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.