CLUSTERS CONTAINING CARBENE LIGANDS .9. REACTION OF MEC=CNME2 WITH OS3(CO)10(MU-H)2

The reaction of Os3(CO)10(μ-H)2 with MeC≡CNMe2 at 25 °C yielded the new complex Os3(CO)10[μ-C-(Me)C(H)NMe2](μ-H) (1, 68%) by the addition and insertion of MeC≡CNMe2 into one of the metal-hydrogen bonds. Compound 1 contains a bridging C(Me)C(H)NMe2 ligand that is coordinated only by the methyl-substituted carbon atom. The hydride ligand was shifted to the NMe2-substituted carbon atom. When heated to 68 °C in hexane, 1 isomerized to the new complex Os3(CO)10[μ-CH(Me)CNMe2](μ-H) (2) by a shift of the hydrogen atom from the NMe2-substituted carbon atom to the methyl-substituted carbon atom. At 68 °C, 2 was slowly decarbonylated to yield the new compound Os3(CO)9(μ3-MeC2NMe2)(μ-H)2 (3), which contains a triply bridging MeC2NMe2 ligand. In a competing reaction 2 simultaneously isomerized to the new compound Os3(CO)10[μ-C(Et)N(Me)CH2](μ-H) (4), which contains an N-methyl-metalated ethyl(dimethylamino)carbene ligand that bridges an edge of the triosmium cluster. When heated to 97 °C for 36 h, 3 isomerized to the new compound Os3(CO)9[η3-CH(Me)C(H)NMe2](μ-H) (5), which exists in solution as a mixture of isomers. One of the isomers was crystallized and characterized structurally. It was shown to contain a triply bridging MeC(H)CNMe2 ligand. The carbon atoms of the alkenyl group are σ–π coordinated to an edge of the cluster, while the nitrogen atom is coordinated to the third metal atom. The ligand has Z stereochemistry. On the basis of NMR spectroscopy the other isomer is believed to contain a similarly coordinated ligand having E stereochemistry. Compounds 1-5 were all characterized by IR, NMR, and single-crystal X-ray diffraction analyses. Crystal data: for 1, space group P21/c, a = 8.842 (2) Å, b = 17.275 (8) Å, c = 14.211 (2) Å, β = 101.04 (1)°, Z = 4, 2211 reflections, R = 0.051, Rw = 0.053; for 2, space group P212121, a = 11.529 (2) Å, b = 17.829 (3) Å, c = 10.041 (1) Å, Z = 4,1849 reflections, R = 0.0298, Rw = 0.030; for 3, space group P21/c, a = 9.854 (1) Å, b = 15.517 (2) Å, c = 13.188 (2) Å, β = 92.09 (2)°, Z = 4, 2122 reflections, R = 0.037, Rw = 0.040; for 4, space group P1, a = 8.866 (2) Å, b = 15.310 (4) Å, c = 8.188 (2) Å, α = 103.12 (2)°, β = 105.38 (2)°, γ = 87.44 (2)°, Z = 2, 2497 reflections, R = 0.044, Rw = 0.050; for 5, space group C2/c, a = 17.241 (2) Å, b = 8.310 (1) Å, c = 26.767 (4) Å, β = 94.10 (1)°, Z = 8, 2298 reflections, R = 0.027, Rw = 0.028. © 1990, American Chemical Society. All rights reserved.