Synthesis and characterization of vanadium(V) nitrido compounds: The role of ancillary ligands in determining structure and reactivity

Vanadium(V) silylimido compounds {dollar}rm V(NSiMesb3)Xsb3{dollar} (X = O-t-Bu (3a), O-i-Pr (4a), OPh (5a), {dollar}rm CHsb2SiMesb3{dollar} (6a), {dollar}rm NMesb2{dollar} (8a), O-2,6-Me{dollar}sb2{dollar}C{dollar}sb6{dollar}H{dollar}sb3{dollar} (11a), O-2,6-i-Pr{dollar}sb2{dollar}C{dollar}sb6{dollar}H{dollar}sb3{dollar} (11b), O-4-EtC{dollar}sb6{dollar}H{dollar}sb4{dollar} (11c), OCMe(CF{dollar}sb3)sb2{dollar} (22)) are prepared by the substitution of the chloride ligands of {dollar}rm V(NSiMesb3)Clsb3{dollar} (1). Reaction of 1 with {dollar}rm LiN(SiMesb3)sb2{dollar} affords {dollar}rm V(NSiMesb3)Clsb2lbrack N(SiMesb3)sb2rbrack.{dollar} Compound 8a is also prepared by the reaction of {dollar}rm V(NSiMesb3)(OSiMesb3)sb3{dollar} (2a) with {dollar}rm LiNMesb2.{dollar} Ligand exchange is observed in mixtures of 1 and 2a-8a affording {dollar}rm V(NSiMesb3)ClXsb2{dollar} and {dollar}rm V(NSiMesb3)Clsb2X.{dollar}; Compounds 2a-5a react with trans-{dollar}rm Ir(F)(CO)(PPhsb3)sb2{dollar} affording the nitrido-bridged complexes {dollar}rm (RO)sb3V{lcub}equiv{rcub}N{dollar}-Ir(CO)(PPh{dollar}sb3)sb2{dollar} (2d-5d). The rate of formation of 2d-5d varies with the purity and source of the starting materials, the identity of the ligands on 2a-5a, the solvent used and the addition of a soluble F{dollar}sp-{dollar} source, such as TASF, which catalyzes the reaction.; Substitution of the chloride ligands of {dollar}rm lbrack V(N)Clsb2(py)sb2rbrack sb{lcub}n{rcub}{dollar} (10) or the reaction of the silylimido compounds 5, 11, and 22 with substituted pyridines affords the vanadium(V) nitrido compounds {dollar}rm V(N)(OR)sb2Lsb2{dollar} (L = py, OR = OPh (12a), O-2,6-{dollar}rm Mesb2Csb6Hsb3{dollar} (13a), O-2,6-i-{dollar}rm Prsb2Csb6Hsb3{dollar} (13b), O-4-{dollar}rm EtCsb6Hsb4{dollar} (13c), {dollar}rm OCMe(CFsb3)sb2{dollar} (23a); L = 4-Etpy, OR = OPh (12b), {dollar}rm OCMe(CFsb3)sb2{dollar} (23b)). Dissociation of the py ligands of 12 and 13 affords oligomeric {dollar}rmlbrack V(N)(OR)sb2(py)rbrack sb{lcub}n{rcub}{dollar} and/or {dollar}rmlbrack V(N)(OR)sb2rbrack sb{lcub}n{rcub}.{dollar} This process is reversible and compounds 12 and 13 are readily recovered by addition of py to {dollar}rmlbrack V(N)(OR)sb2(py)rbrack sb{lcub}n{rcub}{dollar} and {dollar}rmlbrack V(N)(OR)sb2rbrack sb{lcub}n{rcub}.{dollar} An X-ray crystallographic study of dimeric (V({dollar}mu{dollar}-N)(O-2,6-{dollar}rm Mesb2Csb6Hsb3)sb2(py)rbrack sb2{dollar} reveals a nitrido bridged structure with a planar {dollar}rm Vsb2Nsb2{dollar} core and asymmetric V-N-V bridges (V = N = 1.725(2) A, V-N = 1.823(2) A). Vanadium(V) nitrido compounds with more stable, bidentate {dollar}rm Mesb2bipy{dollar} and TMEDA ligands have also been prepared.; Anionic nitrido compounds {dollar}rm Mlbrack V(N)(OR)sb3rbrack lbrack M = Na, OR = OCMe(CFsb3)sb2;{dollar} M = Li, OR = OPh, O-4-{dollar}rm EtCsb6Hsb4,{dollar} O-2,6-{dollar}rm Mesb2Csb6Hsb3,{dollar} O-2,6-i-{dollar}rm Prsb2Csb6Hsb3{dollar} (20c)) are prepared by the reaction of the silylimido compounds with lithium or sodium alkoxides or aryloxides or by the substitution of the chloride ligands of {dollar}rm lbrack V(N)Clsb2(py)sb2rbrack sb{lcub}n{rcub}.{dollar}; Compounds 20c and 23a react cleanly with electrophiles such as XSiMe{dollar}sb3{dollar} affording substitution across the V-N bonds of these compounds.