Perchlorate reduction catalyzed by dioxidomolybdenum(VI) complexes: Effect of ligand substituents

Mimicking the molybdoenzyme (per)chlorate reductase allows for the development of homogeneous catalysts capable of reducing perchlorate. Here, we report several novel dioxidomolybdenum(VI) complexes, [MoO2(SN)(2)] (SN = bidentate ligand) employing 5-nitro-6-methylpyridine-2-thiolate, 4-(trifluoromethyl) pyrimidine-2-thiolate, 3-chloropyridine-2-thiolate, 3-methylpyridine-2-thiolate as well as the literature-known [MoO2(PyS)(2)], (PyS = pyridine-2-thiolate) as homogeneous catalysts for perchlorate reduction. These complexes were designed and chosen to evaluate the electronic effect of the ligands on the catalytic activity. Using PPh3 as a sacrificial oxygen acceptor, we followed the reduction of ClO4 indirectly by the determination of the conversion of PPh3 to OPPh3 by GC-MS, under different catalytic conditions. Electron-withdrawing substituents were found to reduce the kinetic barrier for the initial oxygen atom transfer reaction from [Mo(VI)O2L2] to PPh3 supported by kinetic investigations using UV-Vis spectroscopy. However, their presence also decreases the stability of the complexes under the explored conditions. (c) 2022 Published by Elsevier Inc.

Automated summary

This study reports several novel dioxidomolybdenum(VI) complexes as homogeneous catalysts for perchlorate reduction, evaluating the effect of ligands on catalytic activity.