Selective and Effective Stabilization of MoVIO Bonds by NH···S Hydrogen Bonds via Trans Influence

A monooxomolybdenum(IV) complex containing two intramolecular NH···S hydrogen bonds, (NEt4)2[MoIVO(1,2-S2-3-t-BuNHCOC6H3)2], was synthesized. The trans isomer was crystallized as the major product, and the molecular structure was determined by X-ray analysis. The trans isomer was isomerized by heating in solution to give a 1:1 mixture of trans and cis isomers. Oxidation of these isomers by Me3NO afforded (NEt4)2[MoVIO2(1,2-S2-3-t-BuNHCOC6H3)2]. 1H NMR analysis revealed that the dioxomolybdenum(VI) complex existed as a single isomer where both oxo ligands were trans to each of the two hydrogen-bonded thiolate ligands. The MoVIO bond was effectively stabilized by the NH···S hydrogen bond via trans influence, which was determined using resonance Raman spectroscopy. These results were supported by preliminary density functional theory calculations.