Neutral tricoordinated beryllium(0) compounds – isostructural to BH3 but isoelectronic to NH3

Abstract

The electronic structure and reactivity of neutral tricoordinated Be(0) compounds BeL₃, L = CO (1), NHC (2) and PMe₃ (3) are explored by quantum mechanical calculations. These BeL₃ complexes are found to be planar or nearly planar like electron deficient BH₃ but isoelectronic with NH₃ and possess three L→Be donor–acceptor bonds. The Be atom can be considered as sp²-hybridized with a lone pair in the highly diffused 2p_z-orbital in contrast to the sp³ hybridization in isoelectronic NH₃. Even though the lone pair on Be is stabilized through π-back donation or hyperconjugative interaction with the ligands, yet it is highly reactive towards Lewis acids such as H⁺, BH₃ and W(CO)₅. The calculated gas phase protonation energies reveal that the NHC complex 2 and the trimethylphosphine complex 3 are ‘super basic’ in nature. Promising ligand property of BeL₃ has also been noted with BH₃ and transition metal fragment W(CO)₅. Besides, the reactivity of 2 and 3 is found to be more as compared to 1.