Introducing an unsymmetric and monoanionic N,N′,O-ligand with a tautomerizable backbone that chelates to magnesium in a heteroscorpionate-like fashion

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Heteroscorpionates have proved to be a versatile tridentate ligand class with applications in coordination chemistry, catalysis, and biomimetics. However, their fully unsymmetric variants with three distinct donors are rare and synthetically arduous. We report here a potentially tridentate N,N',O-monoanionic ligand (L) featuring an imine, an imidazole, and a phenolate as the donors, all originating from a central C1 unit, and obtained directly as the K salt [(L)K] via a compelling synthetic route. The L in [(L)K] shows an imine-enamine tautomerization in THF. However, a salt metathesis with MeMgI gives [(L)MgMe], where L exclusively adopts its imine form and facially κ3-chelates to magnesium in a totally unsymmetric heteroscorpionate-like fashion. As a preliminary application, both [(L)K] and [(L)MgMe] are successfully tested as active catalysts for the cyclotrimerization of aryl isocyanates under ambient conditions with the potassium complex showing better activity.