N] was found to rearrange to PhSb[(SPPh2)2N]2. The molecular structures of PhSb[(XPPh2)(SPPh2)N]2 (X=O, S) were investigated by X-ray diffraction. The crystals of both compounds contain monomeric units with asymmetric chelating ligand fragments, resulting in a square pyramidal CSbX2S2 core with an apical phenyl group. The antimony lone pair of electrons appears to be stereochemically active and is located trans to the phenyl group, as suggested by the displacement of the metal atom from the best basal plane formed by the chalcogens in the opposite direction with respect to the apical carbon. For the monothio derivative, the molecule displays different ligand behaviour, i.e. O- and S-primary coordinations, respectively.