78790-97-3Relevant articles and documents
Ligand control of the redox properties of dioxomolybdenum(VI) coordination complexes
Topich, Joseph
, p. 3704 - 3707 (1981)
Several new cis-dioxomolybdenum(VI) coordination complexes have been synthesized incorporating dibasic tridentate Schiff-base ligands derived from 5-substituted salicylaldehydes and o-aminophenol, 2-aminoethanol, or anthranilic acid. The synthesis and characterization of these complexes are described. Cyclic voltammetry was used to obtain cathodic reduction potentials (Epc) for the irreversible reduction of the Mo(VI) complexes. The substituent on the salicylaldehyde portion of the ligand causes rather substantial differences in the Epc's that are observed for the Mo(VI) complexes. Electron-withdrawing substituents cause an anodic shift in Epc while the opposite effect is observed for electron-donating ligand substituents. Within a series of Mo complexes, a potential range of ～200 mV is spanned, and a linear relationship is observed between Epc and the Hammett σp parameter for the ligand substituent. In addition to substituent effects within each series, there are structural effects between series that are important. Ligand delocalization and the substitution of a carboxylic acid group for the phenolic oxygen donor atom facilitate Mo complex reducibility. The trends in Epc are also manifested in shifts observed in the low-energy ligand-to-metal charge-transfer transitions, and these are also discussed.
