Jancsó A, Gajda T, Szorcsik A, Kiss T, Henry B, Vankó G, Rubini P
Department of Inorganic and Analytical Chemistry, University of Szeged, Hungary.
J Inorg Biochem. 2001 Jan 15;83(2-3):187-92. doi: 10.1016/s0162-0134(00)00179-3.
Equilibrium and spectroscopic (1H, 13C NMR and 119Sn Mössbauer) studies in aqueous solution are reported for dimethyltin(IV) complexes of 2-hydroxyhippuric acid (Sal-Gly). Below pH 4, oxygen-coordinated complexes MLH and ML are formed. In the pH range 5-8.5, the species MLH(-1), predominates at any metal-to-ligand ratio. The ligand exchange of this species is slow on the NMR time scale, which allows its structural characterization by NMR spectroscopy: the coordination polyhedron around the tin atom is distorted trigonal bipyramidal, with tridentate [O-,N-,COO-] coordination of Sal-Gly, involving two equatorial methyl groups. The NMR results reveal that the main cause of the distortion of the polyhedron is the large CH3-Sn-CH3 angle of 136+/-4 degrees. The presented results supplement the data available on the dimethyltin(IV)-promoted amide deprotonation of peptides, and provide further arguments for the fundamental role of the carboxylate as an anchoring group in this process.
报道了在水溶液中对二甲基锡（IV）与2-羟基马尿酸（Sal-Gly）配合物的平衡和光谱（1H、13C NMR和119Sn穆斯堡尔）研究。在pH值低于4时，形成了氧配位的配合物MLH和ML。在pH值范围为5 - 8.5时，物种MLH(-1)在任何金属与配体比例下均占主导。该物种的配体交换在NMR时间尺度上较慢，这使得可以通过NMR光谱对其结构进行表征：锡原子周围的配位多面体为扭曲的三角双锥，Sal-Gly以[O-、N-、COO-]三齿配位，涉及两个赤道甲基。NMR结果表明，多面体扭曲的主要原因是较大的CH3-Sn-CH3角，为136±4度。所呈现的结果补充了关于二甲基锡（IV）促进肽的酰胺去质子化的现有数据，并为羧酸盐在该过程中作为锚定基团的基本作用提供了进一步的论据。
