PROMOTION OF RING-OPENING NUCLEOPHILIC-ADDITION TO THIETANE LIGANDS BY THE BRIDGING COORDINATION OF THE SULFUR ATOM IN THE COMPLEXES OS3(CO)10[MU-SCH2CME2CH2] AND OS3(CO)10[MU-TRANS-SC(H)MECH2C(H)ME]

The reaction of Os3(CO)10[mu-activated SCH2CMe2CH2] (1) with the nucleophiles F-, Cl-, Br-, I-, EtO-, Et2NH, and (CH2)3NH at 25-degrees-C yielded after acidification the series of new complexes Os3(CO)10[mu-SCH2CMe2CH2X](mu-H) (X = F, 2, 27%; X = Cl, 3, 57%; X = Br, 4, 81%; X = I, 5, 90%; X = OEt, 6, 61%; X = NEt2, 7, 48%; X = N(CH2)3, 8, 68%). Complex 3 was characterized crystallographically and was found to contain a bridging chloroneopentanethiolato ligand formed by the ring-opening addition of chloride to one of the methylene groups of the thietane ligand. Each of the compounds 2-8 contains similarly derived thiolato ligands. The complex Os3(CO)10[mu-trans-activated SC(H)MeCH2C(H)Me] (9), an equimolar mixture of the 2R,4R and 2S,4S enantiomers, was found to undergo a ring-opening addition of I- to yield Os3(CO)10[mu-SC(H)MeCH2C-(H)Me(I)](mu-H) (10), an equimolar mixture of 2R,4S and 2S,4R enantiomers formed by an inversion of stereochemistry at the iodine-substituted carbon atom. The stereochemical inversion is consistent with the conventional backside nucleophilic addition mechanism. The reaction of the complex Os3(CO)11-[activated SCH2CMe2CH2] (11) with chloride yielded only the known anion [Os3(CO)11Cl]- by ligand displacement. Compounds 3 and 10 were characterized by single-crystal X-ray diffraction analyses. Crystal data: for 3, space group P2(1)/c, a = 11.841 (2) angstrom, b = 14.310 (3) angstrom, c = 14.642 (3) angstrom, beta = 100.91 (1)-degrees, Z = 4, 2263 reflections, R = 0.036; for 10, space group P1BAR, a = 12.534 (2) angstrom, b = 12.844 (3) angstrom, c = 7.587 (1) angstrom, alpha = 95.62 (2)-degrees, beta = 94.62 (1)-degrees, gamma = 89.24 (2)-degrees, Z = 2, 2680 reflections, R = 0.029.