Alkaline earth metal di- and triphenylmethanides: Analysis of ion association modes

A family of alkaline earth metal di- and triphenylmethanides was prepared and examined to illustrate ion association trends and associated reactivity in dependence of metal, coligand and ligand delocalization. To this effect, we are reporting the contact molecules Ba(18-crown-6)(CHPh2)2 and Ba(dme)2(CHPh2)2 (DME, 1,2-dimethoxyethane), the dissociated ions [Ba(hmpa)6][R]2, R = CHPh2, CPh3 (HMPA, hexamethylphosphoramide), in addition to two compounds with one metal bound anion, and an unassociated one, [Ca(18-crown-6)(N(SiMe3)2)][R], R = CHPh2, CPh3. We are also reporting a highly unusual lithium enolate, [Li2(OCHCH2)(pmdta)2][CHPh2] (PMDTA, N,N,N′,N″,N″-pentamethyldiethylenetriamine), obtained en route to the target compounds via THF scission chemistry.