Thermodynamics of donor-acceptor interaction of BF3 and B(OC2H5)3 with nitrogen-containing ligands in tetrahydrofuran

Stability constants of BF3(I) complexes with benzimidazole (2), 2-methylbenzimidazole (3), 1-butylbenzimidazole (4), imidazole (5), n-butylamine (6), isoamylamine (7), piperidine (8), tret-butylamine (9), as well as enthalpy (Δ) of coordination process in tetrahydrofuran at 25 deg are determined using the calorimetric method. Proton-acceptor properties of ligands are characterized by pKsub(B) values found sectrophotom,etrically. ΔH values for processes of 2, 5, 8, 9 coordination to B(OC2H5)3 (10) are determined under the same conditions. The presence of linear correlations between pKsub(B) and thermodynamic parameters of the processes is established. Substitution of OC2H5 for F in 1 leads to essential reduction of acceptor properties of 10. A relaxation of solvation effect contribution into the determined ΔH values is observed