SYNTHESIS AND REACTIVITY OF DITHIODIPHENYLPHOSPHINATO-DERIVATIVES OF RHODIUM - CRYSTAL-STRUCTURE OF THE SQUARE-PYRAMIDAL RHODIUM(III) COMPLEX [RHI(ETA-2-S2PPH2)(COME)(PPH3)]

The complexes [Rh2(mu-Cl)2L4](L2 = 1,5-cyclooctadiene (COD); L = CO) react with Na[S2PPh2] to give the mononuclear derivatives [Rh(S2PPh2)L2](L2 = COD, 1; L = CO, 2). Treatment of complex 2 with PPh3 affords [Rh(S2PPh2)(CO)(PPh3)] (3). Complex 3 reacts with iodine to give a mixture of two isomers of [RhI2(S2PPh2)(CO)(PPh3)] (4). A similar reaction of 3 with methyl iodide gives the pentacoordinate rhodium(III) acyl derivative [RhI(S2PPh2)(COMe)(PPh3)] (5). which has a square-pyramidal geometry with the acyl group in the apical position, as determined by X-ray diffraction. The cationic nitrosyl derivative [Rh(S2PPh2)(NO)(PPh3)]BF4 (6) has been prepared by reaction of complex 3 with NOBF4. Neither complex 1 nor complex 3 is a catalyst precursor for the homogeneous hydrogenation of alkenes and alkynes.