Alcohol Oxidations by Schiff Base Manganese(III) Complexes

Abstract

Asymmetric Schiff base manganese(III) complexes involving salen ligands, N,N′-bis(salicylidene)2,3-diaminopyridine, N,N′-bis(3-methoxysalicylidene)2,3-diaminopyridine, N,N′bis(3,5-di-tert-butylsalicylidene)2,3-diaminopyridine and N,N′bis(3,5-di-chloro-salicylidene)2,3-diaminopyridine were prepared and their catalytic activity was investigated in the oxidation of some primary and secondary alcohols. During optimization of oxidation reactions, Mn-4, bearing electron withdrawing N,N′-Bis(3,5-di-chloro-salicylidene)2,3-diaminopyridine ligand, showed higher activity than other catalysts tested. The [a]

Manganese(iii) complexes stabilized with N-heterocyclic carbene ligands for alcohol oxidation catalysis

“…17 While the manganese(0) species accomplished full conversion in 2 h even at slightly lower temperature, complexes 1 and 2 feature catalytic rates that are six-fold higher (TOF max = 500 and 540 vs. 90 h −1 , respectively) and set a new benchmark for alcohol oxidation with NHC manganese catalysts. We note that related penta-coordinate Mn( iii )–salen and -salphen catalysts show considerably higher activity in alcohol oxidation (quantitative conversion in minutes), 9,51–54 even though using (NBu 4 )HSO 5 as a harsher terminal oxidant.…”

Manganese N,N,N-pincer complex-catalyzed epoxidation of unactivated aliphatic olefins

“…A similar behaviour is reported by the group of Todisco using imidazole for the activation of TBHP in a manganese-catalyzed oxidation reaction. 46 Then, the manganese( iii ) species undergoes homolysis generating the oxo-species L 1 Mn( iv )O(OTf) 2 and a tert -butyl radical (step B ). In the last step ( C ), the olefin 4 is oxidized to the epoxide 5 by the previously formed Mn( iv )O species.…”

A manganese-based catalyst system for general oxidation of unactivated olefins, alkanes, and alcohols

“…3 More specifically, the ultimate clean oxidant for liquid phase oxidation at ambient pressure is aqueous hydro-gen peroxide, which unfortunately can be easily decomposed, especially by non-noble metal salts, thus limiting its general applicability. To improve the selectivity and prevent decomposition reactions of peroxides, N-heterocyclic compounds have been used as (co-)ligands, [4][5][6][7][8] additives, 9 or bases 10 in metalcatalysed oxidation reactions. In fact, several multidentate ligands, e.g., pincer-type or tetradentate ligands, showed higher selectivities in oxidation reactions with oxidants like hydrogen peroxide or tert-butyl hydroperoxide (TBHP).…”