Kinetic and spectroscopic observations on the azidyl, image, radical oxidation of fac-(Lspectator)ReI(CO)3(Lacceptor) to fac-(Lspectator)ReII(CO)3(Lacceptor), Lspectator = 4,4′-bpy; Lacceptor = dipyridyl[3,2-a:2′3′-c]phenazine or Lspectator = Cl−; Laccept

The oxidation of two triscarbonyl fac-(Lspectator)ReI(CO)3(Lacceptor)z complexes (Lspectator = 4,4′-bpy; Lacceptor = dipyridyl[3,2-a:2′3′-c]phenazine (dppz) and z = + or Lspectator = Cl−; Lacceptor = bathocuproinedisulfonate (bcds2−) and z = 2-) by azidyl radicals, View the MathML sourceN3, was investigated by pulse radiolysis. Reaction rate constants were determined for the electron transfer reactions between the Re(II) products and reductants, View the MathML sourceRu(bipy)33+ and Ni(Me6-[14]dieneN4)2+, and used for the calculation of the self-exchange rate constant of the Re(II)/Re(I) couples. The self-exchange rate constants, k ∼ 107 M−1 s−1, were one order of magnitude larger than the constant, k ∼ 106 M−1 s−1, communicated in the literature for the [Re(DMPE)3]+/2+ (DMPE = 1,2-bis(dimethylphosphine)ethane). The larger rate constants of the triscarbonyl complexes are in agreement with the smaller inner sphere reorganization energy of the complexes relative to [Re(DMPE)3]+/2+. Moreover, the study demonstrated that the redox potential of the azidyl radicals is View the MathML sourceEN3/N3-0=1.70VversusNHE, a value larger than one communicated earlier, and that the self-exchange rate constant of the View the MathML sourceN3/N3- couple is View the MathML sourcekN3/N3-=2.7×106M-1s-1. The small value of the View the MathML sourceN3/N3- self-exchange rate constant has been related to the large solvent reorganization energy of the reaction.