Dinuclear Nickel(II) Complexes of an Unsymmetric "End-Off" Compartmental Ligand: Conversion of Urea into Cyanate at a Dinuclear Nickel Core

Syunsuke Uozumi, Hideki Furutachi, Masaaki Ohba, Hisashi Okawa, David E. Fenton, Kenji Shindo, Susumu Murata, David J. Kitko

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Abstract

A phenol-based "end-off" compartmental ligand, 2-[N,N-di(2-pyridylniethyl)aminomethyl]-6-{N-[2-(dimethyl-amino)ethyl] iminomethyl}-4-methylphenol (HL), having an iminic bidentate and an aminic tridentate chelating arms on the 2- and 6-positions of the phenolic ring, respectively, forms dinuclear nickel complexes [Ni2(L)-(AcO)(NCS)2] (1), [Ni2(L)(AcO)2(MeOH)]PF6 (2), and [{Ni2(L)(OH)(MeOH)}2(CO3)](PF6) 2 (3). Complex 1 crystallizes in the monoclinic space group P21/c, a = 14.165(5) Å, b=15.198(4) Å, c = 17.395(8) Å, β= 100.62-(4)°, V = 3680(2) Å3 and Z = 4. The pair of Ni ions present are bridged by the phenolic oxygen of L- and an acetate group in syn-syn mode (Ni-Ni: 3.373(3) Å). An isothiocyanate nitrogen atom coordinates to each Ni providing an asymmetric dinuclear core with a mixed {5/6} coordination number set. Complex 2 crystallizes in the monoclinic space group P21/c a = 13.505(5) Å, b = 12.028(4) Å, c = 22.774(9) Å, β= 103.78(3)°, V = 3592(2) Å3, and Z = 4. It has a dinuclear core bridged by the phenolic oxygen of L- and two acetate groups in syn-syn mode, providing a μ-phenoxo-bis(μ-carboxylato)dinickel(II) core (Ni-Ni: 3.396(6) Å). A methanol molecule coordinates to the Ni bound to the bidentate arm, forming a dinuclear core having a {6/6} coordination number set and an asymmetric donor atom environment. Complex 3 crystallizes in the orthorhombic space group Pbcn, a = 19.056(5) Å, b = 18.997(4) Å, c = 19.919(6) Å, α = β= γ = 90°, V = 7211(5) Å3, and Z = 8. In each dinuclear unit a pair of Ni ions are bridged by the phenolic oxygen of L- and a hydroxo oxygen (Ni-Ni: 3.087(2) Å). A carbonate further bridges two of the dinuclear units to present a composite dimer. The Ni bound to the bidentate arm attains six-coordinate geometry by further interaction with two oxygens of the bridging carbonato group. The Ni bound to the tridentate arm assumes six-coordinate geometry by further coordination of a methanol oxygen. Complexes 1-3 react with urea in ethanol to form the isocyanate complexes [Ni2(L)-(AcO)(NCS)(NCO)] (1′), [Ni2(L)(AcO)(NCO)(EtOH)]PF6 (2′), and [{Ni2(L)(NCO)(EtOH)}2(CO3)](PF6)2 (3′), respectively. Complex 3′ crystallizes in the triclinic space group P1̄, a = 20.072(7) Å, b = 21.145(6) Å, c = 18.688(6) Å, α = 106.20(2)°, β= 90.01(3)°, γ = 88.73(3)°, V = 7614(4) Å3, and Z = 4. It has a dimeric structure very similar to that of 3, except for the replacement of the hydroxy bridge and the methanol ligand in 3 by isocyanate bridge and ethanol ligand, respectively, in 3′.

Original languageEnglish
Pages (from-to)6281-6287
Number of pages7
JournalInorganic chemistry
Volume37
Issue number24
Publication statusPublished - Dec 1 1998

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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