REACTIVITY STUDIES OF MONONUCLEAR AND DINUCLEAR VANADIUM SULFIDE THIOLATE COMPOUNDS

The synthesis, structure, and properties of (Me3NBz)2[V(S2)S2(SPh)] (1) and (Me3NBz)4[V2(S2)2(CS3)4] (2) are described. Compound 1 is produced via oxidation of V(III) by elemental sulfur in a reaction mixture comprising VCl3, LiSPh, S, and NEt4Cl in a molar ratio of 1:7:3:2. Compound 1 reacts with excess CS2 to produce compound 2 in ca. 65% yield. Compound 1 crystallizes in monoclinic space group P2(1)/n with the following unit cell dimensions at -158-degrees-C: a = 18.178 (8) angstrom, b = 8.843 (2) angstrom, c = 18.852 (7) angstrom, beta = 107.06 (2)degrees, and Z = 4. A total of 2807 unique reflections with F > 3.00sigma(F) were employed, and the structure solution was refined to conventional indices R and R(w) of 5.65 and 5.63, respectively. The vanadium(V) center is ligated by three types of sulfur atoms, viz. one PhS-, one persulfido (S2(2-)), and two sulfido (S2-); the coordination geometry is approximately tetrahedral, with the S2(2-) considered as occupying one site. Compound 2 crystallizes in monoclinic space group P2(1)/c with the following unit cell dimensions at -114-degrees-C: a = 20.978 (4) angstrom, b = 13.384 (2) angstrom, c = 21.613 (4) angstrom, beta = 93.14 (1)degrees, and Z = 4. A total of 5651 unique reflections with F > 2.33sigma(F) were employed, and the structure solution was refined to conventional R and R(w) indices of 6.32 and 6.75, respectively. The vanadium(IV) centers are bridged by two symmetry-related eta2:eta2:mu2-S2(2-) ligands, and two bidentate chelating trithiocarbonate ligands complete the coordination sphere about each metal. The metal centers are eight-coordinate, and the coordination geometry is best described as distorted dodecahedral. The V-V distances in the two independent molecules present in the unit cell are 2.872 (6) and 2.841 (6) angstrom, respectively, and the complex is diamagnetic. An EHMO calculation was performed in order to assess the extent of metal-metal bonding in 2. Comparisons with the more highly developed area of Mo/S chemistry are made. The terminal trithiocarbonate sulfur atoms of 2 are nucleophilic and can be alkylated with MeI to produce the neutral compound V2(S2)2(S2CSMe)4 (3) in high yield. Compound 3 reacts with secondary amines to form the dialkyldithiocarbamate compounds V2(S2)2(S2CNR2)4 (R = Et (4a); R = (n)Bu (4b)). Solution-phase H-1 and C-13 NMR studies of dimers 2-4 indicate the presence of two isomers whose interconversion is slow on the NMR time scale. Solution-phase V-51 NMR data are reported for compounds 1-4 and are compared to literature values for other V/S complexes.