CLUSTERS CONTAINING CARBENE LIGANDS .10. TRANSFORMATION OF AN YNAMINE INTO AN AMINOCARBENE LIGAND BY UNSYMMETRIC HYDROGENATION WITH A TRIOSMIUM CLUSTER COMPLEX

The reaction of ynamine MeC2NMe2 with the lightly stabilized cluster complex Os3(CO)9(NCMe)(mu-OMe)(mu-H) (1) at 25-degrees-C yielded the product Os3(CO)9[mu-3-eta-3-MeC(H)CNMe2](mu-OMe)(mu-H) (2; 47%). Compound 2 was characterized crystallographically and was shown to consist of an open triosmium cluster with a triply bridging MeC(H)CNMe2 ligand formed by the transfer of the hydride ligand to the methyl-substituted carbon atom of the ynamine. A small amount of Os3(CO)10[mu-eta-2-MeC(H)CNMe2](mu-OMe) (3) was also obtained from this reaction. Compounds 2 and 3 can be interconverted by the addition and elimination of CO. Compound 3 contains an open triosmium cluster with a MeC(H)CNMe2 ligand bridging the two nonbonded metal atoms. Compound 2 was found to react with hydrogen at 80-degrees-C to yield two products, Os3(CO)8[mu-3-eta-3-MeC(H)CNMe2](mu-OMe)(mu-H)(H) (4; 35%) and Os3(CO)9[mu-3-eta-2-EtCNMe2](mu-OMe)(mu-H) (5; 15%). Compounds 4 and 5 were characterized crystallographically. 4 is similar to 2, but has one less CO ligand and two hydride ligands, one terminal and one bridge. 5 consists of an open cluster with a triply bridging ethyl(dimethylamino)carbene ligand. Compound 4 reacts with PMe2Ph to yield the complex Os3(CO)8(PMe2Ph)[mu-3-eta-2-MeC(H)CNMe2](mu-OMe)(mu-H)(H) (6; 66%), a simple PMe2Ph derivative of 4. 4 reacts with pyridine to yield Os3(CO)8(py)[mu-3EtCNMe2](mu-H) (7; 17%). Compound 7 was characterized crystallographically and was shown to be a pyridine derivative of 5. When CO was added to 7, it was converted to 5 in 96% yield. When heated to 125-degrees-C, 5 was isomerized to Os3(CO)9[C(Et)-NMe2](mu-OMe)(mu-H) (8) in 55% yield, which contains a closed triosmium cluster with a terminally coordinated ethyl(dimethylamino)carbene ligand. The net result is the unsymmetric hydrogenation of the ynamine, MeC2NMe2, to an ethyl(dimethylamino)carbene ligand. Crystal data are as follows: for 2, space group = P1BAR, a = 9.092 (1) angstrom, b = 14.751 (2) angstrom, c = 8.542 (1) angstrom, alpha = 97.28 (1)-degrees, beta = 115.302 (9)-degrees, gamma = 91.33 (1)-degrees, Z = 2, 2450 reflections, R = 0.021; for 3, space group = P2(1)/n, a = 10.041 (2) angstrom, b = 15.650 (3) angstrom, c = 14.135 (3) angstrom, beta = 113.109 (9)-degrees, Z = 4, 2509 reflections, R = 0.024; for 4, space group = P2(1)/c, a = 17.30 (1) angstrom, b = 15.165 (6) angstrom, c = 17.488 (8) angstrom, beta = 117.29 (3)-degrees, Z = 8, 2704 reflections, R = 0.061; for 5, space group = P2(1)/n, a = 12.354 (2) angstrom, b = 13.017 (2) angstrom, c = 13.371 (2) angstrom, beta = 96.10 (1)-degrees, Z = 4, 2143 reflections, R = 0.025; for 6, space group = P2(1)/c, a = 9.381 (1) angstrom, b = 11.653 (2) angstrom, c = 23.815 (8) angstrom, beta = 90.40 (2)-degrees, Z = 4, 2626 reflections, R = 0.037; for 7, space group = P1BAR, a = 9.498 (1) angstrom, b = 16.261 (3) angstrom, c = 8.828 (1) angstrom, alpha = 97.72 (2)-degrees, beta = 115.82 (3)-degrees, gamma = 78.61 (2)-degrees, Z = 2, 2760 reflections, R = 0.022; for 8, space group = P2(1)/n, a = 7.6725 (9) angstrom, b = 18.862 (3) angstrom, c = 15.250 (2) angstrom, beta = 100.15 (1)-degrees, Z = 4, 2426 reflections, R = 0.023.