Synthesis, structure, spectroscopic characterization and catalytic activity of chiral dioxidomolybdenum(VI) Schiff base complexes derived from R(−)-2-amino-1-propanol

Synthesis, spectroscopic characterization and catalytic activity of cis‐dioxidomolybdenum (VI) complexes with chiral tetradentate Schiff bases

“…As we have previously reported, [ 21,22 ] the oxidation of styrene with catalytic amounts of molybdenum (VI) Schiff base complexes using aqueous 30% H 2 O 2 or TBHP as the terminal oxidants generally can result in five oxidation products, i.e. styrene oxide, benzaldehyde, benzoic acid, phenylacetaldehyde and 1‐phenylethane‐1,2‐diol.…”

“…For example in the cases of MoO 2 L 2 , MoO 2 L 3 and MoO 2 L 7 , the decrease in the reaction temperature was accompanied by longer reaction time but also a slight increase in enantioselectivity and without additional sulfone production (entries 3, 5, 10, 16, 18 and 23). In comparison with the other chiral but tridentate cis ‐dioxidomolybdenum (VI) Schiff base complexes, derived from amino alcohols, the conversions to thioanisole were similar, [ 21,22,33 ] but much higher amounts of catalysts (5 mol%) were needed to achieve them. Nevertheless, it seems that pathway for the formation of sulfoxide is very similar.…”

“…We reported earlier that cis ‐dioxidomolybdenum (VI), but also oxidovanadium(V) and cis ‐dioxidovanadium(V) complexes with unsymmetrical tridentate Schiff base ligands, products of monocondensation reaction of salicylaldehyde and its derivatives with amino alcohols and diamines, have been proven to possess a rigid and nearly planar backbone composed of three donor centers established by the Schiff base linkage, which prefer only a meridional coordination mode. [ 22,30 ] Moreover, such complexes with similar high‐density ligands, i.e. pentadentate Schiff bases, also revealed only meridional arrangement of coordination sites.…”

“…We have an ongoing interest in the chemistry of dioxidomolybdenum (VI) complexes using different ONO tridentate donor ligands. [ 21,22 ] In this paper we describe 10 new cis ‐dioxidomolybdenum (VI) complexes with tetradentate ONOO Schiff base ligands, products of a single condensation of 1S , 2S ‐(+)‐2‐amino‐1‐(4‐nitrophenyl)‐1,3‐propanediol with salicylaldehyde and its derivatives, presented in Figure 1. Very detailed investigation of their spectroscopic properties using IR, UV–vis, circular dichroism and one‐ and two‐dimensional NMR techniques has been also performed.…”

Remarkable binuclear Schiff‐based complex catalyze the epoxidation of alkenes: effects of substituent group

“…The peaks in the range of 230–245 nm could be attributed to the ligand absorption peaks . The absorption band at 270–400 nm was attributed to charge transfer from ligand to Mo . After adding TBHP, the absorption peak of 270–400 nm decreased sharply.…”