Coordination Chemistry and Spectroscopic Properties of Some Diorganotin(IV) Complexes with S-Donor Schiff Base Ligands

Abstract

Schiff bases S-benzyl- and S-methyl-β-N-(2-hydroxyphenyl)methylene dithiocarbazate (H₂L¹ and H₂L², respectively) and S-benzyl- and S-methyl-β-N-(2-chlorophenyl)methylenedithiocarbazate (HL³ and HL⁴, respectively) were prepared. Then organotin(IV) complexes [SnPh₂(L¹)] (1), [SnMe₂(L¹)] (2), [SnPh₂(L²)] (3), [SnMe₂(L²)] (4), [SnPh₂Cl(L³)] (5), and [SnPh₂Cl(L⁴)] (6) were obtained from the reaction of Schiff bases with SnR₂Cl₂ (R = Ph and Me). The synthesized complexes have been investigated by elemental analysis and IR, ¹H NMR, and ¹¹⁹Sn NMR spectroscopy. Spectroscopic studies show that, in complexes 1–4, the Schiff base acts as a tridentate dianionic ligand and coordinates through the thiol group, imine nitrogen, and phenolic oxygen. The coordination number of tin is five. In complexes 5 and 6, the ligand is monoanionic and unidentate, and coordinated only via the thiol group, and the azomethine nitrogen is not involved in coordination to tin. Therefore the coordination number of tin is four.

GRAPHICAL ABSTRACT      

Tris(dialkylamino)phosphine Chalcogenide Complexes of Tin(IV) Chloride: A Multinuclear (31P, 77Se,and 119Sn) NMR Characterization

Abstract

Four octahedral complexes of the type SnCl₄.2L [L = (R₂N)₃P(E): E = Se; R = Me(1), Et(2) and E = S; R = Me(3), Et(4)] have been studied in solution by multinuclear (³¹P, ⁷⁷Se, and ¹¹⁹Sn) NMR spectroscopy. ³¹P and ⁷⁷Se NMR data were informative of changes associated with complex formation. The solution structure of the complexes was confirmed by their ¹¹⁹Sn NMR spectra that showed two triplet features for each complex, attributed to a mixture of the expected cis and trans isomers. The triplet signal is due to the coupling with two equivalent phosphorus atoms, consistent with an octahedral geometry around the tin center. In addition, density functional theory (DFT)/B3LYP calculations have been carried out to support the interpretations of NMR data. The results are discussed and compared with those reported for related complexes.

GRAPHICAL ABSTRACT