Penta- and heptacoordinated tin(IV) compounds derived from pyridine Schiff bases and 2-pyridine carboxylate: Synthesis and structural characterization

The synthesis of the Sn(IV)-complexed, Schiff base derivatives 1a–1l, prepared in one pot by the reaction of 2-amino-4-R-phenol (R = H, Me, Cl, NO2), 2-pyridinecarboxaldehyde, 2-picolinic acid and dimethyl-, dibutyl-, and diphenyltin oxides, is described. The complexes were characterized by IR, MS, 1H, 13C, 119Sn NMR. Suitable crystals of 1e and 1h enabled us to use X-ray diffraction to determine their molecular structures, which exhibited pentagonal–bipyramidal geometries where the butyl groups occupied the axial positions whereas the nitrogen and the oxygen atoms occupied the equatorial positions. The reaction of the Schiff base 2 with dibutyltin oxide led to the pentacoordinated complex, 2h, through the addition of methanol to the Cdouble bond; length as m-dashN bond. An unusual reduction–oxidation reaction took place by the reaction of 2-amino-4-nitro-phenol, dibutyltin oxide and 2-pyridinecarboxaldehyde, which produced the corresponding amine, 3h, and the amide, 4h, tin(IV) derivatives. Both structures were established by X-ray crystallography and exhibited a distorted, bipyramidal trigonal (BPT) geometry.