CHARACTERIZATION OF THE OXO-ALKYLIDYNE COMPLEX CPWOS3(CO)10 (MU-O)(MU-3-CCH2TOL) RESULTING FROM ACYL LIGAND C-O BOND SCISSION - INTERCONVERSION OF ALKYLIDYNE, ALKYLIDENE, VINYLIDENE, AND ALKYNE LIGAND MOIETIES IN A SINGLE HETEROMETALLIC CLUSTER SYSTEM
Cleavage of the acyl C-0 bond in the mixed-metal cluster CPWOS3(CO)11[mu3-eta2-C(O)CH2-Tol] (1) (Cp = eta5-C5H5, Tol = p-C6H4CH3) is effected in refluxing toluene, with formation of the oxo-alkylidyne complex CPWOs3(CO)9(mu-0)(mu3-CCH2Tol)(3). Treatment of 3 with carbon monoxide (5 atm) in toluene at 110-degrees-C provides an adduct CpWOs3(CO)10(mu-0)(mu3-CCH2Tol) (2), which is an observable intermediate in the formation of 3. Complex 3 reacts with dihydrogen to afford a mixture of two isomeric hydrido-oxo-alkylidene complexes, CpWOs3(CO)9(mu-H)(mu-0)(mu-CHCH2Tol)(4a,b). A third isomer 4c is produced from a mixture of 4a and 4b either by thermolysis in boiling xylene or by treatment with hydrochloric acid. Pyrolysis of 3 in boiling toluene gives a hydrido-vinylidene complex CpWOs3(CO)9(mu-H) (mu-0) (mu-C=CHTol) (5), which undergoes further thermal reaction in boiling xylene to produce a hydrido-alkyne complex CpWOs3(CO)8(mu-H)(mu-O)(mu3-eta2-CHCTol)(6). Compounds 2, 3, 4a-c, 5, and 6 have been isolated as crystalline solids and characterized by spectroscopic (IR, MS, and H-1 and C-13 NMR) and analytical data. The structure of 2 has been determined by a single crystal X-ray diffraction study. Complex 2 crystallizes in the centrosymmetric monoclinic space group P2(1)/n with a = 9.988(1) angstrom, b = 17.673(2) angstrom, c = 15.940(2) angstrom, beta = 93.00(l)-degrees, V = 2809.9(6) angstrom3, and D(calc) = 2.91 g cm-3 for Z = 4 and molecular weight = 1232.83. The structure solution was refined to R(f) = 5.4% for all 3679 diffraction data (R(f) = 2.9% for those 2714 reflections with \F(o)\ > 6sigma(\F(o)\)). The WOs3 core of the molecule has a ''butterfly'' arrangement, with a dihedral angle of 138.4-degrees between the W-Os(2)-Os(l) and the W-Os(2)-Os(3) planes and bond lengths of W-Os(1) = 2.755-(1), W-Os(2) = 2.842(l), W-Os(3) = 2.710(l), Os(l)-Os(2) = 2.823(l), and Os(2)-Os(3) = 2.755(1) angstrom. An oxo ligand bridges the W-Os(l) bond, with W-0(1) = 1.801(8) and Os(1)-O-(1) = 2.137(8) angstrom; the angle W-0(1)-Os(1) = 88.4(3)-degrees. The mu3-alkylidyne ligand caps the W-Os(1)-Os(2) face, with W-C(1) = 1.97(l), Os(l)-C(l) = 2.20(1), and Os(2)-C(l) 2.18(1) angstrom.