RHODIUM PALLADIUM AND RHODIUM PLATINUM HETEROBINUCLEAR COMPLEXES CONTAINING THE 2-(DIPHENYLPHOSPHINO)PYRIDINE SHORT-BITE BRIDGING LIGAND - X-RAY CRYSTAL-STRUCTURE OF [(ETA-5-C5H5)(CNBUT)RH(MU-PH2PPY)PD(CNBUT)CL]PF6

Some new RhPd and RhPt heterobinuclear complexes containing the 2-(diphenylphosphino)pyridine (Ph2PPy) bridging ligand have been prepared by reacting [Rh(eta-5-C5H5)(CO)(Ph2PPy)] (1) with d8 palladium(II) and platinum(II) complexes. The reaction of 1 with cis-[Pd(CNBu(t))2Cl2] gave [(eta-5-C5H5)(CNBu(t))Rh(mu-Ph2PPy)Pd(CNBu(t))Cl]Cl (2b); if the reaction was performed in the presence of TIPF6, the corresponding PF6- salt (2a) was isolated. The structure of 2a, containing benzene and methanol molecules of solvation, has been determined by X-ray crystallography. The crystal is monoclinic, with space group P2(1)/n, and the cell constants are a = 24.485 (3) angstrom, b = 10.262 (2) angstrom, c = 17.626 (3) angstrom, beta = 101.40 (4)-degrees, and Z = 4. The structure has been refined to a final R value of 0.045. The cation consists of the (eta-5-C5H5)(CNBu(t))Rh and (CNBu(t))ClPd moieties held together by the Ph2PPy bridge and and the Rh-Pd bond. The Pd atom exhibits a nearly square-planar coordination geometry, and the ligands about rhodium are disposed in a distorted tetrahedral environment. The angles at rhodium between the centroid of the cyclopentadienyl ring and the other ligands are larger than those formed by the other ligands. The Rh-Pd bond distance is 2.631 (2) angstrom; the Ph2PPy is twisted by 35.4 (2)-degrees about the Rh-Pd bond to avoid unfavourable contacts. Compound 2b readily undergoes metathesis with KI, giving the corresponding iodo derivative [(eta-5-C5H5)(CNBu(t))Rh(mu-Ph2PPy)Pd(CNBu(t))I]I (4); compound 4 was also the product of the reaction of 2b with CH3I or CH2I2. The reaction of 1 with [Pd(COD)Cl2] (COD = cycloocta-1,5-diene) occurs by displacement of COD to give [(C5H5)Rh(CO)(mu-Ph2PPy)PdCl2], (5). Reaction of 1 with cis-[Pt-(DMSO)2((CH3)2] (DMSO = dimethyl sulfoxide) gave the compound [(eta-5-C5H5)Rh(mu-CO)(mu-Ph2PPy)Pt(CH3)2] (6) in which a rhodium-platinum bond is present. The analogous reaction with cis-[Pt(DMSO)2Cl2] yielded the Rh(II)-Pt(I) complex ](eta-5-C5H5)RhCl(mu-Ph2PPy)Pt(CO)Cl] (8); the reaction formally involves the oxidative addition of a d8 platinum species to a d8 five-coordinated rhodium(I) complex. The results show that the rigid short-bite Ph2PPy ligand and the nature of the ligands coordinated to palladium(II) or platinum(II) complexes strongly influence the course of the reactions described.