Synthesis and characterization of cis-Mo(CO)4(L–L′) and cis-Mo(CO)2(L–L′)2 complexes of N(1)-methyl-2-(arylazo)imidazoles (L–L′). Correlations of spectroscopic data with substituent effects

N(1)-Methyl-2-(p-X-phenylazo)imidazoles (L–L′; X=CH3O, CH3, H, Br, CF3, NO2) react with cis-(norbornadiene)Mo(CO)4 and Mo(CO)3(CH3CN)3 to provide the complexes cis-Mo(CO)4(L–L′) (X=CH3O, CH3, H, Br, CF3, NO2) and cis-Mo(CO)2(L–L′)2 (X=CH3, H, Br, CF3), respectively. The complexes were characterized by visible and infrared spectroscopy, by 1H-, 13C- and 95Mo-NMR spectroscopy, and by cyclic voltammetry. Correlations among the data and correlations of the data with the Hammett sigma parameter within each set of complexes were investigated and are generally very good. These data, as well as the inability to synthesize complexes of the type Mo(L–L′)3, indicate that 2-(arylazo)imidazoles are less effective ligands at stabilizing complexes of zerovalent metals than are 2-(arylazo)pyridines.