Monometallic, homo- and hetero-bimetallic complexes based on redox-active tris(3,5-dimethylpyrazolyl)borato molybdenum and tungsten nitrosyls. Part 8. Complexes exhibiting weak or intermediate interaction between two redox centres

Abstract

The complexes [ML(NO)X(NHQNH2)][L = tris(3,5-dimethylpyrazolyl)borate; M = Mo, X = I, Q =(C6H4)2Y where Y = O, SO2, CH2, or CH2CH2; M = W, X = Cl, Q =(C6H4)2O], [MoL(NO)I(NHCH2CH2C6H4NH2)], [ML(NO)X(OQOH)][M = Mo, X = I, Q =(C6H4)2Y where Y = nothing or S; X = Cl, Q =(C6H4)2S], and [ML(NO)X(OCH2C6H4CH2OH)](M = Mo, X = I; M = W, X = Cl) have been prepared. The bimetallic complexes [{ML(NO)X}2(NHQNH)][M = Mo, X = I, Q =(C6H4)2Y where Y = O, SO2, CH2, or CH2CH2; M = W, X = Cl, Q =(C6H4)2O], [{MoL(NO)I}2(NHCH2CH2C6H4NH)], [{MoL(NO)X}2(OQO)][X = I, Q =(C6H4)2 Y where Y = nothing or S; X = Cl, Q =(C6H4)2 Y where Y = nothing, S, SO2, CO, or COC6H4C6H4CO], and [{ML(NO)X}2(OCH2C6H4CH2O)](M = Mo, X = I; M = W, X = Cl) were obtained either from the monometallics by reaction with [ML(NO)X2] or by direct reaction of the latter with the appropriate arylamine or phenol. The heterobimetallic [MoL(NO)I(NHC6H4OC6H4NH)WL(NO)Cl] was also prepared and all compounds were characterised spectroscopically. The monometallic species underwent a single, usually reversible, one-electron reduction determined by cyclic voltammetry (in CH3CN using a Pt electrode). Values of E½ were dependent on M, X, and the nature of the heteroatom ligand. The bimetallic species underwent two one-electron reductions, investigated by differential pulse polarography. The separation between the redox potentials (ΔE½) varied from 45 mV (negligible interaction between redox centres) to 138 mV (weak interaction), depending on the nature of the bridging ligand.