Synthesis and redox properties of cis-[ReCl(NCR)(Ph2PCH2CH2PPh2)2](R = alkyl or aryl) complexes with a cis-phosphine rhenium(I) centre

Abstract

Treatment of a solution of trans-[ReCl(N₂)(dppe)₂](dppe = Ph₂PCH₂CH₂PPh₂) in toluene with the appropriate organonitrile in sunlight afforded cis-[ReCl(NCR)(dppe)₂]1(R = C₆H₄NEt₂-4, C₆H₄OMe-4, C₆H₄Me-4, Ph, C₆H₄F-4, C₆H₄Cl-4, C₆H₄NO₂-4, CH₂C₆H₄Cl-4, Et, Prⁱ or Bu^t) the ³¹P-{¹H} NMR spectra of which have been analysed as ABCD spin systems. Cyclic voltammograms of the complexes, in aprotic medium at a Pt electrode, show a single-electron reversible oxidation at half-wave anodic potentials (¹E_½^ox) in the range –0.20 to –0.02 V vs. saturated calomel electrode (at –20 °C) which is followed by a second anodic process at a higher potential. For the aromatic nitriles, direct or inverse linear correlations are observed between ¹E_½^ox and the Hammett constant, σ_p′, of the phenyl substituent or the ν(NC) frequency, respectively.