Characterization and structures of intermediates in the reactivity of CpWOs₃(CO)₁₁(μ₃-CTol) towards dihydrogen and water

Initial decarbonylation of CpWOs₃(CO) ₁₁(μ₃-CTol) (1; Cp = η⁵-C₅H₅, Tol = p-C₆H₄Me) with Me₃NO/MeCN followed by reaction with dihydrogen and water produces a dihydrido complex CpWOs₃(CO)₁₀(μ₃-CTol)(μ-H)₂ (2), a 'butterfly' cluster with a 60 valence electron (VE), and an oxo complex CpWOs₃(CO) ₁₀(μ-O)(μ₃-CTol) (4) respectively. Complex 2 reacts either with carbon monoxide to produce the starting alkylidyne complex 1 by reductive elimination of dihydrogen or with PPh₃ to afford a 62 VE 'butterfly' complex CpWOs₃(CO) ₁₀(PPh₃)(μ₃-CTol)(μ-H)₂ (6). Thermolysis of 2 in the presence of water gives a hydrido oxo alkylidene complex, syn-CpWOs₃(CO)₉(μ-O)(μ-CHTol)(μ,-H) (3a), in which the tolyl substituent on the alkylidene carbon is oriented syn to the μ-oxo ligand. Thermolysis of 4 at 110°C induces decarbonylation to give a tetrahedral alkylidyne complex CpWOs₃(CO)₉(μ-O)(μ3-CTol) (5), which is reversibly converted back to 4 upon exposure to carbon monoxide. Complex 5 reacts with dihydrogen to afford a mixture of two isomeric hydrido oxo alkylidene complexes, anti-CpWOs₃(CO)₉(μ-O)(μ-CHTol)(μ-H) (3b,c). The syn-isomer 3a is also produced from a mixture of 3b and 3c by thermolysis in boiling toluene. Compounds 2, 3a,b,c, 4, 5 and 6 have been isolated as crystalline solids and characterized by spectroscopic (IR, MS, ¹H and ¹³C NMR) and analytical data. The structures of 2 and 6 have been determined by single crystal X-ray diffraction studies. Compound 2 crystallizes in the orthorhombic space group P2₁2₁2₁ with unit cell parameters a = 14.18(1), b = 28.46(1), c = 13.59(3) Å, V = 5484(13) Å3 and Z = 8. Compound 6 crystallizes in the monoclinic space group P2₁/n with unit cell parameters a = 19.298(2), b = 22.406(4), c = 9.364(1) Å, β = 92.83(9)°, V = 4044.0(9) Å3 and Z = 4. Diffraction data were collected on a CAD4 diffractometer, and structures were refined to R = 0.0957 and 0.0510 for 2 and 6 respectively. Both 2 and 6 are based upon a 'butterfly' WOs₃ metal core with a respective dihedral angle of 114.3(2)° and 113.6(4)° between the W-Os(2)-Os(1) and W-Os(2)-Os(3) planes. Each molecule consists of three Os(CO)₃ units and a CpW(CO) fragment, except that the Os(1) center in 6 is additionally coordinated with PPh₃. The μ3-alkylidyne caps unsymmetrically the respective W-Os(2)-Os(3) face of both complexes.