Synthesis, X-ray diffraction, and density functional studies of tin(IV) compounds containing a pincer-type SNS ligand.

Pincer-type compounds of general formula [{C5H3N(CH2S)2}SnRHal] [Hal = Cl, R = n-Bu (1), Ph (2); Hal = Br, R = n-Bu (3)] were prepared by the reaction of the dithiol ligand {C5H3N(CH2SH)2} with a suitable organotin reagent. The molecular structures of the compounds were established by single-crystal X-ray diffraction and exhibit trigonal bipyramidal geometry at the tin atom with degrees of tbp distortion ranging from 75 to 81, being caused by a transannular N ? Sn interaction. The behavior of all tin compounds in solution was investigated by NMR spectroscopy revealing that the N ? Sn interaction in solution was present on the basis of the chemical shifts values. DFT calculations with Gaussian 09 using M06/DGDZVP were carried out for all compounds. The structural data of the total optimization agreed with the experimental results and the topological analysis indicated that bond critical points are present along the N ? Sn direction.