The Capacity of the R[OE(C6F5)2]2 (E = B, Al; R = C2H4, p-C6H4, m-C6H4) Complexes with Pyrazine and 3,3′-Bipyridine Towards Activation of Hydrogen Molecules

Abstract

Thermodynamic parameters of the process of dissociation of the donor-acceptor complexes of bidentate Lewis acids R[OE(C₆F₅)₂]₂ (E = B, Al; R = C₂H₄, p-C₆H₄, m-C₆H₄) with pyrazine (pyz) and 3,3′-bipyridine (bipy) have been determined by means of quantum-chemical simulation (M06-2X/def2-TZVP). A combination of the bidentate Lewis acid and the bidentate Lewis base may result in the formation of one or two donor-acceptor bonds. The formation of the hos-guest type complexes can be observed in the case of the formation of two donor-acceptor bonds. The non-optimal size of the donor and the acceptor molecules has led to the strain in the formed cyclic compound, which can be reflected in the possibility of the heterolytic rupture of hydrogen molecule (into the Н⁺ and Н^– ions), analogous to the Frustrated Lewis Pairs (FLP). The performed quantum-chemical simulations of the energy and thermodynamic parameters of the processes of activation of molecular hydrogen with the R[OE(C₆F₅)₂]₂·LB (E = B, Al; LB = pyz, bipy; R = C₂H₄, p-C₆H₄, m-C₆H₄) complexes in the gas phase have evidenced the prospects of further optimization of the size and acid-base properties of the bidentate donor and acceptor.