Synthesis and characterization of a new chloro-di-phenyltin(IV) complex with 2-mercapto-nicotinic acid: Study of its influence upon the catalytic oxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase

The complex [(C6H5)2SnCl(HMNA)] (1) where H2MNA is thioamide 2-mercapto-nicotinic acid has been synthesized by reacting a methanolic solution of di-chloro-di-phenyltin(IV) Ph2SnCl2 with an aqueous solution of 2-mercapto-nicotinic acid, containing twofold amount of potassium hydroxide. The Sn/ligand molar ratio is 2:1. The complex was characterized by elemental analysis, FT-IR and Mössbauer spectroscopic techniques. In addition the crystal structure of the molecule was determined by an X-ray diffraction at 293(2) K. C18H14ClNO2SSn is monoclinic, space group P21/n, a = 15.089(3) Å, b = 15.846(3) Å, c = 16.691(3) Å, β = 105.57(3)°, Z = 8. The ligand coordinates to the metal center through the exocyclic sulfur and the heterocyclic nitrogen atoms, forming a four membered ring. The coordination sphere around the tin(IV) ion is completed with two carbon atoms from the two phenyl groups and one chlorine atom. The geometry around the tin atom can be described either as trigonal bipyramidal or tetragonal pyramidal. Finally, the influence of the complex [(C6H5)2SnCl(HMNA)] (1) upon the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX) was also kinetically and theoretically studied and the results compared with the ones of the corresponding binuclear complex [(C6H5)3Sn(MNA)Sn(C6H5)3 · (acetone)] (2) reported in the literature.