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

Reaction of (Bu₄N)[ReOCl₄] with the tetradentate Schiff base ligand α,α′-[(1,1-dimethylethylene)dinitrilo]di-o- cresol (sal₂ibnH₂) yields cis-[Re^VOCl(sal ₂ibn)], which quickly forms trans-[μ-O(Re^VO(sal ₂ibn))₂] in solution. The dinuclear complex can also be isolated by the addition of base (Et₃N) to the reaction mixture. Conversely, the mononuclear complex can be trapped as cis-[Re ^VO(NCS)(sal₂ibn)] by addition of (Bu₄N)SCN to the reaction mixture. Reduction of cis-[Re^VO(NCS)sal₂ibn] with triphenylphosphine gives the rare trans-[Re^III(NCS)(PPh ₃)(sal₂ibn)] and unique μ-oxo Re(iv) dimer trans-[μ-O(Re^IV(NCS)(sal₂ibn))₂]. All of the complexes were characterized by ¹H and ¹³C NMR, FT-IR spectroscopy, electrospray ionization mass spectrometry (ESI-MS), cyclic voltammetry and single crystal X-ray diffraction.