Department of Civil & Environmental Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3109, USA.
Phys Chem Chem Phys. 2018 May 9;20(18):12727-12735. doi: 10.1039/c8cp01461b.
The identity and structure of tin(ii)-fluoride complexes formed in aqueous solutions is determined by combining X-ray absorption spectroscopy, thermodynamic modeling and quantum mechanical calculations. Spectroscopic measurements confirm the presence of 3 stannous fluoride complexes, SnF+, SnF02 and SnF3-, with mean Sn-F bond distances that increase linearly, from 1.98 to about 2.04 Å, as a function of the coordination number. Computational ab initio calculations indicate that the stannous fluoride complexes form localized σs-p bonds, with the stereochemically active lone pair of the Sn(ii) atom distorting the geometry of the complexes. In addition, the SnF3- complex exhibits loosely coordinated water, which is removed upon addition of glycerol to lower the solvent activity. Our results provide spectroscopic confirmation of the stannous fluoride complexes proposed in the literature, and explain why glycerol additions stabilize solutions of Sn(ii) against oxidation.
采用 X 射线吸收光谱、热力学建模和量子力学计算相结合的方法，确定了在水溶液中形成的锡（II）-氟化物配合物的结构。光谱测量证实存在 3 种二价锡氟化物配合物 SnF+、SnF02 和 SnF3-，其平均 Sn-F 键距离随着配位数的增加从 1.98 线性增加至约 2.04 Å。从头算计算表明，二价锡氟化物配合物形成局域 σs-p 键，Sn（II）原子的立体活性孤对电子使配合物的几何形状发生畸变。此外，SnF3-配合物还表现出松散配位的水，当加入甘油以降低溶剂活度时，水被除去。我们的结果为文献中提出的二价锡氟化物配合物提供了光谱确认，并解释了为什么甘油的加入可以稳定 Sn（II）溶液防止氧化。
