PRODUCTS OF THE REDOX REACTIONS OF CIS-RE2(O2CCH3)2CL4L2 (L = H2O, PY) WITH BIS(DIMETHYLPHOSPHINO)METHANE AND THE ISOLATION AND STRUCTURAL CHARACTERIZATION OF A GROSSLY UNSYMMETRICAL MIXED-VALENT DIRHENIUM COMPLEX OF COMPOSITION RE2O3CL2(DMPM)2

The reaction of cis-Re2(O2CCH3)2Cl4(H2O)2 with Me2PCH2PMe2 (dmpm) in ethanol/toluene at room temperature affords a separable mixture of Paramagnetic Re2(mu-O2CCH3)Cl4(mu-dmpm)2 and diamagnetic Re2Cl4(mu-dmpm)3 and Re2O3Cl2(dmpm)2. The corresponding reactions of cis-Re2(O2CC2H5)2Cl4(H2O)2 and cis-Re2(O2CCH3)2Br4(H2O)2 with dmpm give primarily Re2(mu-O2CC2H5)Cl4(mu-dmpm)2 and Re2(mu-O2CCH3)Br4(mu-dmpm)2, respectively, along with small amounts of Re2X4(mu-dmpm)3 (X = Cl, Br). A higher yield (ca. 80%) synthetic route to Re2(mu-O2CCH3)X4(mu-dmpm)2 (X = Cl, Br), which utilizes cis-Re2(O2CCH3)2X4(py)2 in place of the aquo adduct, does not involve the formation of other products. The complex Re2(O2CCH3)Cl4(dmpm)2 reacts with dmpm in hot ethanol/toluene to produce Re2Cl4(mu-dmpm)3. The oxo complex of composition Re2O3Cl2(dmpm)2 is the novel mixed-valent compound O3ReReCl2(dmpm)2 whose rhenium centers are formally Re(VI) and Re(II) and which contains a short, unsupported Re-Re bond (2.4705 (5) angstrom) and a remarkable disparity in the metal coordination numbers (4 and 7). Crystal data at 20-degrees-C: monoclinic space group P2(1)/c, a = 15.033 (2) angstrom, b = 18.707 (2) angstrom, c = 14.790 (2) angstrom, beta = 100.833 (8)-degrees, V = 4085 (2) angstrom3, Z = 8. The structure was refined to R = 0.033 (R(w) = 0.043) for 4561 data with I > 3-sigma(I). NMR spectral studies indicate that this basic structure is retained in solution.