Chelate [2-(Iminoethyl)pyridine N-oxide]metal Complexes - Synthesis and Structural Comparison with Their Chemically Related 2-(Iminoethyl)pyridine-Derived Systems

• Published in: European Journal of Inorganic Chemistry 2006-01, Vol.2006 (2), p.366-379
• Main Authors: Nienkemper, Katrin, Kotov, Vasily V., Kehr, Gerald, Erker, Gerhard, Fröhlich, Roland
• Format: Article
• Language: English
• Subjects: Chelates; Coordination chemistry; N,O ligands; O ligands; Transition metals
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.200500645

The N,O‐chelate ligands 2‐(iminoethyl)pyridine N‐oxide (2a) and 2‐(iminoethyl)‐6‐isopropylpyridine N‐oxide (2b) were prepared by conventional synthetic routes, the latter involving a variant of the Reissert–Henze reaction. Treatment of 2a with FeCl2 resulted in a deoxygenation reaction of the ligand and formation of the salt [bis{2‐(iminoethyl)pyridine}FeCl]+[FeCl4]– (18a). In contrast, the reaction of 2a with PdCl2 or CoCl2 cleanly furnished the six‐membered chelate [κN,O‐2(iminoethyl)pyridine N‐oxide]MCl2 complexes (19a, M = Pd) or (20a, M = Co), respectively, which were both characterised by X‐ray diffraction. Treatment of 2b with [NiBr2(dme)], followed by crystallisation from THF, gave the complex [(κN,O‐2b)NiBr2(THF)] (21b), which features a distorted trigonal‐bipyramidal coordination geometry of the central metal atom. The reaction of 2a with [NiBr2(dme)] gave the structurally related complex [(κN,O‐2a)NiBr2(κO‐2a)] (21a). The N,O‐chelate Pd complex 19a was shown to be an active catalyst for the Suzuki coupling reaction. The ligand systems 2a,b and their related 2‐(iminoethyl)pyridines 3a,b and a variety of metal complexes of ligands 3 were also prepared and characterised for comparison by X‐ray diffraction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)