Diverse copper(II) complexes with simple nitrogen ligands: Structural characterization and applications in aerobic alcohol oxidations in water

New copper(II) species from the copper/2,2′-bypyridine and copper/4-dimethylaminopyridine catalyzed aerobic alcohol oxidations

“…In continuation with our previous work on the identification of new copper species involved in the copper-catalyzed aerobic alcohol oxidation reactions [11][12][13][14][15] Yellow-brown crystals that were previously characterized were first observed within two days, which, however, disappeared upon elongated exposure to the air without isolation [11].…”

“…Previously, monovalent Cu I salts were found to be more effective copper source for most of ligands studied, however, Cu II also showed comparable catalytic activity in many cases [6,7,[10][11][12][13][14][15]. Here, we conducted several catalytic experiments in order to disclose the reactivity difference between the Cu II /BPY/TEMPO and Cu II /DMAP/TEMPO catalyst systems, while using CuCl 2 as the copper source.…”

“…The continuing work revealed that a dinuclear Cu II complex displayed higher reactive activity than some analogues derived from simple monodentate nitrogen ligands structurally related to DMAP [12,13]. In addition, we also serendipitously isolated and characterized two novel mixed-valent Cu I Cu II assemblies (dimer or polymeric chain) based upon the chelating 2,2':6',2''-terpyridine ligands, in search of similar TEMPO-mediated aerobic oxidations of alcohols [14,15].…”

“…Recently, we were interested to investigate the influence of various organic ligands in the catalytic reactivity of Cu I -or Cu II -catalyzed aerobic alcohol oxidations, with a focus on the structural elucidation of possible Cu I or Cu II complexes formed during the catalytic reactions [10][11][12][13][14][15]. We have observed that tetranuclear copper clusters derived from N,O-Schiff base ligands catalyzed aerobic oxidations of benzylic alcohols under aqueous basic conditions, featuring higher activity than its dinuclear analogue [10].…”

“…While BPY was proved to be very efficient and tolerated a great scope of substrates [7], DMAP is unique for the aerobic oxidation of activated alcohols in pure water without the use of an extra base [12,13]. Herein, we focused on the comparison of the catalytic activity of these two simple nitrogen ligands (BPY and DMAP) for the Cu(II)-promoted aerobic oxidation of benzylic alcohol, as well as the attempted isolation and characterization of possible copper species involved in the catalytic process.…”