Bis[(methanol){N-salicylidene-N′-(2-phenylimidazol-4-ylmethylidene)- 1,3-propanediaminato}nickel(II)] Bridged by Di-μ-phenoxo Moiety and the Deorotonated Imidazolate-Bridged Cyclic-Tetranuclear Complex

Article abstract of DOI:10.1246/bcsj.71.1831

Protonated and deprotonated forms of nickel(II) complex with N-salicylidene-N'-(2-phenylimidazol-4-ylmethylidene)-1,3-propanediamine, 1 and 1′, were synthesized and characterized. The X-ray crystal structures of 1-H₂O and 1′ were determined: 1-H₂O, P2₁/n (No. 14), a= 11.642(2), b= 12.908(3), c = 15.264(2) A, β = 96.642(1)°; 1′, I4₁,/a (No. 88), a = 22.651(3), c = 13.950(7) A. The crystal of 1-H₂O assumes a dinuclear structure bridged by the di-μ-phenoxo moiety in an out-of-plane fashion with Ni-Ni = 3.173(1) A and Ni-O = 2.126(3) A of the Ni₂O₂ core and two perchlorate ions as counter anions, in which the nickel(II) ion assumes an octahedral coordination geometry with N₃O₃ donor atoms consisting of four donor atoms of a quadridentate ligand, a bridging phenoxo-oxygen atom, and an oxygen atom of methanol. A ferromagnetic interaction with J = +7.1 cm^-1 operates between the two high-spin nickel(II) ions. 1 undergoes a deprotonation of the imidazole proton under basic conditions to give the deprotonated complex 1′. The crystal of 1′ consists of an electrically-neutral imidazolate-bridged cyclic-tetranuclear molecule with Ni-Ni = 6.339(2) A and Ni-N = 2.051(7) A, in which the nickel(II) ion assumes a square-pyramidal geometry with N₄O donor atoms consisting of the quadridentate ligand and an imidazolate nitrogen of the adjacent nickel (II) complex. An antiferromagnetic interaction with J= -6.3 cm^-l is observed between the adjacent nickel(II) ions through the imidazolate group. Since the corresponding deprotonated copper(II) complex with the same ligand assumed an imidazolate-bridged zigzag-chain structure, the result with the nickel(II) complex demonstrates a very marked influence of the metal ion on the formation of the assembly structure.