Monooxo molybdenum(VI)complexes with catecholate and 2,2'-thiobis(phenolate)ligands:preparation and electrochemical and spectroscopic properties

摘要

Preparation,spectroscopic characterization and electrochemical behavior are reported for the six-coordinate monooxo Mo(VI) complexes,MoOL(cat),where L~(2-)=2,2'-thiobis(4-methyl-6-tert-butylphenolate) or 2,2'-thiobis(4,6-di-tert-butylphenolate) and cat~(2-)=catecholate (Cat~(2-)),4-methylcatecholate (Mecat~(2-)),4-nitrocatecholate (NO_2cat~(2-)),or 3,5-di-tert-butylcatecholate (DTBcat~(2-)).The compounds are prepared by reaction of catechol with Mo_2O_3L_2,the #mu#-oxo Mo(V)dimer produced by reaction of MoO_2(acac)_2 with H_2L.MoOL(cat)complexes exhibit a Mo=O stretching vibration (v_(Mo=O))at 949-961 cm~(-1) and a reversible Mo(VI/V)reduction at -0.3 to -0.6 V versus Fc~(+/0).These features are characteristic of a mononuclear MoO~(4+) center.The kinetics of the metal-centered electrode reaction is sensitive to the catechol substituent.Under identical experimental conditions,the apparent electron-transfer rate indicated by the voltammetric peak potential separation (#DELTA#E_p) increases in the following sequence:DTBcat~(2-)