C-S BOND-CLEAVAGE IN TRIS(MU-THIOETHER)DITUNGSTEN(III) COMPLEXES IN REACTIONS WITH ANIONIC NUCLEOPHILES, INCLUDING HYDRIDE - SYNTHESIS AND STRUCTURE OF [PPH4][CL3W(MU-THT)2(MU-S(CH2)4CL)WCL3] AND NA[CL3W(MU-SET2)2(MU-SET)WCL3].3THF

The bridging thioether ligands in the complexes Cl3W(mu-Et2S)3WCl3 (1) and Cl3W(mu-THT)3WCl3 (2) (THT = tetrhydrothiophene) are highly susceptible to nucleophilic attack by the anions X- (X = SR-,SeR-,Cl-,Br-,H-), resulting in the cleavage of a C-S bond. Attack on 1 yields complexes containing the deethylated anion [Cl3W(mu-SEt)(mu-SEt)(mu-SEt2)2WCl3]-, and the byproducts EtX. Nucleophilic attack on the THT in 2 results in ring opening to give functionalized mu-thiolate anions of general formula [Cl3W(mu-THT)2(mu-S(CH2)4X)WCl3]-. The yields of these derivatives are essentially quantitative. Crystal structures of two representative derivatives are reported. Na[Cl3W(mu-SEt)(mu-SEt2)2WCl3].3THF (3a) crystallizes in the triclinic space group P1BAR with a = 11.306 (1) angstrom, b = 12.750 (1) angstrom, c = 14.936 (1) angstrom, alpha = 91.990 (9)-degrees, beta = 105.180 (8)-degrees, gamma = 114.530 (8)-degrees, V = 1865.0 (4) angstrom 3, Z = 2, d(c) = 1.890 g/cm3, mu-(Mo K-alpha) = 69.24 cm-1, R = 0.061, and R(w) = 0.079 for 274 parameters and 6229 unique data having F > 4.0-sigma-(F). [PPh4][Cl3W(mu-THT)2(mu-S(CH2)4Cl)WCl3] (4) crystallizes in the monoclinic space group P2(1)/n with a = 8.952 (3), b = 18.136 (5), c = 26.525 (5) angstrom, beta = 94.43 (2)-degrees, V = 4293.56 angstrom 3, Z = 4, d(c) = 1.887 g/cm3, mu-(Mo K-alpha) = 58.5 cm-1, R = 0.040, and R(w) = 0.045 for 433 parameters and 5956 unique data having I > 3-sigma-(I). The anions in both 3a and 4 have a confacial bioctahedral framework in which one of the mu-thioether ligands in the precursor complexes has been converted to a mu-thiolate. The reaction between hydride and 1 or 2 is a possible model for hydrodesulfurization.