Syntheses, structures, magnetic, and spectroscopic properties of cobalt(II), nickel(II) and zinc(II) complexes containing 2-(6-methyl)pyridyl-substituted nitronyl and imino nitroxide

Y. Yamamoto, T. Suzuki, S. Kaizaki

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Abstract

Chelate complexation of 4,4,5,5-tetramethyl-2-(6-methyl-2-pyridyl)imidazolin-1-oxyl 3-oxide (NITmepy) and 4,4,5,5-tetramethyl-2-(6-methyl-2-pyridyl)imidazolin-1-oxyl (IMmepy) to cobalt(II) chloride (bromide) or zinc(II) chloride a3orded tetrahedral four-co-ordinate (T -4) complexes, [MX2(NITmepy)] and [MX2(IMmepy)] (MX=CoCl (1 and 2), CoBr (1Br and 2Br) or ZnCl (3 and 4), respectively) containing either a six- or afive-membered chelate ring as determined by single-crystal X-ray analysis. The formation of such T -4 complexes arises from the steric requirements of the methyl group at the o-position of the pyridyl-N donor. The UV-vis-NIR spectra suggest that both complexes 1 and 2 in dichloromethane retain their solid state structure. In acetonitrile, however, 1 exists as an equilibrium mixture due to dissociation of the co-ordinated NITmepy, while 2 is stable. The ligand-field spin-allowed and spin-forbidden d-d transitions of 1 and 2 are not influenced by the coordinated radical ligands. The reaction of nickel(II) chloride and thiocyanate with IMmepy gave a dichloro-bridged dinuclear complex with a square pyramidal five-co-ordinate (SPR-5) geometry and an OC-6 complex, respectively, [{NiCl(IMmepy)}2(μ-Cl)2] (5) and [Ni(NCS)2(IMmepy)2] (6). The intramolecular magnetic interactions in 1 and 2 are estimated to be antiferromagnetic, whereas 5 and 6 give ferromagnetic interactions. Complex 3, with one-dimensional columns, forms a dimer so that a moderate intermolecular antiferromagnetic coupling is demonstrated, while complex 4 exists as a discrete molecule in the crystal and shows paramagnetic behaviour.

Original languageEnglish
Pages (from-to)2943-2950
Number of pages8
JournalJournal of the Chemical Society, Dalton Transactions
Issue number19
DOIs
Publication statusPublished - Jan 1 2001

ASJC Scopus subject areas

  • Chemistry(all)

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