Re(v) and Re(iii) complexes with sal2phen and triphenylphosphine: rearrangement, oxidation and reduction

Abstract

Reactions of Re^V, tetradentate Schiff base complexes with tertiary phosphines have previously yielded both rearranged Re^V and reduced Re^III complexes. To further understand this chemistry, the rigid diiminediphenol (N₂O₂) Schiff base ligand sal₂phen (N,N′-o-phenylenebis(salicylaldimine)) was reacted with (n-Bu₄N)[ReOCl₄] to yield trans-[ReOCl(sal₂phen)] (1). On reaction with triphenylphosphine (PPh₃), a rearranged Re^V product cis-[ReO(PPh₃)(sal₂phen*)]PF₆ (2), in which one of the imines was reduced to an amine during the reaction, and the reduced Re^III products trans-[ReCl(PPh₃)(sal₂phen)] (4) and trans-[Re(PPh₃)₂(sal₂phen)]⁺ (5) were isolated. Reaction of sal₂phen with [ReCl₃(PPh₃)₂(CH₃CN)] resulted in the isolation of [ReCl₂(PPh₃)₂(salphen)] (3). The compounds were characterized using standard spectroscopic methods, elemental analyses and single crystal X-ray crystallography.