Synthesis, chemical and electrochemical studies of complexes of a tridentate ONS chelating ligand built around the elusive [MoVIOS]2+ core

Abstract

Synthesis and characterization of four Mo(VI) complexes of a diprotic tridentate ONS chelating ligand (H2L) containing the rather elusive [MoVIOS]2+ core is reported. These [MoVIOSL] complexes are obtained from their corresponding [MoVIO2L] precursors using a combination of PPh3 and PPh3S. This process of oxo-abstraction and sulfido-inclusion affected by PPh3–PPh3S is reported for the first time and may be considered as a general method of converting [MoVIO2L] complexes to the corresponding [MoVIOSL] complexes. Direct structural characterization of these complexes could not be done due to the ease of solvolysis of these oxosulfidomolybdenum(VI) complexes to the corresponding dioxomolybdenum(VI) analogues. However, the structure of these [MoVIOSL] complexes could be reasonably surmised from the corresponding structurally characterized [MoVIO2L] complexes. Points of attachment of the potentially pentadentate but functionally tridentate ONS chelating ligands to [MoVIOS]2+ are located mainly through analysis of IR and UV-Vis spectral data and comparison with corresponding [MoVIO2L] complexes of known structure. Conditions under which solvolysis of [MoVIOS]2+ to the [MoVIO2]2+ core is significantly retarded have been identified and make us hopeful of obtaining single crystals of [MoVIOSL].