Influence of intermolecular interactions on the Mössbauer quadrupole splitting of organotin(IV) compounds as studied by DFT calculations.

The influence of intermolecular interactions on the Mossbauer quadrupole splitting (A) of 119 Sn was investigated in detail by density functional theory (DFT) calculations. Six organotin(IV) complexes [Me 2 Sn(acac) 2 (1), Ph 3 SnCl (2), Me 3 Sn-succinimide (3), Me 3 Sn-phthalimide (4), Me 3 SnCl (5), and cHex 3 SnCl (6)] of known solid-state structures and quadrupole splittings were selected. Theoretical A values were calculated for both fully optimized geometries and experimental solid-state structures of different size, and the results were compared to the experimental A values. Compared to a synthetic procedure described in the literature for compound 4, a more convenient synthesis is reported here. The experimental A of this compound has also been redetermined at 80 K. For compounds with negligible intermolecular interactions in the solid state, calculated A values obtained did not vary significantly. In contrast, the calculated A values turned out to be very sensitive to the size of the supramolecular moiety considered in the crystal lattice. The crystal structure of compound 2 shows no significant intermolecular interactions; however, the calculated and the experimental A values remained very different, even when the supramolecular moiety considered was extended. Distortion of the coordination sphere of tin in the molecule of 2 toward a trigonal bipyramidal geometry was considered, and a possible weak intermolecular Sn···Cl interaction was included in the model. Steps of the distortion followed the new structure correlation function, which was found for the R 3 SnCl (R = alkyl, aryl) compounds. The experimental A value could be approached by this method. These results suggest that compound 2 is involved in some unexpected intermolecular interaction at 80 K.