Iron coordination chemistry of N-(bis(2-pyridyl)methyl)pyridine-2-carboxamide

Shourong Zhu, William W. Brennessel, Roger G. Harrison, Lawrence Que

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44 Scopus citations

Abstract

The amidate function participates in the coordination chemistry of iron containing biomolecules such as the anti-tumor drug bleomycin and the enzyme nitrile hydratase. Our interest in amidate coordination prompted an investigation of the iron complexes of the potentially tetradentate ligand N-(bis(2-pyridyl)methyl)pyridine-2-carboxamide (H-L). A number of complexes have been isolated and structurally characterized, including [FeII(L)2] (1), [FeIII(L-OCH3)Br2(CH3OH)] (3), [Fe2III(μ-OH)2(L-OCH3) 2Br2] (4), and [Fe4III(μ-OCH3)2(L-O) 2Br6] (5). In these complexes L acts as a meridional tridentate ligand, as previously observed for the corresponding [Cu(L)Cl(CH3OH)] complex (Inorg. Chem. 39 (2000) 5326). In the cases of 3 and 4, the hydrogen of the tertiary carbon has been replaced by a methoxy group in the course of complex synthesis. In the case of 5, the tertiary hydrogen is replaced by hydroxide, and this oxygen and the dangling pyridine act as a bidentate ligand to a second iron ion. When the reaction of FeBr3 and H-L was carried out in acetonitrile in the presence of base but in the absence of air, the ligand was cleaved into two pieces, affording [FeIIBr2(pyridine-2-carboxamide)(di-2-pyridylketone)] (6). It is proposed that the coordination of the amide nitrogen of H-L to an iron(III) center as an amidate activates the α-C-H bond and results in the oxidation of the α-C-Namide bond to an imine.

Original languageEnglish (US)
Pages (from-to)32-38
Number of pages7
JournalInorganica Chimica Acta
Volume337
DOIs
StatePublished - Sep 26 2002

Keywords

  • Amidate complexes
  • Carboxamide complexes
  • Crystal structure
  • Iron complexes

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