Molybdenum complexes. 1. Acceptor behavior and related properties of MoVIO2(tridentate) systems

Article abstract of DOI:10.1021/ic50217a005

Molybdenum(VI) complexes of the type MoO₂(L), where L is a tridentate dianionic Schiff base ligand, are reported. Infrared data suggest oligomerization via a Mo=O→Mo bridge which is cleaved by a wide variety of donors (D): aldehyde, amide, amine, N-oxide, sulfoxide, phosphine oxide, water, alcohol, and phosphine-producing MoO₂(L)(D). The tendency of adduct formation by the molybdenyl systems increases in a particular way as L is changed. MoO₂(L)(D) usually shows two IR absorptions attributable to cis-MoO₂ stretches, and on the average, species with oxygen donors vibrate at higher frequencies than those with nitrogen donors. On the basis of ligand displacement reactions D binding increases in the order CH₃CHO < C₆H₅CHO < EtOH < p-anisaldehyde < dmf < pic < Me₂SO < im < py-N-O. On being heated, MoO₂(L)(D) is readily converted to MoO₂(L) in a single endothermic step. Thermal analysis data together with NMR data support the weak binding of the D ligands. The electron transfer characteristics of a number of the MoO₂(L)(dmf) species are studied with use of voltammetric techniques. In general two to three reduction waves are observed, all located at potentials more negative than -0.9 V vs. SCE. The chemistry and electrochemistry of a dinuclear molybdenum(V) species resulting from hydrazine reduction of one MoO₂(L) is also briefly described.