Synthesis, structure and dioxygen reactivity of Ni(II) complexes with mono-, bis-, tetra- and hexa-oxime ligands

Four nickel complexes with β-(oximinoalkyl)amine ligands OxnHn containing one (Ox1H1), two (Ox2H2), four (Ox4H4) and six (Ox6H6) oxime groups were synthesized and characterized by elemental analysis, FTIR, HRMS and single crystal X-ray diffraction. β-Oximinoalkylamines OxnHn act as polydentate ligands forming five-membered chelate rings, in which nickel is coordinated with both amine and oxime nitrogen atoms. In all structurally characterized complexes, OH-groups of oximes arms are involved in hydrogen bonding with counterions (Cl−), which are located in the inner or outer coordination sphere of the nickel atom. Two new structural types of pseudo-octahedral Ni(II) β-oximinoalkylamine complexes containing two ligands per one nickel ion (Ni(Ox1H1)2Cl2 and Ni(Ox2H2)2Cl2) were identified. Dioxygen reactivity of the obtained complexes in aerobic oxidation of triphenylphosphine was studied. Bis-oxime complex Ni(Ox2H2)2Cl2 was found to be the most active promoter of triphenylphosphine oxidation among the synthesized nickel complexes.

Four new Ni(II) complexes with β-oximinoalkylamines containing one (Ox1H1), two (Ox2H2), four (Ox4H4) and six (Ox6H6) oxime groups were synthesized and characterized. Oxidation of Ph3P with molecular oxygen in presence of these complexes was studied. Bis-oxime complex Ni(Ox2H2)2Cl2 was found to be the most active oxidation promoter among the obtained nickel complexes.Figure optionsDownload as PowerPoint slide