ELECTRON-PARAMAGNETIC RESONANCE STRUCTURAL STUDIES OF MOLYBDENUM(V)-OXO COMPLEXES

EPR and optical spectral data are reported for (NH4)2MoOCl5 and a series of its derivatives: M0OCl3L, where L = o-phenanthroline and a, a'-bipyridyl; MoOC1L2, where L = acetylacetone, 8-hydroxyquinoline, and 8-mercaptoquinoline; MoOCIL, where L = disalicylaldehyde o-phenylenediimine, N, N'-dimethyl-N, N'-bis(2-mercaptoethyl)ethylenediamine, and N, N'-bis(2-methyl-2-mercaptopropyl)ethylenediamine; Et4NMoOCl2L, where L = salicylaldehyde o-hydroxyanil. EPR measurements were made at both X (9.5 GHz) and Q (35 GHz) band frequencies. Several of the compounds have noncoincident g and nuclear hyperfine tensors which aid in assigning geometrical isomers in dimethylformamide solutions. The results are discussed in terms of the molecular and electronic structures of the above compounds and their relationship to the Mo center in xanthine oxidase. The spin-orbit coupling of chloride ligands does not appear to be the dominant mechanism contributing to the g shift. © 1979, American Chemical Society. All rights reserved.