Synthesis of new dipyridinylamine and dipyridinylmethaneligands and their coordination chemistry with Mg(ii) and Zn(ii)

Abstract

Sterically hindered, symmetrically 2,2′-substituted bispyridylamines 1a–c and methylene-bispyridine 4 were prepared in a three-step procedure from commercially available 2,6-dibromopyridine, via a Cu-mediated alkylation followed by two consecutive Buchwald–Hartwig N-arylation reactions or two Negishi cross-coupling reactions, respectively, in the presence of Pd catalysts. Deprotonation of the NH and CH₂ bridge of 1a and 4, respectively, enables the formation of Zn(II) and Mg(II) complexes, whose structures have been determined by single-crystal diffraction studies and/or NMR spectroscopy. A magnesium–isopropyl complex stabilized by a bispyridyldiiminate ligand derived from 4 is shown to be an active catalyst for the isotactic polymerization of methyl methacrylate.