Synthesis of N(SiMe3)2 supported vanadium(III) complexes, including hydrocarbyl, tetrahydroborate and azaalkenylidene derivatives†
Abstract
Reaction of [(Me3Si)2N]2VCl(THF) (THF = tetrahydrofuran) with MgMe2 or LiMe afforded [(Me3Si)2N]2VMe(THF) in 70% yield. Nitrogen donors displaced THF in these VIII species, and [(Me3Si)2N]2VCl(lut) (lut = 3,5-dimethylpyridine) and [(Me3Si)2N]2VMe(pyr) (pyr = pyridine) were isolated and characterized. Solution thermolysis of [(Me3Si)2N]2VMe(THF) yielded the known VIII dimer {[(Me3Si)2N]V(µ-CH2SiMe2NSiMe3)}2 in 73% yield. Reaction of [(Me3Si)2N]2VMe(THF) with 3 equivalents of RNC (R = But or Xyl; Xyl = 2,6-dimethylphenyl) gave diazavanadacycles of empirical formulae [(Me3Si)2N]2V[(Me)(CNR)3]. For R = But, the product [(Me3Si)2N]2V[ButNCMeC(CNBut)NBut] features an exocyclic keteneamine functionality; for R = Xyl, an additional C–C bond forming step results in slightly more complex connectivity, to give [(Me3Si)2N]2V[N(Xyl)CMeC–C(NXyl)CMeCHCH–CHCMeC(N)]. The crystal structures of both compounds are presented. Alkylation of [(Me3Si)2N]2VCl(THF) with 2-thienyllithium led to isolation of [(Me3Si)2N]2V(2-C4H3S)(THF) (60%). A blue solution that acted as a source of ‘[(Me3Si)2N]2VPh’ was obtained from the reaction of 0.5 equivalent of MgPh2 with [(Me3Si)2N]2VCl(THF). The addition of pyr or PhCN to the blue mixture gave [(Me3Si)2N]2VPh(pyr) (60%) and [(Me3Si)2N]2V(NCPh2)(NCPh) (66%), respectively. The chelated aryl amine [(Me3Si)2N]2V(o-Me2NCH2C6H4) was synthesized from [(Me3Si)2N]2VCl(THF) and Li(o-Me2NCH2C6H4) in 81% yield. Treatment of [(Me3Si)2N]2VCl(THF) with excess LiBH4 in the presence of pyr afforded the vanadium tetrahydroborate [(Me3Si)2N]2V(η2-BH4)(THF) in 41% yield. The solid-state structures of [(Me3Si)2N]2VPh(pyr), [(Me3Si)2N]2V(NCPh2)(NCPh), [(Me3Si)2N]2V(η2-o-Me2NCH2C6H4) and [(Me3Si)2N]2V(η2-BH4)(pyr) are reported.