A new phenylimidorhenium(V) compound containing the 2-[(2-hydroxyethylimino)methyl]phenol Schiff-base ligand: experimental and theoretical aspects

<div><p>Reaction of equimolar <i>trans</i>-[Re(NPh)(PPh<sub>3</sub>)<sub>2</sub>Cl<sub>3</sub>] with H<sub>2</sub>L, a 1 : 1 Schiff-base condensate of salicylaldehyde and ethanolamine, in chloroform gives <i>trans</i>-[Re(NPh)(HL)(PPh<sub>3</sub>)Cl<sub>2</sub>] (<b>1a</b>) in good yield. <b>1a</b> has been characterized by C, H, and N microanalyses, FTIR and UV–vis spectra. The X-ray crystal structure of <b>1a</b> reveals that it is an octahedral <i>trans</i>-<i>Cl,Cl</i> phenylimidorhenium(V) complex. The rhenium center has an ‘N<sub>2</sub>OCl<sub>2</sub>P’ coordination sphere. <b>1a</b> crystallizes in the monoclinic space group P2<sub>1</sub>/c with <i>a</i> = 11.2391(5), <i>b</i> = 16.4848(7), <i>c</i> = 16.3761(8) Å, <i>V</i> = 3034.0(2) Å<sup>3</sup> and <i>Z</i> = 4. The electrochemical aspects of <b>1a</b> have been studied. Electrochemical studies of <b>1a</b> in dichloromethane show a quasi-reversible Re(V) to Re(VI) oxidation at 1.128 V <i>versus</i> Ag/AgCl. This redox potential reasonably matches the calculated redox potential, 1.186 V <i>versus</i> Ag/AgCl. Geometry optimization of the <i>trans</i>-<i>Cl,Cl</i><b>1a</b> vis-à-vis its <i>cis</i> analog, <i>cis</i>-<i>Cl,Cl</i><b>1b</b>, have been performed at the level of density functional theory (DFT). It is revealed that <b>1a</b> is more stable than <b>1b</b> by 21.6 kcal per mole of energy in the gas phase.</p></div>