tert-Butylimido complexes of chromium and vanadium. X-Ray crystal structures of Cr(NBut)Cl3(MeOCH2CH2OMe), Cr[C6H4(NH)2-o]Cl2(PMe2Ph)2, Cr(NBut)2(OSiPh3)2, Cr(NBut)-Cl(OC9H6N)2 and [(PPh3)2][Cr(NBut){S2C2(CN)2}2]

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Abstract
The compound Cr(NBut)Cl3, isolated as its adducts with tetrahydrofuran (thf) and 1,2-dimethoxyethane (dme), has been prepared by chlorination of Cr(NBut)2Cl2. These materials have been used as sources of other chromium compounds such as the neutral adducts Cr(NBut)Cl3(PR3)2(R3= Me3, Et3, Me2Ph or EtPh2) or Cr(NBut)Cl2(NC7H13)(NC7H13= quinuclidine) or anionic complexes such as [PPh4][Cr(NBut)Cl4]. The tertiary phosphine complexes in the presence of excess of phosphine are photochemically or thermally reduced to CrCl3(PR3)3 and the tertiary phosphinimine. Halide-substitution reactions on Cr(NBut)Cl3(dme) or [Cr(NBut)Cl4]– with O,N, (O,N) and S ligands give rise to compounds such as cis-Cr(NBut)Cl(OC9H6N)2(OC9H6N = quinolin-8-olate), [Cr(NBut)(mnt)2]–(mnt = maleonitriledithiolate) and Cr(NBut)Cl(S2CNEt2)2; cyclic voltammetry of the last two complexes is reported. Evidence for the disproportionation 2CrV→ CrVI+ CrIV in reactions of alkoxides is given. Reduction of Cr(NBut)Cl3(dme) in the presence of 1,2-bis(dimethylphosphino)ethane (dmpe) gives the chromium(IV) species [Cr(NBut)(dmpe)2Cl]Cl. The EPR (X-band) spectra of chromium(V) species at room temperature show hyperfine splitting for 53Cr, 14N and 31P in appropriate compounds with giso values at 77 K of ca. 2.00. The compounds [V(NBut)(NHBut)(µ-NBut)]2 and [V(µ-NBut)(OSiMe3)2]2 are also described. The X-ray structures of five compounds have been determined: Cr(NBut)Cl3(dme) is octahedral with a mer arrangement of the three chlorines; Cr[C6H4(NH)2-o]Cl2(PMe2Ph)2 is also octahedral, having C2 symmetry with trans phosphines and cis chlorines; Cr(NBut)2(OSiPh3)2 is distorted tetrahedral; Cr(NBut)Cl(OC9H6N)2 is octahedral with the chelating quinolin-8-olato groups arranged to give trans O,O and cis N,N geometry; and [Cr(NBut)(mnt)2]– has a square-pyramidal structure with an axial imido group.

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