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

Abstract

Synthesis and characterization of four Mo(VI) complexes of a diprotic tridentate ONS chelating ligand (H₂L) containing the rather elusive [Mo^VIOS]²⁺ core is reported. These [Mo^VIOSL] complexes are obtained from their corresponding [Mo^VIO₂L] 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 [Mo^VIO₂L] complexes to the corresponding [Mo^VIOSL] 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 [Mo^VIOSL] complexes could be reasonably surmised from the corresponding structurally characterized [Mo^VIO₂L] complexes. Points of attachment of the potentially pentadentate but functionally tridentate ONS chelating ligands to [Mo^VIOS]²⁺ are located mainly through analysis of IR and UV-Vis spectral data and comparison with corresponding [Mo^VIO₂L] complexes of known structure. Conditions under which solvolysis of [Mo^VIOS]²⁺ to the [Mo^VIO₂]²⁺ core is significantly retarded have been identified and make us hopeful of obtaining single crystals of [Mo^VIOSL].

Keywords:

• Oxosulfido Mo(VI) complexes
• Functionally tridentate ONS ligands
• PPh₃–PPh₃S combination
• Facile SAT in solution
• Cyanolysis of the Mo=S bond

Acknowledgements

M. S. is grateful to the Council of Scientific and Industrial Research (New Delhi) for the award of senior research fellowship.