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Coordination and scission of alkynes on a tungsten-triosmium framework. Crystal structures of (η5-C5H5)WOs3(CO) 10[μ3η2-C2(C 6H4CH3)2]H and (η5-C5H5)WOs3(CO) ...
Park, Joon T.,Shapley, John R.,Bueno, Clifford,Ziller, Joseph W.,Churchill, Melvyn Rowen
, p. 2307 - 2316 (2008/10/08)
Full title: Coordination and scission of alkynes on a tungsten-triosmium framework. Crystal structures of (η5-C5H5)WOs3(CO) 10[μ3η2-C2(C 6H4CH3)2]H and (η5-C5H5)WOs3(CO) 10[μ3-η2-C2(CO 2C2H5)2]H - species with an alkyne ligand bound to Os3 and WOs2 faces of tetrahedral WOs3 clusters. Reactions of CpWOs3(CO)12H (Cp = η5-C5H5) with various alkynes (RC≡CR′) produce two isomeric (symmetrical and/or unsymmetrical) alkyne complexes CpWOs3(CO)10(μ3-η2-C 2RR′)H [R = R′ = H, Ph, Tol, CF3, CO2Et; R = Ph, R′ = Tol; R = Ph, R′ = CO2Et] (Ph = C6H5, Tol = p-C6H4CH3) depending on the substituents R and R′ of alkynes. Some of the symmetrical isomers (R = CF3, CO2Et) undergo irreversible thermal isomerization to the unsymmetrical isomers. The diarylalkyne complexes (R = R′ = Ph, Tol; R = Ph, R′ = Tol) undergo facile intramolecular C≡C bond scission reactions after CO loss by Me3NO to yield the corresponding dialkylidyne clusters CpWOs3(CO)9(μ3-CR)(μ 3-CR′)H in ca. 60% yield along with alkyne-oxo clusters CpWOs3(CO)8(μ-O)(μ3-η 2-C2RR′)H in ca. 10% yield. The isomeric alkyne complexes, alkyne-oxo clusters, and dialkylidyne clusters have been isolated as crystalline solids and have been characterized by spectroscopic (infrared, mass, 1H and 13C NMR) data. CpWOs3(CO)10(μ3-η2-C 2Tol2)H crystallizes in the centrosymmetric monoclinic space group P21/n (No. 14) with a = 23.600 (5) A?, b = 9.343 (2) A?, c = 28.774 (4) A?, β = 97.39 (2)°, V = 6292 (2) A?3, and Z = 8. The structure solution converged with RF = 5.0% for those 4223 reflections with |F0| > 3.0σ(|F0|) and RF = 8.6% for all 5816 independent data (Mo Kα?, 2θ = 4.5-40.0°). There are two essentially equivalent molecules in the crystallographic asymmetric unit. Each consists of a tetrahedral WOs3 cluster in which the C2Tol2 ligand is bound to an Os3 face (π-bonded to Os(3) and σ-bonded to Os(1) and Os(2)). Os(3) bears two terminal carbonyl ligands, while Os(1) and Os(2) each have three. The W atom has two CO ligands, one of which is involved in a semibridging manner with the otherwise electron-poor Os(3); the hydride ligand (not located directly) is believed to span the Os(1)-Os(2) linkage. CpWOs3(CO)10(μ3-η2-C 2(CO2Et)2)H crystallizes in the centrosymmetric triclinic space group P1 (No. 2) with a = 9.121 (4) A?, b = 9.964 (3) A?, c = 15.729 (4) A?, α = 85.63 (2)°, β= 83.30 (3)°, γ = 85.74 (3)°, V = 1412.5 (8) A?3, and Z = 2. Refinement converged with RF = 4.87% for those 4240 data with |F0| > 3.0σ(|F0|) and RF = 5.55% for all 4868 independent data (Mo Kα?, 2θ = 4.5-50.0°). The molecule contains a tetrahedral WOs3 cluster, with the C2(CO2Et)2 ligand now bound to a WOs2 face (π-bonded to W and σ-bonded to Os(1) and Os(3)). The Os atoms each bear three terminal CO ligands, while the W atom has only one.
