Theoretical study of donor-acceptor ability of borazine, alumazine, and boraphosphinine

Donor-acceptor complexes of borazine, alumazine, and boraphosphinine were studied by a quantum-chemical method. Structural and thermodynamic characteristics of complexes with Lewis acids (BCl3 and AlCl3) and bases (NH3 and pyridine Py) were calculated by the B3LYP method with the TZVP basis set. Energies of donor-acceptor bonds and energies of reorganization of donors, acceptors, and heterocycles upon the complex formation were found. Analysis of the energy variations occurring at the complex formation has shown that the reorganization energies of acceptors (BCl3 and AlCl3) and heterocycles play a key role in the complex stabilizations, whereas the reorganization energies of donors (NH3 and Py) are small and do not bring essential contribution to the complex-formation energy. The stability of donor-acceptor complexes decreases in the sequence alumazine > boraphosphinine > borazine. High alumazine reactivity toward chlorine atoms of the acceptor molecules BCl3 and AlCl3 was noted.