Past exam of the chemistry course of the year 4 of the natural sciences course of the University of Cambridge / 2022 / Paper 2 / Section H / 32 / c / ii / Solution

F${}_2$ is an eight-membered ring with sequence $\mathrm{Cu}-\mathrm{N}-\mathrm{Li}-{\mathrm{C}}_{\mathrm{ipso}}-\mathrm{Cu}-\mathrm{N}-\mathrm{Li}-{\mathrm{C}}_{\mathrm{ipso}}$, closed back to the first Cu. Each N belongs to TMP; each ipso carbon belongs to a phenyl group. Each Cu is approximately linear between one TMP nitrogen and one phenyl ipso carbon. Each Li contacts a TMP nitrogen and the phenyl group bound to the other Cu, so the dimer is assembled head-to-tail rather than from two independent separated ion pairs.

G has the eight-membered sequence $\mathrm{C}{\mathrm{u}}_1-{\mathrm{N}}_1-\mathrm{L}{\mathrm{i}}_2-{\mathrm{N}}_2-\mathrm{C}{\mathrm{u}}_3-{\mathrm{N}}_3-\mathrm{L}{\mathrm{i}}_4-{\mathrm{C}}_{\mathrm{ipso}}$, closed to Cu${}_1$. The three N atoms belong to three TMP groups and the carbon belongs to the single phenyl group. Both copper sites remain approximately two-coordinate. The Li next to phenyl can also interact with its aromatic $\pi$ surface; this secondary contact need not have the same hapticity as in F${}_2$. The figure gives a connectivity projection, not idealized square bond angles or an X-ray metric reconstruction.