UNEXPECTED LINEAR P-N-P FRAGMENT IN THE ANION [SPH(2)PNPPH(2)S](-) - CRYSTAL-STRUCTURE OF BIS(TRIPHENYLPHOSPHINE)IMINIUM DITHIOTETRAPHENYLIMIDODIPHOSPHINATE, [PH(3)PNPPH(3)](-)()[SPH(2)PNPPH(2)S]()

The structure of [Ph(3)PNPPh(3)](+) [SPh(2)PNPPh(2)S](-) was determine d by single crystal X-ray diffraction. The cation displays the usual b ent conformation [P-N-P 143.0(5)degrees] and long P-N bonds (1.577(3) Angstrom). This salt represents the first example of a linear SPh(2)PN PPh(2)S(-) anion (P-N-P 180 degrees) with short P-N bonds [1.554(2)Ang strom]. The structures of the bent and linear forms of the [Ph(3)PNPPh (3)](+) cation and [SPh(2)PNPPh(2)S](-) anion can be rationalized in t erms of P-N single and double bond contributions to the resonance stru ctures describing them.