Binuclear complexes of rhodium(II) bridged by anionic [formula omitted] ligands and X-ray crystal structure of tetrakis(μ-5-methylthio-2-mercaptothiadiazolinato)triphenylphosphinodirhodium

Abstract

Reactions of the binuclear complex [Rh(OCOCH 3) 2] 2 with bifunctional anionic heterocyclic ligands such as 5- substituted 2-mercaptothiadiazolines, 4,5-substituted 3-mercaptotriazoles or thiazolidine-2-thione in the presence of a base yield the binuclear complexes Rh{μ-( NS ) 2(OCOCH 3) 2}·2L where NS is the monoanionic group listed and L=PPh 3, P(OR) 3 or Py. With a large excess of the anionic ligand, fully substituted products of the type [Rh(μ- NS ) 2] 2L are obtained. These complexes are characterized by IR, 1H NMR and electronic spectroscopy. The structure of the 3-mercapto-5-methylthio-1-2-thiadiazolinate bridged rhodium complex [Rh(DMTH) 2] 2PPh 3 has been determined by X-ray crystallography. This compound, C 30H 27N 8PS 12Rh 2, formula weight=1121.2, crystallizes in the space group P2 1/ a with a=20.403(2), b=9.752(2), c=23.176(1) Å, β=112.77(1)°, V=4252.0(5) Å 3, Z=4. The prominent feature of this compound is the bridging arrangement in which all four sulfur atoms and a triphenylphosphine group are bound to one rhodium while the other rhodium atom is bound equatorially to four nitrogen atoms, the axial position being vacant. The RhP distance is 2.350(2) Å, with the Rh(1)Rh(2)P angle of 174.1(1)°. The geometry around Rh(2) is distorted octahedral, while that around Rh(1) is square- pyramidal. The Rh(1)Rh(2) distance is 2.603(1) Å.