Study on the intramolecular transannular chalcogentin interactions in dithiastannecine compounds.

Dithiastannecine compounds of the type [{D(C6H4CH2S)2}SnR1R2] with different donor atoms D were prepared, where D = O and R1 = R2 = Ph (4a); R1 = Ph, R2 = Cl (5a); R1 = n-Bu, R2 = Cl (6a); D = S and R1 = R2 = Ph (4b); R1 = Ph, R2 = Cl (5b); R1 = n-Bu, R2 = Cl (6b). The molecular structures of the monochloro compounds 5a, 5b, 6a, and 6b were established by single-crystal X-ray diffraction and exhibit trigonal bipyramidal geometry at the tin atom with different degrees of distortion being due a D?Sn interaction. The spiro compounds [{D(C6H4CH2S)2}2Sn] with D = O (7a) and D = S (7b) were also synthesized and structurally characterized; the molecular structure of 7a showed the tin atom with a bicapped tetrahedral geometry. The behavior of all tin compounds in solution was investigated by NMR spectroscopy revealing that the D?Sn interaction in solution was practically absent on the basis of the NMR chemical shifts values. DFT calculations with ADF package using VWN/QZ4P were carried out for the 6a and 6b compounds and showed that, in the topological analysis, bond critical points are present along the D?Sn direction.