Homoleptic Molybdenum Cluster Sulfides Functionalized with Noninnocent Diimine Ligands: Synthesis, Structure, and Redox Behavior

Thiourea (tu) has been coordinated to the Mo3S44+ cluster unit to afford the new cluster compound [Mo3S4(tu)8(H2O)]Cl4·4H2O (1). The high substitutional lability of the thiourea ligands can be exploited to achieve smooth ligand substitution in the Mo3S4 cluster. The reactions of 1 with 1,10-phenanthroline (phen) and 2,2′-bipyridine (bpy) have resulted in new trisubstituted diimino complexes [Mo3S4Cl3L3]+ [L = phen (2), bpy (3)]. The crystal structure of [Mo3S4Cl3(phen)3]Cl·4H2O was determined by X-ray analysis. A solid-state cyclic voltammetry study of 2 shows a ligand-centered reversible two-electron reduction. DFT calculations for [Mo3S4Cl3(phen)3]+ and the 2e-reduced species [Mo3S4Cl3(phen)3]– support our interpretation of the reduction process. Compound 3 undergoes a reversible two-electron reduction, which is more metal-centered on the basis of DFT calculations