Quantum-chemical calculations of spectroscopic, electric and thermochemical properties of some n-butyltin compounds

Some n-butyltin compounds were studied using DFT and semiempirical methods. The range of the investigated molecules covered various combinations of hydride, halide, alkoxy, carboxylate, and/or sulfonate substituents and at least one n-butyl group, all bonded to Sn(IV). The 119Sn and 1H chemical shifts were determined both in the gas phase and in chloroform, using the B3PW91//IGLO-II/III method and the PCM. It was found that the influence of chloroform on the 119Sn chemical shifts is small, which is in line with the non-coordinating and unreactive nature of this solvent. The gas-phase 119Sn chemical shifts were interpreted in terms of some group properties such as group electronegativity, hardness, and softness. For the majority of the investigated molecules, the group hardness correlates well with the δ(119Sn) values. Dipole moments, Sn-H vibrational frequencies, and thermochemical properties were calculated for five selected molecules, namely, n-Bu2SnHX (X = H, Cl, O2CMe, O3SMe) and n-Bu3SnH, by means of B3PW91 and B3LYP combined with two different mixtures of basis sets, as well as by means of the PM6 semiempirical method. It was shown that Gibbs free energy evaluated for the reaction of the homolytic cleavage of the Sn-H bond in these five molecules remains in line with their experimentally observed reactivity.