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  • Metal effects on ligand non-innocence in Group 5 complexes of the redox-active [ONO] pincer ligand.

Metal effects on ligand non-innocence in Group 5 complexes of the redox-active [ONO] pincer ligand.

Dalton transactions (Cambridge, England : 2003) (2014-10-30)
Steven Hananouchi, Brandon T Krull, Joseph W Ziller, Filipp Furche, Alan F Heyduk
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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Tetrabutylammonium hexafluorophosphate, 98%
Sigma-Aldrich
Ferrocene, 98%
Sigma-Aldrich
Tetrabutylammonium hexafluorophosphate, purum, ≥98.0% (CHN)
Supelco
Tetrabutylammonium hexafluorophosphate, for electrochemical analysis, ≥99.0%