A Novel 2:3 Condensation Complex of Salicylaldoxime and Di-n-butyltin(IV) Oxide

Abstract

The crystal structure of the reaction product of the 2:3 condensation of salicylaldoxime with di-n-butyltin(IV) oxide, [(Bu2Sn)(Bu2SnO)(Bu2SnOH)(HONZO)(ONZO)], where HONZOH represents HON=CHC6H4OH (salicylaldoxime), was determined by single-crystal X-ray diffraction; it belongs to the monoclinic system, space group P2(1)/c, with a = 20.995(3) angstrom, b = 17.394(4) angstrom, c = 12.254(2) angstrom, beta = 94.43(2)degrees, and Z = 4. The compound contains two five-coordinate trigonal-bipyramidal tin atoms with the two butyl groups in equatorial positions; the third tin atom has a seven-coordinate pentagonal-bipyramidal geometry with the two butyl groups in apical positions. The bonds of the salicylaldoxime ligands to the metal atoms are inequivalent. Both ligands are bound to the seven-coordinate tin atom through the oxygen atom originating from the phenolic function and through the nitrogen atom of the aldoxime function. In the ligand that binds as HONZO, the phenolate oxygen atom further coordinates a five-coordinate tin atom. In the ligand that coordinates as ONZO, the NO oxygen is bonded to the other five-coordinate atom. The H-1, C-13, and Sn-119 NMR data are in agreement with such a structure existing as a major species M in solution. However, the NMR spectra also reveal the presence of three other minor species in solution, m1, m2, and m3. These species could not be isolated as pure compounds, as crystallization from any solution of this compound led systematically to crystals of M. The H-1 and Sn-119 spectra, the (n)j(Sn-119-Sn-119/Sn-117) coupling satellite patterns observed in Sn-119 spectra, and the two-dimensional proton detected H-1-Sn-119 heteronuclear multiple bond correlation (2D H-1-Sn-119 HMBC) maps allow us to propose a structure for each species.