Bajnóczi Eva G, Pálinkó István, Körtvélyesi Tamás, Bálint Szabolcs, Bakó Imre, Sipos Pál, Persson Ingmar
Department of Inorganic and Analytical Chemistry, University of Szeged, H-6720 Dóm tér 7., Szeged, Hungary.
Dalton Trans. 2014 Dec 14;43(46):17539-43. doi: 10.1039/c4dt02757d.
The identity of the predominating lead(ii) species in hyper-alkaline aqueous solution has been determined by Raman spectroscopy, and ab initio quantum chemical calculations and its structure has been determined by EXAFS. The observed and calculated Raman spectra for the Pb(OH)3 complex are in agreement while they are different for two-coordinated complexes and complexes containing Pb[double bond, length as m-dash]O double bonds. Predicted bond lengths are also consistent with the presence of Pb(OH)3 and exclude the formation of Pb[double bond, length as m-dash]O double bond(s). These observations together with experimentally established analogies between lead(ii) and tin(ii) in hyper-alkaline aqueous solutions suggest that the last stepwise hydroxido complex of lead(ii) is Pb(OH)3. The Pb-O bond distance in the Pb(OH)3 complex as determined is remarkably short, 2.216 Å, and has low symmetry as no multiple back-scattering is observed. The Pb(OH)3 complex has most likely trigonal pyramidal geometry as all reported three-coordinated lead(ii) complexes in the solid state. From single crystal X-ray data, the bond lengths for O-coordinated lead(ii) complexes with low coordination numbers are spread over an unusually wide interval, 2.216-2.464 Å for N = 3. The Pb-O bond distance is at the short side and within the range of three coordinated complexes, as also observed for the trihydroxidostannate(ii) complex indicating that the hydroxide ion forms short bonds with d(10)s(2) metal ions with occupied anti-bonding orbitals.
通过拉曼光谱、从头算量子化学计算确定了高碱性水溶液中主要的铅（II）物种的身份，并通过扩展X射线吸收精细结构（EXAFS）确定了其结构。[Pb(OH)₃]⁻配合物的观察和计算拉曼光谱一致，而对于二配位配合物和含有Pb═O双键的配合物则不同。预测的键长也与[Pb(OH)₃]⁻的存在一致，并排除了Pb═O双键的形成。这些观察结果以及在高碱性水溶液中铅（II）和锡（II）之间通过实验建立的类比表明，铅（II）的最后一步氢氧根配合物是[Pb(OH)₃]⁻。所确定的[Pb(OH)₃]⁻配合物中的Pb - O键距离非常短，为2.216 Å，并且由于未观察到多重背散射，其对称性较低。[Pb(OH)₃]⁻配合物很可能具有与固态中所有报道的三配位铅（II）配合物一样的三角锥几何形状。从单晶X射线数据来看，低配位数的O配位铅（II）配合物的键长分布在一个异常宽的区间内，对于N = 3时为2.216 - 2.464 Å。Pb - O键距离处于较短一侧且在三配位配合物的范围内，对于三羟基锡（II）酸盐配合物也观察到了这一点，这表明氢氧根离子与具有占据反键轨道的d(10)s(2)金属离子形成短键。
