THERMAL AND PHOTOASSISTED RING-OPENING OF THIETANE IN A TRIOSMIUM CLUSTER COMPLEX

UV irradiation of Os3(CO)11[S(CH2)31, 1, produced decarbonylation and formation of two isomers, Os3(CO)10[mu-S(CH2)2CH2], 2, and Os3(CO)10[mu-SCH2CH=CH2](mu-H), 3, by C-S bond cleavage and opening of the thietane ring. Compound 2 contains a thiametallacyclopentane ring system that was formed by insertion of an osmium atom into one of the C-S bonds. Compound 3 contains a 2-propenethiolato ligand and bridging hydride ligand formed by a combination of C-S and C-H bond cleavage at the 3-position of the thietane ligand. When heated to 97-degrees-C, 2 was converted to 3 by a beta-elimination reaction and Os2(CO)6[mu-SCH2CH2CH](mu-H), 4, by a fragmentation of the cluster. Compound 4 has only two metal atoms, and these are bridged by the sulfur atom, a hydride ligand, and an alkylidene carbon. Compound 3 was also formed in the reaction of thietane with Os3(CO)10(NCMe)2 at 25-degrees-C. Compound 2 adds phosphines by opening the cluster to yield the adducts Os3(CO)10[mu-S(CH2)2](L) (5, L = PPh3; 6, L = PMe2Ph). At 97-degrees-C, 5 and 6 undergo beta-elimination involving the metallacycle to yield the complexes Os3(CO)9[mu-SCH2CH=CH2] (L)(mu-H) (7, L = PPh3; 8, L = PMe2Ph) which are simply phosphine-substitution derivatives of 2. Compounds 1, 2, 4, 6, and 7 were characterized by single-crystal X-ray diffraction analysis. For 1: space group P2(1)/c, a = 9.020 (2) angstrom, b = 11.673 (3) angstrom, c = 19.7000 (4) angstrom, beta = 94.21 (2)-degrees, Z = 4, 1947 reflections, R = 0.038. For 2: space group P2(1), a = 11.750 (3) angstrom, b = 12.623 (2) angstrom, c = 13.242 (5) angstrom, beta = 100.79 (2)-degrees, Z = 4, 2423 reflections, R = 0.055. For 4: space group P1BAR, a = 8.5830 (9) angstrom, b = 12.999 (2) angstrom, c = 6.4810 (6) angstrom, alpha = 92.23 (1)-degrees, beta = 110.370 (8)-degrees, gamma = 74.165 (9)-degrees, Z = 2, 1266 reflections, R = 0.027. For 6: space group P2(1)/n, a = 10.536 (2) angstrom, b = 18.131 (3) angstrom, c = 14.174 (2) angstrom, beta = 99.57 (1)-degrees, Z = 4, 2780 reflections, R = 0.024. For 7: space group = P1BAR, a = 10.341 (1) angstrom, b = 17.584 (4) angstrom, c = 9.736 (2) angstrom, alpha = 98.35 (2)-degrees, beta = 93.14 (1)-degrees, gamma = 84.39 (2)-degrees, Z = 2, 3247 reflections, R = 0.038.