STRUCTURAL DEPENDENCIES OF PYRAMIDAL SULFUR INVERSION IN HALOGENOTRICARBONYLRHENIUM(I) COMPLEXES OF MONO-(ORTHO-METHYLTHIO) AND BIS-(ORTHO-METHYLTHIO) DERIVATIVES OF TRIPHENYLPHOSPHINE

A series of new halogenotricarbonylrhenium(I) complexes of the hybrid sulphurphosphine ligands [omicron-(methylthio)phenyl]diphenylphosphine (SP) and bis-[omicron-(methylthio)phenyl]phenylphosphine (DSP) have been prepared and characterized. Both ligands act as sulphur/phosphorus mono-chelates, despite the potential tridenticity of DSP. No evidence of an intramolecular methylthio exchange process involving the uncoordinated and coordinated SMe groups was detected in the [ReX(CO)3(DSP)] (X = Cl, Br, I) complexes, in contrast to the analogous [PdX2(DSP)] and [PtX2(DSP)] complexes. Solution NMR studies revealed pyramidal inversion of the coordinated sulphur atoms in the [ReX(CO)3(SP)] and [ReX(CO)3(DSP)] complexes, with energy barriers [DELTA-G++(298 K)] in the range 51-55 kJ mol-1.