Thermal degradation of HOs3(CO)10(μ-SCH2C6H5), I, at 150 °C leads to cleavage of the carbon-sulfur bond in the phenylmethanethiolato ligand by two competing processes. By one process the cleavage is followed by the elimination of toluene and the formation of the sulfidoosmium carbonyl clusters Os3-(CO)9(μ3-S)2, Os6(CO)16(μ4-S)(μ3-S), and Os7(CO)20(μ4-S)2. The second mechanism involves homolysis of the carbon-sulfur bond and formation of dibenzyl, the red hydride-containing hexanuclear cluster H2Os6(CO)17(μ4-S)(μ3-S), III, and its green isomer IV. Both III and IV were characterized by X-ray crystallographic methods. For III: space group C2/c, o = 20.364 (5) Å, b = 9.764 (4) Å, c = 32.544 (7) Å, β = 114.01 (2)°, V = 5900 (6) Å3, Z = 8, ρcalcd = 3.79 g/cm3. The structure was solved by direct methods (MULTAN) and refined (2456 reflections, F2≥ 3.0σ(F2)) to the final values of the residuals RF = 0.037 and RwF = 0.034. III contains two triosmium groupings linked by a quadruply bridging sulfido ligand and two metal-metal bonds. The quadruply bridging sulfido ligand has a highly distorted tetrahedral geometry with Os-S-Os bond angles ranging from 72.5 (1)° to 149.4 (2)°. III also contains a triply bridging sulfido ligand, two bridging hydride ligands, and 17 linear terminal carbonyl ligands. For IV: space group P21/n, a = 11.124 (3) Å, b = 14.090 (5) Å, c = 18.694 (7) Å, b = 92.00 (3)°, V = 2928 (3) Å3, Z = 4, ρcalcd = 3.82 g/cm3. The structure was solved by direct methods (MULTAN) and refined (2515 reflections, F2 ≥ 3.0σ(F2)) to final values of the residuals RF = 0.054 and RwF = 0.058. The structure of IV consists of a rhombus of four osmium atoms bridged on opposite sides by quadruply bridging and triply bridging sulfido ligands. Two adjacent edges of the rhombus contain bridging Os(CO)4 groups. The other two edges contain bridging hydride ligands. When exposed to UV radiation at room temperature, I undergoes facile homolysis of the carbon-sulfur bond and yields dibenzyl, compound III, and the new cluster H2Os6(CO)18(μ4-S)(μ3-S), V. For V: space group P1, a = 9.022 (2) Å,b- 11.986 (4) Å, c = 14.370 (3) Å, α = 89.94 (2)°, β = 78.23 (2)°, γ = 83.39 (3)°, V = 1511 (1) Å3, Z = 2, ρcalcd = 3.76 g/cm3. The structure was solved by the heavy-atom method and refined (3407 reflections, F2 ≥ 3.0σ-(F2)) to final values of the residuals RF = 0.044 and RwF = 0.044. Compound V is structurally similar to III. It contains two groups of three osmium atoms which are linked by a quadruply bridging sulfido ligand and one metal-metal bond which also contains a symmetrical bridging carbonyl ligand. The quadruply bridging sulfido ligand contains a highly distorted tetrahedral geometry, Os-S-Os angles range from 74.7 (1)° to 144.5 (2)°. In addition, there is a triply bridging sulfido ligand, two bridging hydride ligands, and 17 linear terminal carbonyl ligands. V can be converted into III both by thermolytic (68 °C) and photolytic decarbonylation.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry