7-COORDINATE MOLYBDENUM COMPLEXES CONTAINING SNRCL(2) AND PHOSPHORODITHIOATE - X-RAY STRUCTURE OF [MO(CO)(2)(P(OME)(3))(2)(S2P(OET)(2))(SNBUCL(2))]

[Mo(Co)(3)(NCMe)(2)(SnRCl(2))Cl] (1a, R=Ph; 1b, R=Bu) react with ammon ium diethyldithiophosphate or with sodium diphenyldithiophosphinate in CH2Cl2 to produce [Mo(CO)(3)(NCMe)(S(2)PX(2))(SnRCl(2))] (2, R = Ph o r Bu; X = OEt or Ph). Upon treatment with an excess of P(OMe)(3), comp lexes 2 undergo substitution of the NCMe and one carbonyl, affording b is(phosphite) complexes [Mo(CO)(2){P(OMe)(3)}(2)(S(2)PX(2))(SnRCl(2))] (3, R = Ph or Bu; X = Oft or Ph). The same complexes are produced by the reaction of dicarbonyltris(phosphite) complexes [Mo(CO)(2){P(OMe)( 3)}(3)(SnRCl(2))Cl] with NH4[S2P(OEt)(2)] or Na[S(2)PPh(2)], through s ubstitution of the chloride ion and one phosphite. The structure of th e derivative 3c (R = Bu, X = OEt) has been determined by X-ray crystal lography. Complexes 3 are fluxional at room temperature as judged by P -31(H-1) NMR spectroscopy. At 195 K, the dynamic process is quenched, giving sharp, well reserved spectra, whose assignment is consistent wi th the solid stale structure.