SYNTHESIS AND X-RAY CRYSTAL-STRUCTURES OF HEXAKIS(TRIMETHYLPHOSPHINE)TRIS-MU-METHYLENE-DIRUTHENIUM(III) AND ITS MONO-CATIONIC AND DICATIONIC DERIVATIVES, HEXAKIS(TRIMETHYLPHOSPHINE)-MU-METHYL-BIS-MU-METHYLENE-DIRUTHENIUM(III) TETRAFLUOROBORATE AND HEXAKIS(TRIMETHYLPHOSPHINE)BIS-MU-METHYLENE-DIRUTHENIUM(III) BISTETRAFLUOROBORATEK

The interaction of dimethylmagnesium with the ruthenium(III) trinuclear μ3-0x0 centered acetate, [Ru3O(O2C-Me)6(H2O)3](O2CMe), in the presence of trimethylphosphine yields a unique complex of stoichiometry (Me3P)3Ru(μ-CH2)3-Ru(PMe3)3(1), containing three bridging methylene groups. The interaction of this complex with 1 equiv of tetrafluo-roboric acid yields a 1+ cationic species, [(Me3P)3Ru(μ-CH2)2(μ-CH3)Ru(PMe3)3]BF4(2), in which one μ-CH2group is protonated to give a bridging methyl group. With 2 equiv of acid, a 2+ cationic species, [(Me3P)3Ru(μ-CH2)2Ru(PMe3)3]-(BF4)2, (3), is formed with loss of methane; this contains only two bridging methylene groups. The corresponding trifluorom-ethanesulfonate (4) has also been obtained. The compounds have been studied by1H,31P, and13C NMR spectroscopy and their structures have been determined by X-ray crystallography. The compound 1 crystallizes in space group P21/n with a = 22.174 (5) Å, b = 9.352 (2) Å, c = 16.925 (4) Å, β = 106.06 (3)°, and Z = 4. The structure was solved by direct methods and refined by least squares to a final R of 0.0292 for 4561 observed data. The overall molecular geometry is that of a confacial bioctahedron. The average Ru-C and Ru-P distances are 2.107 and 2.336 Å, respectively. The Ru-Ru distance of 2.650 (1) Å and acute (ç78°) Ru-C-Ru angles are consistent with a single Ru-Ru bond as required by the diamagnetism of the compound. Compound 2 crystallizes in space group Plfn with a = 15.216 (4) Å, b = 9.930 (2) Å, c = 12.579 (2) Å, β = 109.68 (2)°, and Z = 2. The structure was solved via Patterson and electron density syntheses and refined to an R of 0.049 for 3098 observed data. The dinuclear cation has C2symmetry with the bridging CH2group sited on the twofold axis and the second CH2and the CH3groups disordered over the other two equivalent sites. The Ru-C distances are all equal within the limits of experimental error, but the Ru-P bond trans to the unique bridging carbon is longer 2.331 (1) vs. 2.307 (2), 2.314 (2) Å, than the other two. Compound 3 crystallizes in space group Pbca with a = 12.719 (2) Å, b = 16.011 (3) Å, c = 17.765 (2) Å, and Z = 4. This structure was also solved by heavy-atom methods and refined to an R of 0.036 for 2370 observed data. The dinuclear cation has 1 symmetry and thus an accurately planar Ru-C-Ru-C nucleus. Each Ru atom has an approximate square pyramidal coordination with one of the phosphines occupying the axial site. The Ru-P distance to this ligand (2.223 (1) Å) is shorter than those of the others, 2.417, 2.424 (1) Å. The RUC2RU unit is symmetrical, with a mean Ru-C distance of 2.071 (5)Å. © 1979, American Chemical Society. All rights reserved.