Past exam of the chemistry course of the year 4 of the natural sciences course of the University of Cambridge / 2022 / Paper 1 / 8 / a / iii / Solution

A dimer compatible with the donor count is an asymmetric Li${}_2$O${}_2$ ring. Both phosphoryl oxygen donors bridge both Li centers. The two enamide N donors bind to one Li, whereas both nitrogen donors of a single chelating TMEDA bind to the other Li:Each Li consequently has exactly two O and two N neighbors, as required. The two donor sets differ chemically, giving two ${}^7$Li resonances when the solid-state connectivity is retained in solution. One TMEDA per dimer also matches the stated half equivalent per Li. The hemisolvent stoichiometry must not be drawn as one TMEDA on every Li.