NUCLEOPHILIC RING-OPENING OF BRIDGING THIETANE LIGANDS IN TRIRHENIUM CARBONYL CLUSTER COMPLEXES

The reactions of 3,3-dimethylthietane, SCH2CMe2CH2 (3,3-DMT), and thietane, SCH2CH2CH2, with Re3(CO)10(NCMe)2(mu-H)3, 1, have yielded the new complexes Re3(CO)10[mu-SCH2CMe2CH2](mu-H)3,2a, and Re3(CO)10[mu-SCH2CH2CH2](mu-H)3, 2b. Compound 2a was characterized crystallographically and was found to consist of a trirhenium cluster with three bridging hydride ligands and a bridging thietane ligand coordinated through its sulfur atom. 2a and 2b react with halide ions by ring-opening additions to the 3,3-DMT ligand to yield the complex anions [Re3(CO)10(mu-SCH2CMe2CH2X)(mu-H)3]-, 3a-6A X = F (71%), Cl (71%), Br (84%), I (87%), and (Re3(CO)10(mu-SCH2CH2CH2Cl)(mu-H)3]-, 4b (67%). Similarly, addition of NMes to 2a and 2b yielded the ring-opened zwitterions Res(CO)10(mu-SCH2CMe2CH2NMe3)(mu-H)3, 7a (43%), and Res(CO)10(mu-SCH2CH2CH2NMe3(u-H)3, 7b (44%). Compounds 4a and 7b were characterized crystallographically. They are zwitterions positively charged at the nitrogen atoms and negatively charged on the trirhenium clusters. Complex 7b was also obtained in a 48% yield from the reaction of Re3(CO)12(mu-H)3 with Me3NO in the presence of thietane, but the corresponding reaction using 3,3-DMT yielded only 2a and Re3(CO)11(SCH2CMe2CH2(mu-H)3, 8. Attempts to obtain a ring-opening addition to 2a by reaction with PMe2Ph yielded only Re3(CO)10(PMe2Ph)2(mu-H)3 by ligand substitution. Attempts to obtain ring-opening addition to 8 by reaction with I- yielded only (Re3(CO)11I(mu-H)3]- by ligand substitution. Crystal Data: for 2a, space group = C2/c, a = 15.749 (2) angstrom, b = 9.082 (2) angstrom, c = 31.799 (5) angstrom, beta = 99.17 (1)-degrees, Z = 8, 2325 reflections, R = 0.037; for 4a, space group = P1BAR, a = 13.140 (2) angstrom, b = 17.966 (4) angstrom, c = 12.252 (3) angstrom, alpha = 93.27 (2)-degrees, beta = 101.31 (2)-degrees, gamma = 74.90 (2)-degrees, Z = 2, 4495 reflections, R = 0.034; for 7b.0.5Me2C=O, space group = P2(1)/c, a = 8.475 (1) angstrom, b = 11.740 (5) angstrom, c = 26.085 (3) angstrom, beta = 93.74 (1)-degrees, Z = 4, 2234 reflections, R = 0.032.