Structural differences in eight- and ten-membered heterocyclic tin compounds displaying transannular interactions O---Sn. An experimental and theoretical study.

Two series of heterocyclic tin compounds of general formula [(S{C6H3(CH2)nS}2O)SnR1R2] with different central ring sizes were prepared. The ten-membered series includes the compounds with n = 1 and R1 = R2 = Ph (5); R1 = Cl, R2 = Ph (6); R1 = Cl, R2 = n-Bu (7); R1 = R2 = Cl (8); the eight-membered series includes the compounds with n = 0 and R1 = R2 = Ph (10); R1 = Cl, R2 = n-Bu (11) and R1 = R2 = Cl (12). The compounds 5, 7, 8, 10, and 11 were investigated by single-crystal X-ray diffraction. The chloro compounds 7, 8, and 11 displayed a bipyramidal geometry at the tin atom with different degrees of distortion ranging from 57% to 62%. The diphenyl compounds 5 and 10 displayed a tetrahedral geometry at Sn. The conformation of the central ring in the ten-membered series is similar and is described as boat; the other series displayed two different conformations described as boatchair and boatboat. The possible conformers in the gas state of compounds 5, 7, 8, 10, 11, and 12 were investigated by MMFF, LSDA, BLYP, B3LYP, and M06 functionals using the DGDZVP and TZVP basis sets. The structural data of the total optimization agreed with the experimental results. The topological analysis indicated that bond critical points are present along the O?Sn direction in the compounds 7, 8, 11, and 12.