Novel vanadium(iii) complexes with rigid phenylpolycarboxylate ligands: synthesis, structures and application in C–H bond activation

Abstract

Two novel vanadium(III) complexes: V(dipic)(Hbdc)(H2O)2 (1) and [V2(dipic)2(H2btec)(H2O)4]·2H2O (2) (H2dipic = 2,6-pyridinedicarboxylic acid, H2bdc = 1,3-benzene-dicarboxylic acid, H4btec = 1,2,4,5-benzenetetracarboxylic acid) are synthesized by the reaction of V2(SO4)3, 2,6-pyridinedicarboxylic acid and 1,3-benzene-dicarboxylic acid (for 1) or 1,2,4,5-benzenetetracarboxylic acid (for 2) under hydrothermal condition at 120 °C for 3 days. They were characterized by elemental analysis, IR, UV-Vis, single crystal X-ray diffraction analysis and thermogravimetric analyses (TG). Structural analyses show that the vanadium atoms in the complexes 1 and 2 are both in a pentagonal-bipyramidal coordination environment with the NO6 donor set, and there is intermolecular hydrogen bonding in each complex. Research results found that the complexes exhibited bromination catalytic activity in the single-pot reaction of the conversion of phenol red to bromophenol blue in the mixed solution of H2O-DMF at the constant temperature of 30 ± 0.5 °C with pH = 5.8, and catalytic C-H bond cleavage activity for the peroxidative oxidation (with hydrogen peroxide) of cyclohexane to cyclohexanol and cyclohexanone (the maximum total turnover number is 395) under the mild conditions.

Synthesis, structures, and catalytic studies of new copper(II) complexes with arene-linked pyrazolyl methane ligands

“…We found that a copper complex could be used in catalyzing oxidative bromination, the catalytic activity of which is similar to that of the bromoperoxidase [30]. For exploring new stable biomimetic catalysts and effect of different kinds of ligands on the catalytic activity, we have chosen two arene-linked pyrazolyl methanes as ligands, 1,4-bis((1H-pyrazol-1-yl)methyl)benzene (L1) and 1,4-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)benzene (L2), to synthesize two new copper complexes, [Cu 2 …”

Preparation, characterization, crystal structures and catalytic oxidation activities of two transition metal complexes of an N-heterocyclic pincer ligand

“…Hence Cy cannot be effectively oxidized by H 2 O 2 without the participation of an acid additive, with conversions of only 6-8 % (entries 1 and 2). Upon the addition of HNO 3 to the system, similar complexes often show high catalytic activities [28][29][30]. However, complexes 1 and 2 were still inert for Cy oxidation with HNO 3 as additive (entry 3), although the conversion was reached to 75/88 %.…”

Investigation into experimental conditions and factors for cyclohexane oxidation with VO(acac)2

“…To our best knowledge, the Cy oxidation promoted by some iron-chromium, vanadium and copper complexes is more efficiently in acidic media [34][35][36][37] , such as HNO 3 [6,8,9] , CH 3 COOH [34] , CCl 3 COOH [34] , HCl [34] , H 2 SO 4 [34] , oxalic acid [14,38] , pyrazine-2,3-dicarboxylic acid [38] and pyrazine-2-carboxylic acid [39] .…”

“…Pokutsa et al [14] advised that oxalic acid and glyoxal can noticeably increase the catalytic activity of VO(acac) 2 in Cy oxidation. However, the investigation on the effective additives for the VO(acac) 2 [9] . Herein, we found that the VO(acac) 2 -catalyzed process can be strongly improved by o(m,p)-phthalic acid.…”

“…To achieve a good activity, efforts have been devoted to searching for more active catalysts under mild conditions. Heterogeneous catalysts, such as zeolites [3] , metals and metal oxides [4] , and homogeneous catalysts, such as cobalt [5,6] , copper [7] , molybdenum [8] , vanadium [2,9] and iron [10] complexes, have been reported as potential catalysts for Cy oxidation.…”