Synthesis, structure and dioxygen reactivity of Ni(II) complexes with mono-, bis-, tetra- and hexa-oxime ligands
摘要:
Four nickel complexes with beta-(oximinoalkyl)amine ligands Ox(n)H(n) containing one (Ox(1)H(1)), two (Ox(2)H(2)), four (Ox(4)H(4)) and six (Ox(6)H(6)) oxime groups were synthesized and characterized by elemental analysis, FTIR, HRMS and single crystal X-ray diffraction. beta-Oximinoalkylamines Ox(n)H(n) 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) beta-oximinoalkylamine complexes containing two ligands per one nickel ion (Ni(Ox(1)H(1))(2)Cl-2 and Ni(Ox(2)H(2))(2)Cl-2) were identified. Dioxygen reactivity of the obtained complexes in aerobic oxidation of triphenylphosphine was studied. Bis-oxime complex Ni(Ox(2)H(2))(2)Cl-2 was found to be the most active promoter of triphenylphosphine oxidation among the synthesized nickel complexes. (C) 2014 Elsevier Ltd. All rights reserved.