SYNTHESIS AND X-RAY CHARACTERIZATION OF TETRAPHENYLPHOSPHONIUM TETRATHIOCYANATODIOXOMOLYBDATE(VI) - A REMARKABLE OXO TRANSFER AGENT

The tetraphenylphosphonium salt of the anion [Mo(VI)(O)2(NCS)4] is prepared from sodium molybdate and potassium thiocyanate in acidic medium, followed by cation exchange under phase transfer conditions. The crystalline compound belongs to the tetragonal space group P4(1)2(1)2, with a = b = 12.802(3) angstrom and c = 31.820(4) angstrom. The volume of the unit cell is 5215 angstrom3 with Z = 4. The structure was refined to R = 8.9%. The title compound is found to catalyze the oxygen transfer from dimethyl sulfoxide to triphenylphosphine approximately 20 times more efficiently than the known dioxobis(N,N'-diethyldithiocarbamato)molybdenum(VI) complex.