Aspects of the Hydrogenation of Carbon Disulfide by Transition-Metal Cluster Compounds. The Reactions of Carbon Disulfide with Hydridotriosmium-Carbonyl Clusters

The reactions of CS2 with H2Os3(CO)10 (la) and H2Os3(CO)9[P(CH3)2C6H5] (lb) are reported. Both clusters react with CS2 to produce dicluster complexes of formula (µ-S2CH2) [HOs3(CO)9L]2 (L = CO, lia; L = P(CH3)2C6H5, lib). Ila was analyzed crystallographically: space group PI, a = 10.093 (3) A, b = 13.289 (2) Å, c = 13.865 (3) A, a = 84.53 (2)°, β = 75.44 (2)°, 7 = 88.24 (2)°, Z = 2, Pcalcd = 3.30 g/cm3. For 3795 reflections (F2 ≥ 3o(F)2) R = 0.048 and Rv = 0.055. Ila contains a methanedithiolato ligand linking two triosmium clusters. The C-S distances at 1.85 Å are typical of carbon-sulfur single bonds. The S-C-S angle at 104.4 (7)° is approximately tetrahedral. In the formation of Ila two cluster complexes have reacted with a single molecule of CS2 and each has transferred one hydride ligand to the carbon atom. A dithioformato complex (ai-S2CH)HOs3(CO)9[P(CH3)2C6H5] (Illb) and a thioformaldehyde complex (m-SCH2)(m3-S)Os3(CO)9[P(CH3)2C6H5] (IVb) were also isolated from the reaction of lb with CS2. IVb has been analyzed crystallographically: space group P21/c, a = 10.001 (2) A,b= 13.523 (3) A, c = 18.660 (5) Å, β = 91.26 (2)°, Z = 4, Palla = 2.74 g/cm3. For 3404 reflections (F2 ≥ 3.0a(F)2) R = 0.058 and Fw = 0.067. IVb contains a thioformaldehyde ligand which is bonded to one osmium atom C-S = 1.79 (1) A while the sulfur atom simultaneously serves as a bridge across two osmium atoms. It also contains a triply-bridging inorganic sulfide ligand in a cluster of three osmium atoms which has only one osmium-osmium bond. When heated, both Illb and IVb decarbonylate to form the complex (µ3-η2-SCH2)(µ3-S)Os3(CO)8[P(CH3)2C6H5] (Vb). Vb was also analyzed crystallographically: space group Fl, at -35 °C, a = 9.103 (4) A, b = 11.722 (4) A, c = 11.819 (2) A, a = 71.87 (2)°, β = 79.66 (2), y = 82.20 (3)°, Z = 2, Palcd = 2.86 g/cm3. For 3668 reflections (F2 ≥ 3.0a(F)2) R = 0.037 and Rw = 0.041. Vb contains a triply-bridging thioformaldehyde ligand with the sulfur atom directly bridging two osmium atoms and the carbon atom bonded solely to the third. The C-S distance is 1.869 (6) A. Vb also contains a triply-bridging inorganic sulfide ligand, but unlike IVb the cluster has two osmium-osmium bonds. Mechanisms for the formation of all products are proposed and discussed. It was shown that dithioformato cluster complexes are not intermediates in the formation of Ila and lib as demonstrated by the inability of the complexes (m-S2CH)HOs3(CO)10 (IIIa), prepared by an independent method, and Illb to be converted into the dicluster complexes.