CYCLOBUTYNE LIGANDS .3. SYNTHESIS AND CHARACTERIZATION OF A DISUBSTITUTED CYCLOBUTYNE LIGAND IN THE TRIOSMIUM COMPLEX OS3(CO)9[(MU(3)-ETA(2)-C2CH2C(ME)TBU)]MU(3)-S)

The reaction of 4-tert-butyl-4-methyl-1-(phenylthio)cyclobutene with Os3(CO)10(NCMe)2 at 25-degrees-C yielded the new complex Os3(CO)10[mu-PhSC2CH2C(Me)tBu](mu-H), 3 (54% yield), by displacement of the MeCN ligands and the addition of the 4-tert-butyl-4-methyl-1-(phenylthio)-cyclobutene and the activation of the alkenyl CH bond. Compound 3 was decarbonylated by refluxing in heptane solvent (97-degrees-C) to yield the new compound Os3(CO)9[mu3-SPhC2CH2C(Me)tBu](mu-H), 4 (93%), in which the alkenyl double bond of the metalated cyclobutenyl ligand has become coordinated to the cluster. When heated to 125-degrees-C, compound 4 was transformed to the new complex Os3(CO)9(mu3-eta2-C2CH2C(Me)tBu)(mu3-S), 5 (60% yield based on 4 consumed). Compound 5 contains a triply bridging 3-methyl-3-tert-butylcyclobutyne ligand formed from the metalated cyclobutenyl ligand by cleavage from the sulfur atom in 4. The phenyl group was also cleaved from the sulfur atom, resulting in the formation of a triply bridging sulfido ligand. The phenyl group and hydride ligand were eliminated, presumably as benzene. The C-C triple bond in 5 is coordinated to three metal atoms in the mu3-eta2 mode. The length of the coordinated triple bond in 5 is 1.40(2) angstrom. All three products were characterized by single crystal X-ray diffraction analysis. Crystal data: (for 3) space group = P2(1)/c,a = 7.764(1) angstrom, b = 17.722(4) angstrom, c = 21.153(3) angstrom, beta = 92.36(1)degrees, Z = 4, 2451 reflections, R = 0.023; (for 4) space group = P1BAR, a = 11.845(2) angstrom, b = 13.196(3) angstrom, c = 9.840(2) angstrom, alpha = 99.33(2)degrees, beta = 113.71(1)degrees, gamma = 85.73(1)degrees, Z = 2, 2782 reflections, R = 0.024; (for 5) space group = P2(1)/c, a = 9.178(1) angstrom, b = 17.913(4) angstrom, c = 14.329(2) angstrom, beta = 93.904(9)degrees, Z = 4, 2157 reflections, R = 0.025.