Selective imidazolidine ring opening during complex formation of iron(III), copper(II), and zinc(II) with a multidentate ligand obtained from 2-pyridinecarboxaldehyde N-oxide and triethylenetetramine

Citation
M. Boca et al., Selective imidazolidine ring opening during complex formation of iron(III), copper(II), and zinc(II) with a multidentate ligand obtained from 2-pyridinecarboxaldehyde N-oxide and triethylenetetramine, INORG CHEM, 39(15), 2000, pp. 3205-3212
Citations number
51
Categorie Soggetti
Inorganic & Nuclear Chemistry
Journal title
INORGANIC CHEMISTRY
ISSN journal
00201669 → ACNP
Volume
39
Issue
15
Year of publication
2000
Pages
3205 - 3212
Database
ISI
SICI code
0020-1669(20000724)39:15<3205:SIRODC>2.0.ZU;2-4
Abstract
The condensation of 2-pyridinecarboxaldehyde N-oxide and triethylenetetrami ne yields a product with two imidazolidine rings, as proven by a solid-stat e X-ray structure analysis as well as by NMR solution spectra. This ligand, L-1, undergoes a ring-opening reaction on complex formation with Cu(II), y ielding [CuL2](2+) where L-2 functions as a pentadentate ligand, containing only one imidazolidine ring. On complexation with Zn(II) and Fe(III), both rings are opened and the complexes [ZnL3](2+) and [FeL3](3+) with a hexade ntate L-3 ligand are formed. The recrystallization of [ZnL3](2+) from DMSO solution results in the complex [ZnL1(DMSO)(2)](2+) in which L-1 behaves as a tetradentate ligand. Thus L-1, L-2, and L-3 are structural isomers with two, one, or no imidazolidine rings, as confirmed by X-ray structure analys es. The intramolecular ring formation is the result of the nucleophilic add ition of the N(amino) group to the electrophilic sp(2)-hybridized -HCdelta=N site. Owing to the absence of the chelate effect on the sp(3)-hybridized carbon atom belonging to the imidazolidine ring, the ring opening is facil itated and readily observed upon complex formation with Cu(II), Zn(II), and Fe(III).