title: Metal effects on ligand non-innocence in Group 5 complexes of the redox-active [ONO] pincer ligand.
abstract: Isostructural vanadium, niobium and tantalum complexes of bis(3,5-di-tert-butyl-2-phenol)amine ([ONO]H3), were prepared and characterized to evaluate the impact of the metal ion on redox-activity of the ligand platform. New vanadium and niobium complexes with the general formula, [ONO]MCl2L (M = V, L = THF, 1-V; M = Nb, L = Et2O, 1-Nb) were prepared and structurally analysed by X-ray crystallography. The solid-state structures indicate that the niobium derivative is electronically analogous to the tantalum analog 1-Ta, containing a reduced (ONO) ligand and a niobium(V) metal ion, [ONO(cat)]Nb(V)Cl2(OEt2); whereas, the vanadium derivative is best described as a vanadium(IV) complex, [ONO(sq)]V(IV)Cl2(THF). One-electron oxidation was carried out on all three metal complexes to afford [ONO]MCl3 derivatives (3-V, 3-Nb, 3-Ta). For all three derivatives, oxidation occurs at the (ONO) ligand. In the cases of niobium and tantalum, electronically similar complexes characterized as [ONO(sq)]M(V)Cl3 were obtained and for vanadium, ligand-based oxidation led to the formation of a complex best described as [ONO(q)]V(IV)Cl3. All complexes were characterized by spectroscopic and electrochemical methods. DFT and TD-DFT calculations were used to probe the electronic structure of the complexes and help verify the different electronic structures stemming from changes to the coordinated metal ion.
authors.affiliation: Department of Chemistry, 1102 Natural Sciences 2, University of California, Irvine, CA 92697-2025, USA. aheyduk@uci.edu filipp.furche@uci.edu.
authors.forename: Steven
authors.initials: S
authors.lastname: Hananouchi
authors.forename: Brandon T
authors.initials: BT
authors.lastname: Krull
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Ziller
authors.forename: Filipp
authors.initials: F
authors.lastname: Furche
authors.forename: Alan F
authors.initials: AF
authors.lastname: Heyduk