Syntheses, structures, and properties of Co(III) complexes derived from polypyridine ligands containing one carboxamido nitrogen donor

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• 作者：Raman K. Afshar ; Rajiv Bhalla ; John M. Rowland ; Marilyn M. Olmstead and Pradip K. Mascharak
• 关键词：Pentadentate polypyridine ligands ; Carboxamide group ; Co(III) complexes ; Nitric oxide
• 刊名：Inorganica Chimica Acta
• 出版年：2006
• 出版时间：1 September 2006
• 年：2006
• 卷：359
• 期：12
• 页码：4105-4113
• 全文大小：371 K

文摘

Four cobalt(III) complexes containing the polypyridine pentadentate ligands N,N-bis(2-pyridylmethyl)amine-N′-ethyl-2-pyridine-2-carboxamide (PaPy₃H), N,N-bis(2-pyridylmethyl)amine-N′-[1-(2-pyridylethyl)acetamide (MePcPy₃H), and N,N-bis(2-pyridylmethyl)amine-N′-(2-pyridylmethyl)acetamide (PcPy₃H), have been synthesized. All three ligands bind the Co(III) center in the same fashion with the exception of loss of conjugation between the carboxamide moiety and the pyridine ring in the latter two. The structures of [(PaPy₃)Co(OH)][(PaPy₃)Co(H₂O)](ClO₄)₃ · 3H₂O (1), [(PaPy₃)Co(NO₂)](ClO₄) · 2MeCN (2), [(MePcPy₃)Co(MeCN)](ClO₄)₂ · 0.5MeCN (3), and [(PcPy₃)Co(Cl)](ClO₄) · 2MeCN (4) have been determined. These ligands with strong-field carboxamido N donor stabilize the +3 oxidation state of the Co center as demonstrated by the facile oxidation of the corresponding Co(II) complexes (prepared in situ) by H₂O₂, [Fe(Cp)₂](BF₄), or nitric oxide (NO). The Co–N_amido bond distances of 1–4 lie in the narrow range of 1.853–1.898 Å. ¹H NMR spectra of these complexes confirm the low-spin d⁶ ground states of the metal centers.