Versatility of coordination modes of N’-(pyridin-2-ylmethylene)picolinoylhydrazidate in the mononuclear cobalt(III) and polynuclear cobalt(II) complexes

Daniel K. B. Acheampong, Kei Kirihara, Rina Ogawa, Yukinari Sunatsuki, Takayoshi Suzuki

Research output: Contribution to journalArticlepeer-review

Abstract

Molecular and crystal structures of the mononuclear cobalt(III) complexes bearing N’-(pyridin-2-ylmethylene)picolinoylhydrazidate (Lpy), [Co(Lpy)3] (1) and [Co(Lpy)2]BF4 (2a and 2b), as well as those of the Lpy-bridged CoIII2CoII trinuclear and CoII4 tetranuclear complexes, [Co3(Lpy)4(H2O)2](BF4)4 (3) and [Co4(Lpy)4Cl2(CH3CN)2](BF4)2 (4), were determined by the single-crystal X-ray diffraction method, which revealed a variety of coordination and bridging modes of the multidentate Lpy ligand. The protonated free hydrazone, HLpy, exists as an E-form (in regard to the imine configuration) in the solid state and in solution. In the mononuclear CoIII complexes, the hydrazonate anion (Lpy) coordinates to a CoIII center in three different coordination modes: a bidentate κ2N1,N2 mode with the E-form (in 1) and two kinds of tridentate modes with the respective configuration, Z-κ3N1,N2,N4 and E-κ3O,N3,N4, in 2a and 2b. The former tridentate mode was sterically favored in the CoIII complexes, resulting in the five- and six-membered chelate rings, with a conversion of the imine configuration during the complexation. Complex 2a could also serve as a complex ligand toward a CoII ion with the κ2O,N3 mode, forming the CoIII–CoII–CoIII trinuclear complex (3). In the novel tetranuclear CoII complex (4), the E-Lpy hydrazonates bridged two CoII ions in two different modes: μ-κ2O,N13O,N3,N4 and μ-κ2N1,N23O,N3,N4, where all chelate coordinations formed a five-membered ring with the CoII ion.

Original languageEnglish
Article number120464
JournalInorganica Chimica Acta
Volume525
DOIs
Publication statusPublished - Sep 24 2021

Keywords

  • Bridging structures
  • Configurational isomers
  • Coordination modes
  • Picolinoylhydrazone

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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