Past exam of the chemistry course of the year 4 of the natural sciences course of the University of Cambridge / 2022 / Paper 3 / Section E / 45 / a

Each primary amine arm of 2 condenses with one aldehyde 1, eliminating three waters overall and forming a tripodal tris(pyridylimine) ligand $L$. The three imine nitrogens and the three adjacent pyridine nitrogens chelate one Fe(II), giving $[\mathrm{Fe}L{]}^{2+}$, with three outward-facing terminal pyridines still free. The central tertiary amine is the tethering apex, not a seventh donor in the six-coordinate model.

The Fe coordination is approximately octahedral and is propeller-chiral: three bidentate chelates can have $\Delta$ or $\Lambda$ configuration. Achiral starting components and conditions give a racemic population unless a separate resolving influence is introduced. imine condensation and metal coordination cooperate in subcomponent self-assembly; the metal template selects the convergent ligand arrangement.