SYNTHESIS AND REDOX PROPERTIES OF CIS-[RECL(NCR)(PH2PCH2CH2PPH2)2] (R=ALKYL OR ARYL) COMPLEXES WITH A CIS-PHOSPHINE RHENIUM(I) CENTER

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, Pr(i) or Bu(t)) the P-31-{H-1} 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 ((I)E1/2ox) in the range -0.20 to -0.02 V vs. saturated calomel electrode (at -20-degrees-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 (I)E1/2ox and the Hammett constant, sigma(p), of the phenyl substituent or the v(NC) frequency, respectively.