Synthesis and characterization of tin complexes [Sn(L)Hal4] (L = N-alkyl-(pyridin-2-yl)aldimine; Hal = Cl, Br): A structural study

The reactions of the ligands N-methyl-(pyridin-2-yl)aldimine (a), N-ethyl-(pyridin-2-yl)aldimine (b), and N-benzyl-(pyridin-2-yl)aldimine (c) with SnCl4 and SnBr4 led to the formation of compounds [Sn{(C5H4N)HCNMe}Cl4] (1), [Sn{(C5H4N)HCNMe}Br4] (2), [Sn{(C5H4N)HCNEt}Cl4] (3), [Sn{(C5H4N)HCNEt}Br4] (4), [Sn{(C5H4N)HCNBn}Cl4] (5), and [Sn{(C5H4N)HCNBn}Br4] (6) in good yields. All the compounds were characterized by 1H, 13C{1H}, and 119Sn{1H} NMR, vibrational IR-Raman spectroscopy, elemental analyses, and X-ray diffraction analysis. The structural studies confirmed the formation of the respective six-coordinate tin complexes as a result of the chelation of the iminic and pyridinic nitrogen atoms of the ligands towards the tin atom; the Sn–N distances were shortened as the Lewis acid character at the tin atom was increased. In all the molecular structures the tin atom displayed a distorted octahedral local geometry.

Graphical abstractThe study of the hypercoordination in some tetrachloro and tetrabromotin complexes of general formula [Sn{(C5H4N)HCNR}Hal4] (R = Me, Et, Bn; Hal = Cl, Br) containing bidentate Schiff bases as ligands is reported. The enhancement of the Lewis acidity on the tin atom in the distorted octahedral tetrachlorotin complexes strengths the coordination of the bidentate ligands.Figure optionsDownload full-size imageDownload as PowerPoint slide