SYNTHESIS OF HEXARUTHENIUM BIS(ARENE) CLUSTERS - MOLECULAR AND CRYSTAL-STRUCTURE OF [RU6C(CO)11(ETA-6-1,3,5-C6H3ME3)(ETA-6-C6H6)] AND [RU6C(CO)11(ETA-6-1,3,5-C6H3ME3)2]

Treatment of [Ru6C(CO)14(eta6-1,3,5-C6H3Me3)] with 2 equiv of Me3NO in CH2Cl2 in the presence of 1,3-cyclohexadiene yields the mixed arene-diene derivative [RU6C(CO)12(eta6-1,3,5-C6H3Me3)(eta4-C6H8)] (2). Further reaction of 2 with Me3NO/CH2Cl2 produces [Ru6C(CO)11(eta6-1,3,5-C6H3Me3)(mu3:eta2:eta2:eta2-C6H6)] (3), which, on standing, converts to a second isomer [Ru6C(CO)11(eta6-1,3,5-C6H3Me3)(eta6-C6H6)] (4). In a similar sequence of reactions employing 1,3,5-C6H5Me3, the complexes [Ru6C(CO)12(eta6-1,3,5-C6H3Me3)(eta4-1,3,5-C6H5Me3)] (5) and Ru6C(CO)11(eta6-1,3,5-C6H3Me3)2] (6) have been obtained. The molecular structures of 4 and 6 in the solid state have been characterized by single-crystal X-ray diffraction. Complex 4 is orthorhombic, space group Pbca, with a = 15.996 (5) angstrom, b = 15.997 (5), c = 23.81 (1) angstrom, V = 6093.7 angstrom3, Z = 8, D(c) = 2.45 g.cm-3, F(000) = 4256, final R = 0.035, and R(w) = 0.033 for 1728 out of 5896 independent reflections [I0 > 2sigma(I0)]; 6 is monoclinic, space group P2(1)/c, with a = 10.084 (1) angstrom, b = 16.984 (3) angstrom, c = 19.425 (5) angstrom, beta = 88.94 (1)-degrees, V = 3326.4 angstrom3, Z = 4, D(c) = 2.33 g.cm-3 , F(000) = 2224, final R = 0.032, and R(w) = 0.035 for 4437 out of 6321 independent reflections [I0 > 2sigma(I0)]. It has been shown that in 4 the two arenes are terminally bound on adjacent ruthenium atoms, while in 6 the Ru6C-cluster unit is sandwiched between the two mesitylene ligands. The molecular organization in crystalline 4 and 6 has been investigated by empirical packing potential energy calculations showing that, in both cases, the arene ligands establish graphitic-like intermolecular interactions in the lattice.