MONOMETALLIC, HOMOROBIMETALLIC AND HETEROBIMETALLIC COMPLEXES BASED ON REDOX ACTIVE TRIS(3,5-DIMETHYLPYRAZOLYL)BORATO-MOLYBDENUM AND BORATO-TUNGSTEN NITROSYLS .1. META-SUBSTITUENT EFFECTS ON THE REDUCTION POTENTIALS OF MONOMETALLIC ARYLAMIDE COMPLEXES

The complexes [Mo(NO)LCl(NHC6H4-3-Z)] (L = HB(3,5-Me2C3N2H)3; Z = F, Cl, Br, Me, OMe, CF3, NO2), [W(NO)L(NHC6H4-3-Z)] (Z = F, Cl, Br, Me, OMe, COME, CF3, NO2) and [W(NO)L(NHC6H4-3-CF3)2] have been synthesized and characterized by spectroscopic methods. All of the monoarylamide complexes undergo one-electron reduction processes at potentials which vary according to the nature of Z. A linear correlation was found between the reduction potentials within each of the two series and the Hammett meta substituent parameters, σm, for Z. The respective reaction constants, ρ{variant}m, and intercepts, Ef0, are for [Mo(NO)LCl(NHC6H4-3-Z)], ρ{variant}m = 5.50 (0.39), Ef0 = -0.848 (0.009) V and for [W(NO)L(NHC6H4-3-Z)], ρ{variant}m = 4.75 (0.50), Ef0 1.291 (0.011) V. © 1990.