Characterization of the Oxo-Alkylidyne Complex CpWOs₃(CO)₁₀(μ-O)(μ₃-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—O bond in the mixed-metal cluster CpWOs₃(CO)₁₁[μ₃-η²-C(O)CH₂-Tol] (1) (Cp = η⁵-C₅H₅, Tol = p-C₆H₄CH₃) is effected in refluxing toluene, with formation of the oxo–alkylidyne complex CpWOs₃(CO)₉(μ-O) (μ₃-CCH₂Tol) (3). Treatment of 3 with carbon monoxide (5 atm) in toluene at 110 °C provides an adduct CpWOs₃(CO)₉(μ-O)(μ₃-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(μ-H) (μ-O) (μ-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(μ-H) (μ-O) (μ-C=CHTol) (5), which undergoes further thermal reaction in boiling xylene to produce a hydrido—alkyne complex CpWOs₃(CO)₈(μ-H) (μ-O) (μ₃-η²-CHCTol) (6). Compounds 2,3,4a-c, 5, and 6 have been isolated as crystalline solids and characterized by spectroscopic (IR, MS, and ¹H and ¹³C 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 P2₁/n with a = 9.988(1) Å, b = 17.673(2) Å, c = 15.940(2) Å, β = 93.00(1)°, V = 2809.9(6) ų, 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| > 6σ(|F_o|)). The WOs₃ core of the molecule has a “butterfly” arrangement, with a dihedral angle of 138.4° between the W—Os(2)—Os(1) and the W—Os(2)—Os(3) planes and bond lengths of W—Os(1) = 2.755 (1), W—Os(2) = 2.842(1), W—Os(3) = 2.710(1), Os(1)—Os(2) = 2.823(1), and Os(2)—Os(3) = 2.755(1) Å. An oxo ligand bridges the W—Os(1) bond, with W—O(1) = 1.801(8) and Os(1)—O (1) = 2.137(8) Å; the angle W—O(1)—Os(1) = 88.4(3)°. The μ₃-alkaylidyne ligand caps the W—Os(1)—Os(2) face, with W—C(1) = 1.97(1), Os(1)—C(1) = 2.20(1), and Os(2)—C(1) = 2.18(1) Å.