Synthesis of copper(II) halide dimers with 2-amino-5-methylpyridine and serendipitous copper catalyzed synthesis of 3-bromo-2-ethyl-5-methyl-1H-pyrrolo[2,3-b]pyridine

• Published in: Journal of coordination chemistry Vol. 76; no. 7-8; pp. 930 - 945
• Main Authors: Chittim, Carina L., Faber, Kesli, Dickie, Diane A., Landee, Christopher P., Telfer, Shane G., Turnbull, Mark M.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 18.04.2023; Taylor & Francis Ltd
• Subjects: Acetonitrile; Antiferromagnetism; Chemical synthesis; Copper; Cu(II) Halides; Dimers; Magnetic measurement; magnetism; Oxidation; pyrrolopyridine; solvent oxidation; Solvents
• ISSN: 0095-8972; 1029-0389
• DOI: 10.1080/00958972.2023.2221773

Reaction of CuX 2 ·nH 2 O (X = Cl, n = 2; X = Br, n = 0) with 2-amino-5-methylpyridine (5MAP) in acetonitrile yielded [(5MAP) 2 CuX 2 ] 2 (1, Cl; 2, Br). The compounds are isomorphous and crystallize in the monoclinic space group P2 1 /n as bihalide bridged dimers. Variable temperature magnetic measurements show very weak exchange in the two compounds (-2.1(1) K) which may correlate with previously proposed magnetostructural correlations for bihalide bridged Cu(II) dimers. In attempts to prepare 2 in 2-butanone as solvent, [(3-Br-2-Et-5-Mepyrpy)(CH 3 CO 2 ) 4 Cu 2 ] (3) was serendipitously isolated (3-Br-2-Et-5-Mepyrpy = 3-bromo-2-ethyl-5-methyl-7H-pyrrolido[2,3-b]pyridinium). The bicyclic ligand was synthesized in situ by condensation of 5MAP with the solvent; the acetate ions were generated by copper(II) catalyzed Baeyer-Villiger oxidation of the solvent. A mechanism for the synthesis is proposed. The resulting Cu-paddlewheel compound exhibits strong (-400 K) antiferromagnetic interactions.