Copper(ii) induced oxidative modification and complexation of a schiff base ligand: synthesis, crystal structure, catalytic oxidation of aromatic hydrocarbons and DFT calculation

Abstract

A mononuclear square planar complex [CuII(L2f)], formed from a Schiff base H2La and Cu2+ with the concomitant oxidation of two –CH2OH groups to aldehyde, displayed catalytic oxidation of aromatic hydrocarbons.

New copper(II) salicylaldimine derivatives for mild oxidation of cyclohexane

“…The band at 630 nm was attributed to a metal to ligand charge transfer (MLCT) between the Cu(II) centre and the non-bonding orbital of the azomethine (C=N) moiety. Similar observations are reported in the literature for salicyaldiminato-Cu(II) complexes, 9,13 suggesting formation of a distorted square planar geometry for complexes 1 and 2. Formation of 1 and 2 was further confirmed by high resolution ESI-MS + .…”

“…The molecular structures of complexes 1 and 2 are depicted in Figure 2. The C-N and C-O bond distances for 1 (1.893 Å) and 2 (1.917(2) Å) were within reported limits for similar compounds 9,13 while the dihedral angles defined by O(1)-Cu 1 around the chelating environment, with the tert-butyl susbstituents in 6-positions preventing coplanarity, is a likely reason for the observed deviation. Complex 1 displays a static/flip disorder of about 180 o in the thiophenyl moiety with a partial occupancy of the carbon site by the sulfur atom.…”

“…5 The literature reveals a limited number of copper(II) complexes with sterically demanding tert-butyl substituents on the salicylaldimine ligands. [6][7][8] Also, only a limited number of mono-, [9][10][11][12][13] di-, [14][15][16] and multinuclear [17][18][19][20] copper(II) complexes have been reported to catalytically functionalize C-H bond of alkanes under mild reaction conditions. Some salicylaldiminato-copper(II) complexes have been shown to catalyse a range of chemical reactions such as selective aerobic oxidation of primary alcohols to corresponding aldehydes.…”

“…It was shown that the presence of a pendant pyrazolyl arm stabilizes the copper(II)-hydroperoxo intermediate [LCu−OOH] − via formation of hydrogen bonding. 9,13 Such hydrogen bond interaction has been shown to be vital for the stabilization of the rather unstable intermediate [LCu(II)-OOH]. 34a We wished to expand the scope of sterically demanding tert-butyl salicylaldiminato-copper complexes by preparing the bis-…”

Theoretical and experimental studies on three new coordination complexes of Co(II), Ni(II), and Cu(II) with 2,4-dichloro-6-{(E)-[(5-chloro-2 sulfanylphenyl)imino]methyl}phenol Schiff base ligand

“…These compounds are successfully utilized as sensor [18], fluorescence materials [19,20], non-linear optics [21,22], nano-precursor [23,24], magnetic materials [25], dye sensitized solar cells [26], OLEDs [27], and have a wide range of catalytic applications such as in polymerization, olefin oxidation, epoxidation, Michael addition reaction, Heck reaction etc. [28][29][30][31].…”