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.

Three different ion association modes are observed in a family of elusive, highly reactive heavy alkaline earth di- and triphenylmethanides depending on the ligand, metal and co-ligand present. This study is elucidating factors that lead to the observation of different association trends and aimed to connect structure and reactivity trends.Figure optionsDownload as PowerPoint slideHighlights
► A family of rare, highly reactive heavy alkaline di- and triphenylmethanides is reported.
► Ion association trends in the target compound were evaluated by introduction of various donors.
► Reactivity of the target compounds is predominantly influenced by metal coordinative saturation.