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Divergent Organomagnesium Reactivity of Rigid, Dinucleating Naphthyridine Ligands: Backbone Changes with Big Impact
Errikos Kounalis1, Marieke M Broekman1, Puck Uyttewaal1
1Organic Chemistry and Catalysis, Institute for Sustainable and Circular Chemistry, Faculty of Science, Utrecht University, Universiteitsweg 99, Utrecht 3584 CG, The Netherlands.
Abstract:
We report the synthesis and characterization of two naphthyridine-based ligands bearing pendant secondary amine and amide donors, respectively. We additionally report their deprotonation chemistry and reactivity with dialkylmagnesium and Grignard reagents. The Grignard reactions yield structurally distinct LMg2Cl2·(THF) n complexes, with the amide-based complex exhibiting reduced steric strain from the ligand around the Mg2Cl2 core. Comparison of the steric profiles of the LMg2Cl2·(THF) n complexes reveals that this reduced steric strain stems from the difference in binding modes of the ligands, which in the amide case points the bulk of sterically demanding substituents away from the Mg2Cl2 core. Reactivity of the ligands with Mg-(n-Bu)2 shows divergent outcomes: the secondary amine-based ligand forms the LMg2(n-Bu)2·(THF)2 complex cleanly, whereas the amide-based ligand produces paramagnetic species via Mg-C homolysis, triggering radical reactivity that results in ligand butylation and dimerization. These findings underscore the unique steric and electronic features of dimagnesium complexes supported by rigid, dinucleating naphthyridine ligands, highlighting how variations in ligand architecture can profoundly influence coordination chemistry and reactivity.
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