An oxorhenium(V) Schiff-base complex: synthesis, structure, spectroscopic characterization, electrochemistry, and DFT calculations

Abstract

Reaction of the Schiff base 2-[(2-hydroxyethylimino)methyl]phenol (H₂L) with trans-ReOCl₃(PPh₃)₂ in 1 : 1 M ratio in dichloromethane gives [ReOCl₂(HL)(PPh₃)] (1) in substantial yield. The compound has been characterized by C, H, and N microanalyses, IR, UV-Vis, ¹H NMR, and ESI-MS spectra. The X-ray crystal structure of the title compound has been determined. The structure reveals that it is an octahedral cis-Cl, Cl oxorhenium(V) complex where the relative positions of the two chlorides are cis. 1 crystallizes in the monoclinic space group P2₁/n with a = 14.198(2), b = 10.970(1), c = 18.258(1) Å, β = 111.83(1)°, V = 2640.0(3) ų, and Z = 4. Electrochemical studies in dichloromethane show Re(V) to Re(VI) oxidation at 1.51 V along with two successive reductions – Re(V) to Re(IV) and Re(IV) to Re(III) at −0.66 V and −1.03 V versus Ag/AgCl, respectively. Geometry optimization of 1 vis-à-vis its trans analog, trans-Cl, Cl complex 2, has been performed at the level of density functional theory; 2 is more stable than 1 by 2 kcal M⁻¹.

Keywords :

• Oxorhenium(V) complex
• Schiff-base ligand
• Electrochemistry
• DFT calculation

Acknowledgment

Financial support from the Department of Science and Technology, New Delhi, India (Project No. SR/FT/CS-75/2010G) is gratefully acknowledged.