STEPWISE FORMATION OF THE BIS(BENZENE)HEXARUTHENIUM CARBIDO CARBONYL CLUSTER RU6C(CO)11(ETA-6-C6H6)(MU-3-ETA-2-ETA-2-ETA-2-C6H6) FROM RU6C(CO)17

A new stepwise synthetic pathway to the bis(benzene)hexaruthenium carbido carbonyl cluster Ru6C(CO)11-(eta6-C6H6)(mu3-eta2:eta2:eta2-C6H6) is described. On treatment with 2 equiv of Me3NO in the presence of 1,3- or 1,4-cyclohexadiene, the parent carbido cluster RU6C(CO)17 (1) affords the new cyclohexa-1,3-diene species Ru6C-(CO)15(mu2-eta2:eta2-C6H8) (2) and the benzene derivative Ru6C(CO)14(eta6-C6H6) (3). Compound 2 may be converted into 3 by reaction with an additional equivalent of Me3NO. Further treatment of 3 with either 1,3- or 1,4-cyclohexadiene affords three complexes, two new benzene/diene species, Ru6C(CO)12(mu3-eta2:eta2:eta2-C6H6)(mu2-eta2:eta2-C6H8) (4) and Ru6C-(CO)12(eta6-C6H6)(mu2-eta2:eta2-C6H8) (5), and the bis(benzene) cluster Ru6C(CO)11(eta6-C6H6)(mu3-eta2:eta2:eta2-C6H6 (6). Cluster 4 may be converted to 5 by heating in hexane. Compound 6 can also be generated from 5 by the addition of a second aliquot Of Me3NO or, alternatively, via the cationic benzene/dienyl intermediate [Ru6C(CO)12(eta6-C6H6)(mu3-eta1:eta2:eta2-C6H7)]+ (7), formed on reaction with Ph3C+. Compound 7 then reacts with DBU (DBU = 1,8-diazabicyclo-[5.4.0]undec-7-ene) to afford 6. The molecular structures of compounds 2-5 have been determined by single-crystal X-ray diffraction analysis. Compound 2 is monoclinic, space group P2(1)/C, with a = 17.723(3) angstrom, b = 9.502(2) angstrom, c = 18.443(5) angstrom, beta = 116.02(2)degrees, Z = 4; compound 3 is orthorhombic, space group P2(1)2(1)2(1), with a = 8.924(6) angstrom, b = 16.332(6) angstrom, c = 18.299 angstrom, Z = 4; compound 4 is orthorhombic, space group Pna2(1), with a = 20.536(3) angstrom, b = 9.843(3) angstrom, c = 13.911(2) angstrom, Z = 4; compound 5 is triclinic, space group P1BAR, with a = 10.314(9) angstrom, b = 10.720(8) angstrom, c = 15.23(1) angstrom, alpha = 74.24(5)degrees, beta = 79.59(5)degrees, gamma = 78.50(4)degrees, Z = 2.