The synthesis and characterization of vanadium(III) and (IV) complexes with nitrogen and sulfur ligation

The reactivity of VCl{dollar}rmsb3(THF)sb3{dollar} with bipyridine and benzenethiolate has been investigated. The complexes (NEt{dollar}rmsb4)lbrack V(bpy)(SPh)sb4rbrack,{dollar} (NMe{dollar}rmsb4)lbrack V(bpy)(SPh)sb2(Cl)sb2rbrack,{dollar} (V(bpy){dollar}rmsb2(SPh)sb2rbrack(PFsb6),{dollar} and (V(Me{dollar}rmsb2bpy)sb2(SPh)sb2rbrack(PFsb6){dollar} have been synthesized and characterized by IR and UV/Vis spectroscopies, and elemental analysis, through variation of the bipyridine and thiolate ratios. The complex salt (V(bpy){dollar}rmsb2(SPh)sb2{dollar}) (V(bpy)(SPh){dollar}rmsb2(Cl)sb2{dollar}) was structurally characterized. In CH{dollar}rmsb2Clsb2{dollar} the anionic vanadium species undergo chloride for thiolate substitution and the complexes (NEt{dollar}sb4){dollar} (V(bpy)Cl{dollar}sb4{dollar}) and (PPh{dollar}rmsb4)lbrack V(bpy)Clsb4{dollar}) were obtained.; Reactivity studies on the mononuclear complexes showed them to be extremely sensitive to oxidation, yielding the complexes (NMe{dollar}rmsb4)lbrack VO(bpy)(SPh)sb3{dollar}), (NMe{dollar}rmsb4) lbrack VO(Mesb2bpy)(SPh)sb3{dollar}), and (VO(bpy){dollar}rmsb2(SPh)rbrack(PFsb6).{dollar} These species have been studied by IR, UV/Vis, and EPR spectroscopy. In addition the anionic vanadyl species have been crystallographically characterized. Hydrolysis of a solution of (NEt{dollar}sb4{dollar}) (V(Me{dollar}rmsb2bpy)(SPh)sb4{dollar}), generated in situ, formed the unique oxo-bridged compound V{dollar}rmsb2O(Mesb2bpy)sb2(SPh)sb4.{dollar} This complex was crystallographically characterized and found to contain a face-sharing bioctahedral arrangement of the two metals with two bridging thiolate ligands in addition to the bridging oxygen atom. Solid state and solution magnetic susceptibility studies indicate the presence of a V-V single bond and two strongly antiferromagnetically coupled electrons (J {dollar}> -{dollar}270 cm{dollar}sp{lcub}-1{rcub}{dollar}). Results of an extended Huckel calculation on the model complex V{dollar}rmsb2O(NHsb3)sb4(SPh)sb4{dollar} also support the presence of a V-V sigma bond.; Reactivity studies of (V(bpy){dollar}rmsb2(SPh)sb2rbrack(PFsb6){dollar} resulted in the isolation and structural characterization of the complexes (V(bpy){dollar}rmsb3rbrack (PFsb6)sb2{dollar}, (V{dollar}rmsb3Ssb7(bpy)sb3rbrack (PFsb6){dollar}, and (V{dollar}rmsb2O(bpy)sb4(SPh)sb2rbrack (PFsb6)sb2{dollar}. (V{dollar}rmsb3Ssb7(bpy)sb3rbracksp+{dollar} was found to be diamagnetic and extended Huckel calculations support the characterization of the complex as containing three delocalized vanadium-vanadium bonds. (V{dollar}rmsb2O(bpy)sb4(SPh)sb2rbracksp{lcub}2+{rcub}{dollar} contains a linear oxo-bridge. Variable temperature magnetic susceptibility studies indicated that the two metal centers are magnetically non-interacting. ({dollar}musb{lcub}rm eff{rcub}{dollar}/V=2.9{dollar}sb{lcub}rm mu B{rcub}).{dollar} The vanadium(II) complex was isolated as an impurity in the synthesis of the (V(bpy){dollar}rmsb2(SPh)sb2rbracksp+{dollar} starting material.; These compounds provide a set of model complexes for vanadium species which may be involved in the conversion of vanadyl impurities, found in heavy crude oils, to vanadium sulfide polymers during hydrodesulfurization. They support a possible route to polymer formation in which vanadyl species are reduced to vanadium(III) species, via the formation of (V-O-V) {dollar}sp{lcub}4+{rcub}{dollar} complexes, and then the vanadium(III) species subsequently incorporate sulfide ions and aggregate to form the (V{dollar}rmsb2Ssb3)sb{lcub}rm n{rcub}{dollar} polymers deposited on the HDS catalyst.