THE ACTIVATION OF TERTIARY-AMINES BY OSMIUM CLUSTER COMPLEXES - FURTHER-STUDIES OF THE REACTION OF OS3(CO)10(NCME)2 WITH TRIETHYLAMINE

The reactions of Os3(CO)12 and Os3(CO)10(NCMe)2 with NEt3 have been reinvestigated. Two new products, Os3(CO)10(mu-CH2C(H) = NEt2)(mu-H) (2) and Os3(CO)10(syn-mu-eta-1-CHCHNEt2)(mu-H) (3) were obtained in low yields, 4% and 7%, in addition to the previously reported compound Os3(CO)10(anti-mu-eta-1-CHCHNEt2)(mu-H) (1) (20% yield) when the reaction was conducted at 25-degrees-C using Os3(CO)10(NCMe)2. Compounds 2 and 3 were characterized by IR, H-1 NMR and single-crystal X-ray diffraction analyses. Compound 2 contains a bridging methyl-metallated N-ethylimine ligand formed by the cleavage of one ethyl group from the NEt3. Compound 3 is an isomer of 1 in which the bridging ligand has a syn conformation with respect to the cluster as compared with the anti conformation in 1. Compound 3 slowly isomerizes to 1. Compound 3 is decarbonylated by exposure to UV radiation and is transformed to the new compound Os3(CO)9(mu-3-CC(H) = NEt2)(mu-H)2 (4) (58% yield) by an additional CH activation to form a triply bridging eta-1-diethylaminovinylidene ligand. Compound 4 isomerizes to the compound Os3(CO)9(mu-3-HCCNEt2)(mu-H)2 (5) (70% yield) at 68-degrees-C. The latter contains a triply briding ynamine ligand which exhibits structural and reactivity features that are characteristic of a carbene ligand at the amine-substituted carbon atom. Crystal data: for 2, space group = P2(1)/c, a = 9.236(2) angstrom, b = 12.469(2) angstrom, c = 18.107(3) angstrom, beta = 104.67(1)-degrees, Z = 4, 2518 reflections, R = 0.031; for 3, space group = P2(1)/m, a = 7.644(1) angstrom, b = 12.706(2) angstrom, c = 11.912(2) angstrom, beta = 108.02(1)-degrees, Z = 2, 1295 reflections, R = 0.030; for 4, space group = P2(1)/n, a = 10.233(2) angstrom, b = 14.834(4) angstrom, c = 14.538(2) angstrom, beta = 99.88(2)-degrees, Z = 4, 2403 reflections, R = 0.036.