Kinetic and spectroscopic observations on the azidyl, N3•, radical oxidation of fac-(Lspectator)ReI(CO)3(Lacceptor) to of fac-(Lspectator)ReII(CO)3(Lacceptor), Lspectator = 4,4´-bpy; Lacceptor = dipyridil[3,2-a:2’3’-c]phenazine or Lspectator = Cl-; Laccep

G.T. RUIZ; M.P. JULIARENA; E.WOLCAN; G. FERRAUDI.

INORGANICA CHIMICA ACTA

Elsevier B.V

Año: 2007 vol. 360 p. 3681 - 3687

0020-1693

Abstract 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, N3• , was investigated by pulse radiolysis. Reaction rate constants were determined for the electron transfer reactions between the Re(II) products and reductants, Ru(bipy)32+ 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 E0N3•/N3– = 1.70 V vs NHE, a value larger than one communicated earlier, and that the self-exchange rate constant of the N3•/N3– couple is k N3•/N3– = 2.7 x 106 M-1 s-1. The small value of the N3•/N3– self-exchange rate constant has been related to the large solvent reorganization energy of the reaction.