Vanadium complexes with multidentate amine bisphenols

Area of Science:

• Coordination Chemistry
• Organometallic Chemistry
• Catalysis

Background:

• Vanadium complexes are versatile catalysts in oxidation reactions.
• Tripodal bisphenol ligands offer unique coordination environments for metal ions.
• Understanding the redox properties of vanadium complexes is crucial for catalytic applications.

Purpose of the Study:

• To synthesize and characterize novel vanadium(IV) and vanadium(V) complexes using tripodal bisphenol ligands.
• To investigate the electrochemical properties of the synthesized complexes.
• To evaluate the catalytic activity of vanadium(V) complexes in the epoxidation of cis-cyclooctene.

Main Methods:

• Reaction of vanadium precursors (VO(acac)2, VOSO4·5H2O, VO(OPr)3) with tripodal bisphenol ligands (H3L(1), H3L(2), H3L(3)).
• Characterization of the resulting vanadium complexes using spectroscopic and analytical techniques.
• Cyclic voltammetry (CV) to determine redox potentials.
• Catalytic epoxidation reactions using tert-BuOOH as the oxidant.

Main Results:

• Synthesis of a hexacoordinated vanadium(IV) complex [V(acac)(L(1))] (1).
• Formation of mononuclear oxovanadium(v) complexes [VO(L(2))] (2) and [VO(L(3))] (3) via oxidation.
• Complex 1 showed a reversible one-electron redox process at +1.18 V.
• Complexes 2 and 3 exhibited irreversible redox responses at -1.6 V and -1.2 V, respectively.
• Complexes 2 and 3 demonstrated moderate catalytic activity in cis-cyclooctene epoxidation.

Conclusions:

• Novel vanadium complexes with tripodal bisphenol ligands were successfully synthesized.
• The synthesized complexes display distinct redox behaviors dependent on the vanadium oxidation state and ligand environment.
• Vanadium(V) complexes 2 and 3 show promising catalytic activity for epoxidation, suggesting their utility in selective oxidation catalysis.