SYNTHESES AND REACTIONS WITH LEWIS-BASES OF RU-4(CO)(8)(MU(3)-O(2)C(6)H(2)R(2))(2) (R=H, T-BU), COMPLEXES CONTAINING 1,2-SEMIQUINONE LIGANDS WHICH BRIDGE THROUGH OXYGEN AND ETA(6)-C-6 RINGS - CRYSTAL-STRUCTURES OF RU-4(CO)(8)(O2C6H4)(2)CENTER-DOT-CH2CL2, RU-4(CO)(8)(O2C6H2(T-BU)(2))(2)CENTER-DOT-2CH(2)CL(2), RU-4(CO)(8)(O2C6H2(T-BU)(2))(2)(PY)(2), AND RU-4(CO)(7)(O2C6H2(T-BU)(2))(2)(PHC-CCO(2)ET)

The reactions of Ru-3(CO)(12) with catechol and with 3,5-di-tert-butyl-1,2-benzoquinone yield three clusters Ru-4(CO)(8)(mu(3)-O(2)C(6)H(2)R(2))2, R = H or t-Bu, which differ in the arrangement of metal atoms but which all contain mu(3)-semiquinone ligands coordinated via terminal and bridging O atoms and a pi-eta(6)-C-6 ring. One isomer, designated 1:3, has a structure containing a linear array of three Ru atoms connected by metal-metal bonds and with each pair of metal atoms bridged by one dioxolene ligand through an oxygen atom and an eta(6)-C-6 ring, while the fourth Ru atom is connected via bridging oxygen atoms from the two dioxolene ligands. The other isomer, designated 2:2, contains two diruthenium units, each pair of Ru atoms connected via a metal-metal bond and a dioxolene ligand bridge via an oxygen atom and a eta(6)-C-6 ring, and the two Ru-2 units are connected via bridging oxygen atoms from both dioxolene ligands. The 1:3 isomer Ru-4(O2C6H2(t-Bu)(2))(2)(CO)(8) does not react directly with Lewis bases but reacts with trimethylamine N-oxide in THF or acetonitrile to form Ru-4(O2C6H2(t-Bu)(2))(2)(CO)(7)L, L = THF or NCMe, respectively. The THF complex reacts with L = PPh(3), trans-EtO(2)CCH=CHCO (2)Et, C-2(CO(2)Me)2, PhCCCO(2)Et, or C(2)Ph(2) to yield Ru-4(O2C6H2(t-Bu)(2))(2)(CO)(7)L. The analogous 2:2 isomer undergoes fragmentation in the presence of most Lewis bases but rapidly and reversibly reacts with pyridine to form Ru-4(O2C6H4(t-Bu)(2))(2)(CO)8(py)(2). Four X-ray diffraction studies are reported. Ru-4(CO)(8)(O2C6H4)(2).CH2Cl2 crystallizes in the noncentrosymmetric orthorhombic space group Pnn2 with a 13.9003(20) Angstrom, b = 8.6481(21) Angstrom, c = 10.6075(16) Angstrom, V = 1215.1(4) Angstrom(3), and Z = 2. The structure was refined to R = 1.92% for 1572 reflections above 6 sigma. The molecule has C-2 symmetry with a close-to-linear array of three Ru atoms, the two terminal metal atoms being linked to eta(6)-O2C6H4 ligands and two CO ligands; the central Ru and the ''lone'' Ru atom are each bonded to two CO ligands and are bridged by the oxygen atoms of the O2C6H4 ligands. Ru-4(CO)(8)(O2C6H2(t-Bu)(2))(2).2CH(2)Cl(2) crystallizes in space group P1 with a 11.3503(13) Angstrom, b = 11.4188(11) Angstrom, c = 19.4541(19) Angstrom, alpha = 93.680(8)degrees, beta = 102.682(8)degrees, gamma = 107.260(8)degrees, V = 2326.3(4) Angstrom(3), and Z = 2. The structure was refined to R = 4.34% for 3540 reflections above 6 sigma. The ruthenium-containing molecules have C-i symmetry. The molecule is composed of two [eta(6)-O2C6H2(t-Bu)(2)]Ru(CO)(2)-Ru(CO)(2) units which are held together by additional Ru-O linkages. Ru-4(CO)(8)(O2C6H2(t-Bu)(2))(2)(py)(2) crystallizes in space group P2(1)/n with a 12.5406(16) Angstrom, b = 23. 9907(34) Angstrom, c = 16.5219(19) Angstrom, beta = 91.989(10)degrees, V = 4967.8(11) Angstrom(3), and Z = 4. The structure was refined to R = 2.85% for 2833 reflections above 6 sigma. The molecule is not symmetrical, but consists of [eta(6)-O2C6H2(t-Bu)(2)](OC)(2)Ru-Ru(CO)(2)(py) and [eta(6)-O2C6H2(t-Bu(2))](OC)Ru(mu-CO)(2)Ru(CO)(py) units held together by Ru-O linkages. The C-13 NMR spectrum indicates that the same structure is adopted in solution; surprisingly, even though pairwise bridge-terminal carbonyl exchange would interconvert the two Ru-2 subunits, the molecule is rigid on the NMR time scale at room temperature. Ru-4(CO)(7)(O2C6H2(t-Bu)(2))(2)(PhC equivalent to CCO(2)Et) crystallizes in the noncentrosymmetric orthorhombic space group P2(1)2(1)2(1) with a = 12.4149(19) Angstrom, b = 16.0888(27) Angstrom, c = 23.9674(31) Angstrom, V = 4787.3(13) Angstrom(3), and Z = 4. The structure was refined to R = 5.01% for 3782 reflections above 6 sigma. The molecule has a connectivity similar to that of Ru-4(CO)(8)(O2C6H4)(2) but with an alkyne ligand substituting for a CO on the ''lone'' Ru atom.