Synthesis of organotin(IV) heterocycles containing a xanthenyl group by a Barbier approach via ultrasound activation: synthesis, crystal structure and Hirshfeld surface analysis.

A series of organotin heterocycles of general formula [{MeC(CHCH)O}SnR] [R = methyl (Me, 4), n-butyl (n-Bu, 5), benzyl (Bn, 6) and phenyl (Ph, 7)] was easily synthesized by a Barbier-type reaction assisted by the sonochemical activation of metallic magnesium. The Sn{H} NMR data for all four compounds confirm the presence of a central Sn atom in a four-coordinated environment in solution. Single-crystal X-ray diffraction studies for 17,17-dimethyl-7,7-diphenyl-15-oxa-7-stannatetracyclo[11.3.1.0.0]heptadeca-1,3,5(16),9(14),10,12-hexaene, [Sn(CH)(CHO)], 7, at 100 and 295 K confirmed the formation of a mononuclear eight-membered heterocycle, with a conformation depicted as boat-chair, resulting in a weak Sn...O interaction. The Sn and O atoms are surrounded by hydrophobic C-H bonds. A Hirshfeld surface analysis of 7 showed that the eight-membered heterocycles are linked by weak C-H...π, π-π and H...H noncovalent interactions. The pairwise interaction energies showed that the cohesion between the heterocycles are mainly due to dispersion forces.