A preference for heterolepticity - Schlenk type equilibria in organometallic beryllium systems.

The reactions of beryllium halides with diphenyl beryllium were investigated in the N- and O-donor solvents NEt3 and THF, as well as in benzene and dichloromethane in the presence of the Lewis basic ligands THF, NEt3 and N-heterocyclic carbenes with various steric demand. In all cases the selective formation of heteroleptic beryllium Grignard compounds of the general formula [(L)1-2BePhX]1-2 (X = Cl, Br, I; L = C-, N-, O-donor ligand) was observed. The stability of these complexes was investigated computationally, while the differences between homo- and heteroleptic systems were also evaluated NMR spectroscopically and with single crystal X-ray diffraction. Mechanistic studies on the formation and speciation of these beryllium Grignard complexes in solution were performed.