Monometallic, homo- and heterobimetallic complexes based on redox active tris(3,5-dimethylpyrazolyl)borato-molybdenum and -tungsten nitrosyls—I. Meta substituent effects on the reduction potentials of monometallic arylamide complexes

Abstract

The complexes [Mo(NO)LCl(NHC 6H 4-3-Z)] (L = HB(3,5-Me 2C 3N 2H) 3; Z = F, Cl, Br, Me, OMe, CF 3, NO 2), [W(NO)L(NHC 6H 4-3-Z)] (Z = F, Cl, Br, Me, OMe, COME, CF 3, NO 2) and [W(NO)L(NHC 6H 4-3-CF 3) 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, σ m , for Z. The respective reaction constants, ϱ m , and intercepts, E f 0, are for [Mo(NO)LCl(NHC 6H 4-3-Z)], ϱ m = 5.50 (0.39), E f 0 = −0.848 (0.009) V and for [W(NO)L(NHC 6H 4-3-Z)], ϱ m = 4.75 (0.50), E f 0 1.291 (0.011) V.