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 (N 2 O 2 ) Schiff base ligand sal 2 phen (N,N'-ophenylenebis(salicylaldimine)) was reacted with (n-Bu 4 N) [ReOCl 4 ] to yield trans-[ReOCl(sal 2 phen)] (1). On reaction with triphenylphosphine (PPh 3 ), a rearranged Re V product cis-[ReO(PPh 3 )(sal 2 phen*)]PF 6 (2), in which one of the imines was reduced to an amine during the reaction, and the reduced Re III products trans-[ReCl(PPh 3 )(sal 2 phen)] (4) and trans-[Re(PPh 3 ) 2 (sal 2 phen)] + (5) were isolated. Reaction of sal 2 phen with [ReCl 3 (PPh 3 ) 2 (CH 3 CN)] resulted in the isolation of [ReCl 2 (PPh 3 ) 2 (salphen)] (3). The compounds were characterized using standard spectroscopic methods, elemental analyses and single crystal X-ray crystallography.

Novel rhenium(iii, iv, and v) tetradentate N2O2 Schiff base mononuclear and dinuclear complexes

“…All dinuclear compounds exhibited the Re–O–Re stretch at 694 cm −1 . A signal at 980 cm −1 for the Re=O stretch, typical for multinuclear oxorhenium complexes, 10, 13, 19, 20, 25, 36 was observed for compound 2 and was absent in compound 5 . The thiocyanate containing complexes exhibited SCN stretches from 2050 – 2090 cm −1 , consistent with literature values.…”

“…5, 8, 9 Various rhenium Schiff base complexes have also been explored for potential applications to diagnostic and therapeutic nuclear medicine. 10–25 …”

“…10, 12–17, 19–22, 25, 28, 29 Mononuclear complexes ([ReOXL]) are generally isolated under dry, inert conditions using excess ligand as the proton scavenger. 10, 15, 19 Dinuclear (μ-O[ReOL] 2 ) and trinuclear ((μ-O) 2 O 2 [ReL] 3 ) species are a result of reactions performed open to the atmosphere or in the presence of basic proton scavengers, and have also been isolated as conversion products from mononuclear species that have been left in solutions exposed to water and/or base.…”

“…We previously reported on using a rigid Schiff base ligand (sal 2 phen) to generate the Re analog of the “Q-compounds”. 25 Now we report on using a sterically more hindered Schiff base to investigate the factors that might lead to trans -[Re(PR 3 ) 2 (Schiff base)] + . The reaction of (Bu 4 N)[ReOCl 4 ] with a salicylaldehyde based N 2 O 2 Schiff base ligand derived from 1,2-diamino-2-methylpropane (α,α’-[(1,1-dimethylethylene)dinitrilo]di- o -cresol, sal 2 ibnH 2 ) under various conditions led to several products (Scheme 1).…”

Benzoylamido-substituted thiazoles and thiazolidines and their rhenium complexes

“…The reduction of Re(V) to Re(III) by the addition of phosphines after the complexation of a chelating ligand to a Re(V) complex, however, is not unprecedented and has been described as an approach to maintain a distinct coordination sphere around the metal ion [7,19,20]. Figure 3 shows the molecular structure of one of the species.…”