Reactions of (Arylimido)vanadium(V)-Trialkyl Complexes with Phenols: Effects of Arylimido Ligands and Phenols for Formation of the Vanadium Phenoxides.

ABSTRACT: Reactions of a series of (arylimido)vanadium(V) trialkyl complexes, V(NAr')(CH₂SiMe₃)₃ (Ar' = C₆H₅, 2-MeC₆H₄, 2,6-Me₂C₆H₃, 2,6-Cl₂C₆H₃), with various phenols (ArOH, Ar = 2,6-F₂C₆H₃, 2,6-Cl₂C₆H₃, 2,6-Me₂C₆H₃, 2,6- ⁱ Pr₂C₆H₃, 2- ^t BuC₆H₄, 2,6- ^t Bu₂C₆H₃; 1.0 equiv) affording V(NAr')(CH₂SiMe₃)₂(OAr) were conducted in C₆D₆ at 25 °C, and the effects of both arylimido ligands and phenols on the substitution rate were explored. Sterically hindered arylimido ligands showed lower reactivity, and the reaction proceeded in the order: Ar' = 2,6-Me₂C₆H₃ < 2,6-Cl₂C₆H₃ < 2-MeC₆H₄ < C₆H₅. This order is somewhat different from that obtained from the chemical shifts in V(NAr')(CH₂SiMe₃)₃ in the ⁵¹V NMR spectra. The conversions with various disubstituted phenols increased in the order: 2,6- ⁱ Pr₂C₆H₃OH < 2,6-Me₂C₆H₃OH < 2,6-Cl₂C₆H₃OH < 2,6-F₂C₆H₃OH, irrespective of the kind of arylimido ligands. The reactions of V(NAr')(CH₂SiMe₃)₃ with 2,6- ^t Bu₂C₆H₃OH (1.0 or 3.0 equiv) did not take place even upon heating at 60 °C. These results suggest that the reactions proceed via coordination of ArOH toward vanadium, and the reactivity is highly dependent on steric bulk of both the arylimido ligand and the phenol.

SUBMITTER: Hayashibara H 

PROVIDER: S-EPMC6648231 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature