CYCLOBUTYNE LIGANDS .1. SYNTHESIS AND REACTIVITY OF A CYCLOBUTYNE LIGAND IN A TRIOSMIUM COMPLEX, INCLUDING A STRUCTURAL CHARACTERIZATION OF THE 1ST CYCLOBUTYNE LIGAND IN THE COMPLEX OS3(CO)9(MU-3-ETA-2-C2CH2CH2)(MU-SPH)(MU-H)

The reaction of the triosmium complex Os3(CO)10(NCMe)2 with 1-(phenylthio)cyclobutene, PhSC = CHCH2CH2, at 25-degrees-C resulted in the formation of the two products Os3(CO)10(mu-eta2-C = CHCH2CH2)(mu-SPh) (1) and Os2(CO)6(mu-eta2-C=CHCH2CH2)(mu-SPh) (2) by the addition of the 1-(phenylthio)cyclobutene and cleavage of the carbon-sulfur bond to the cyclobutenyl group. The formation of 2 involved in addition a partial degradation of the metal cluster. Both products were characterized by X-ray diffraction analysis, and both complexes were found to contain a mu-eta2-cyclobutenyl ligand bridging two metal atoms. When treated with Me3NO in a refluxing CH2Cl2 solution, compound 1 was converted to 2 (21 % yield) and the new complex Os3(CO)9(mu-eta2-2CH2CH2)(mu-SPh)(mu-H), 3 (35 % yield). Complex 3 was characterized by X-ray diffraction analysis and was found to contain a triply bridging cyclobutyne ligand formed by the cleavage of the alkenyl C-H bond in the cyclobutenyl ligand and the transfer of the hydrogen atom to the metal atoms. When heated to 125-degrees-C, compound 3 was transformed into two new products: Os2(CO)6(mu-C2CH2CH2C6H4S) (4) (36 %) and Os3(CO)8[mu3-SC6H4CCHC(H)Me] (mu-H) (5) (10 %). For comparisons, the compound Os3(CO)9(mu-eta2-MeC2Me) (mu-SPh) (mu-H) (6) was also synthesized. All six compounds 1-6 were structurally characterized by single-crystal X-ray diffraction analysis. The C-C triple bond in 3 is coordinated to three metal atoms in the classical mu3-eta2 mode. The length of the coordinated triple bond in 3 is 1.37(2) angstrom. In 6 it is slightly longer at 1.42(2) angstrom. In compound 4 the cyclobutyne ligand was coupled to the thiolate phenyl group at an ortho position and the cluster was reduced to two metals. Compound 5 contains a metalated methylallyl group that is also coupled to the thiolate phenyl group at an ortho position. The allyl grouping in 5 was apparently formed by a ring-opening transformation of the the cyclobutyne ligand. Crystal data: for 1, space group = P2(1), a = 13.638(2) angstrom, b = 17.582(4) angstrom, c = 9.946(2) angstrom, beta = 93.01(2)-degrees, Z = 4,3264 reflections, R = 0.046; for 2, space group = P1BAR, a = 9.565(2) angstrom, b = 12.388(2) angstrom, c = 7.951(2) angstrom, alpha = 102.74(1)-degrees, beta = 98.85(1)-degrees, gamma = 85.23(1)-degrees, Z = 2,1836 reflections, R = 0.034; for 3, space group P2(1)/n, a = 10.954(2) angstrom, b = 16.540(3) angstrom, c = 12.495(2) angstrom, beta = 91.98(2)-degrees, Z = 4, 2233 reflections, R = 0.033; for 4, space group = P1BAR, a = 14.432(2) angstrom, b = 16.057(3) angstrom, c = 7.787(2) angstrom, alpha = 90.85(2)-degrees, beta = 93.20(1)-degrees, gamma = 77.47(1)-degrees, Z = 4, 2678 reflections, R = 0.044; for 5, space group = P1BAR, a = 14.109(3) angstrom, b = 14.542(4) angstrom, c = 11.509(4) angstrom, alpha = 105.98(2)-degrees, beta = 106.44(2)-degrees, gamma = 92.51(2)-degrees, Z = 4, 2744 reflections, R = 0.045; for 6, space group = P2(1)/n, a = 11.008(2) angstrom, b = 16.759(2) angstrom, c = 12.560(2) angstrom, beta = 91.45(1)-degrees, Z = 4, 2773 reflections, R = 0.038.