Pyrazolate thiocarbonylrhodium complexes. X-ray structure of [Rh(μ-3,5-Me 2Pz)(CS)(PPh 3)] 2

Abstract

The preparation and properties of complexes of general formulae [Rh(CS)-(HL)(PR 3) 2]ClO 4 (HL = pyrazole (HPz), 3-methylpyrazole (H3-MePz), 3,5-dimethylpyrazole (H3,5-Me 2Pz), PR 3 = triphenylphosphine, tricyclohexylphosphine) and [(PR 3) 2(CS)Rh(μ-Pz)AuPPh 3]ClO 4 are reported. Complexes of the first set react with potassium hydroxide to give [Rh(μ-L)(CS)(PPh 3) 2 or RhPz(CS)(PR 3) 2 complexes. The structure of the complex [Rh(3,5-Me 2Pz)(CS)(PPh 3)] 2 has been determined by X-ray diffraction methods. The crystals are monoclinic, space group P2 1/ c, with Z = 4 in a unit cell of dimensions a = 12.700(11), b = 17.217(16), c = 23.041(18) Å, β = 116.55(8)°. The structure has been solved by Patterson and Fourier methods and refined by full-matrix least-squares to R = 0.059 for 1978 independent reflections. The structure consists of dimeric complexes, in which each rhodium atom is in a square-planar environment being bonded to a carbon atom of a thiocarbonyl ligand, a phosphorus atom of a triphenylphosphine molecule and to two nitrogen atoms of pyrazolate ligands bridging the metal atoms. The dihedral angle of 71.1° between such two square planes leads to a bent configuration with an intramolecular rhodium-rhodium distance of 3.220 Å. The thiocarbonyl and triphenylphosphine ligands are in a trans disposition.