RHENIUM PLATINUM MIXED-METAL CLUSTERS - SYNTHESIS AND SOLID-STATE STRUCTURAL CHARACTERIZATION OF [RE2PT(MU-H)2(CO)8(COD)] AND OF [RE3PT(MU-H)3(CO)14]

The reaction of [Re2(mu-H)2(CO)8] with 1 equiv of Pt(COD)2 (COD = 1,5-cyclooctadiene) affords quantitatively the triangular cluster [Re2Pt(mu-H)2(CO)8(COD)], characterized spectroscopically and by X-ray analysis. The crystals are monoclinic, space group P2(1), with a = 7.217 (3) angstrom, b = 17.081 (5) angstrom, c = 8.577 (3) angstrom, beta = 109.96 (3)-degrees and Z = 2. The refinements, based on 2037 significant reflections, gave final agreement indices R and R(W) of 0.021 and 0.025, respectively. The ligand COD can be easily substituted by two PPh3 molecules. On the contrary, the reaction with 2 equiv of CO, at 190 K, leads to the substitution of COD by one CO and one HRe(CO)5 molecule, giving the complex [Re3Pt(mu-H)3(CO)14], whose structure has been elucidated by X-ray analysis. It gives triclinic crystals, space group P1, with a = 11.764 (1) angstrom, b = 13.737 (4) angstrom, c = 15.787 (3) angstrom, alpha = 64.83 (2)-degrees, beta = 83.36 (1)-degrees, gamma = 89.19 (2)-degrees, and Z = 4. The refinements, based on 4461 significant reflections, gave final agreement indices R and R(W) of 0.031 and 0.032, respectively. The structure contains a tetrametal cluster consisting of a Re2Pt triangle plus a Re atom, which belongs to an unusual HRe(CO)5 two-electron donor ligand, bound to the platinum atom. The H-1 NMR spectrum of this complex shows, at 180 K, the presence of two isomers.