New diorganotin(IV) complexes of salicylaldehyde based hydrazones bearing furan heterocycle moiety: X-ray structural investigation of dimethyltin(IV) and diphenyltin(IV) complexes

Abstract

Some new diorganotin(IV) derivatives formulated as R2SnL (where R = Me, Bu, Ph and Oct) were obtained upon treatment of diorganotin(IV) precursors with acylhydrazones [H2La = N'-(2-hydroxy-3-methoxybenzylidene)furan-2-carbohydrazide, H2Lb = N'-(5-chloro-2-hydroxybenzylidene)furan-2-carbohydrazide and H2Lc = N'-(2-hydroxy-5-nitrobenzylidene)furan-2-carbohydrazide] derived from Schiff base condensation of furan-2-carbohydrazide and substituted salicylaldehydes in methanol in appropriate molar ratio. The enolic tridentate chelating mode of the acylhydrazones towards the diorganotin moieties [R2Sn(IV)]2+ was ascertained by micro-analysis and various spectroscopic techniques viz., Fourier-transform infrared (FT-IR), multinuclear (1H, 13C and 119Sn) magnetic resonance (NMR) and electrospray ionization mass (ESMS) spectrometry. The single crystal X-ray diffraction investigation of Me2SnLb and Ph2SnLb demonstrates that they crystallize in monoclinic space groups ‘P 21’ and ‘P 21/c’ respectively, and comprised of crystallographically discrete 2 and 4 molecules in their respective unit cells. Both mononuclear complexes adopt a highly distorted square-pyramidal geometry (SP) wherein the imine nitrogen preferably occupies the apical site whereas the more electronegative enolic and phenolic oxygen atoms of the ligand and two carbon atoms of the methyl/phenyl groups of the organotin(IV) moiety align themselves equatorially around the five-coordinated tin center in a square plane. Diorganotin(IV) derivatives were also analyzed in air by thermo-gravimetric (TG, DTG and DTA) techniques to elucidate their thermal stability and decomposition trends.