Synthesis, structure and applications of [cis-dioxomolybdenum(VI)-(ONO)] type complexes

Abstract

Oxo-molybdenum chemistry is of great interest since such units are found in the active sites of a majority of molybdo-enzymes. In order to mimic the biological systems, a number of oxo-molybdenum complexes have been synthesised and studied. This review describes synthesis, structure and applications of oxomolybdenum complexes particularly cis-MoO 2 (L)(D) where L stands for a dianionic tridentate ONO ligand and D for a donor solvent molecule/monodentate ligand. The ligand moieties are derived from Schiff base, hydrazide Schiff base and other related tridentate ligands L(H) 2 . The coordination geometry around the Mo center in these complexes can be best described as a distorted octahedron in which the ONO-tridentate ligand occupies meridional position with two anionic oxygen donors mutually trans and are cis to the oxygen centers of the cis-dioxo group. Mostly the applications of cis-MoO 2 -(ONO) type complexes seen in literature are oxo transfer reactions like epoxidation, sulfoxidation and phosphine oxidation reactions.

Synthesis and antioxidant activities of Schiff bases and their complexes: a review

“…The dioxygen coordination can occur via different modes, the preferred mode in each particular case depending on the ligand, and the species present in solution if the complexes are studied in solution . For example, Co.(salen) and salophen (https://en.wikipedia.org/wiki/Chemical_formula C 15 H 13 NO 4 ) complexes can form monomeric (superoxo) or dimeric (μ‐peroxo) adducts with dioxygen in neutral solution or in solid form.…”

“…Formation of p ‐quinones with this system depends on the coordination of the axial ligand to the metal as influenced by its p K a and its size. The yield of p ‐quinones from guaiacyl models was markedly improved by the addition of a sterically hindered aliphatic nitrogen base that does not coordinate to the catalyst …”

“…These studies revealed that aliphatic aldehydes and cyclic β‐ketoesters also act as good ligands to cobalt(II) Schiff base complex 1 ( 2 ) in promoting the formation of monomeric cobalt(III)–dioxygen species. Theses carbonyl compounds not only help in the formation of cobalt(II)–dioxygen species but also act as the reducing agent during oxygen atom transfer to organic substrates …”

(6Z)-4-Bromo-6-{[(2-hydroxyethyl)amino]methylidene}cyclohexa-2,4-dien-1-one

“…For the synthesis of a similar structure, see: Chakravarthy & Chand (2011). For reference bond-length data, see: Allen et al (1987).…”

“…The amino alcohol functionality is present in many classes of compounds having chemotherapeutic activity (Erdemir, 2012;Rubinstein & Svendsen, 1994;Thomas et al, 1990). In addition, phenolic compounds containing the aminoalcohol grouping in ortho positions act as excellent bidentate ligands for the formation of several metal complexes (Chakravarthy & Chand, 2011).…”