Department of Chemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Inorg Chem. 2011 Feb 7;50(3):1058-72. doi: 10.1021/ic1017714. Epub 2011 Jan 12.
The coordination chemistry of lead(II) in the oxygen donor solvents water, dimethylsulfoxide (dmso, Me(2)SO), N,N-dimethylformamide (dmf), N,N-dimethylacetamide (dma), N,N'-dimethylpropyleneurea (dmpu), and 1,1,3,3-tetramethylurea (tmu), as well as in the sulfur donor solvent N,N-dimethylthioformamide (dmtf), has been investigated by extended X-ray absorption fine structure (EXAFS) and/or large angle X-ray scattering (LAXS) in solution, and by single crystal X-ray diffraction and/or EXAFS of solid hydrates and solvates. Lead(II) may either form hemidirected complexes with large bond distance distribution and an apparent gap for excess electron density, or holodirected ones with a symmetric coordination sphere with normal bond distance distribution, depending on the strength of antibonding lead 6s/ligand np molecular orbital interactions and ligand-ligand interactions. The crystallographic data show that the solid lead(II) perchlorate and trifluoromethanesulfonate hydrate structures are hemidirected, while the solid lead(II) solvates of dma and dmpu have regular octahedral configuration with holodirected geometry and mean Pb-O bond distances in the range 2.50-2.52 Å. EXAFS data on the hydrated lead(II) ion in aqueous solution show broad bond distance distribution and a lack of inner-core multiple scattering contributions strongly indicating a hemidirected structure. The Pb-O bond distances found both by EXAFS and LAXS, 2.54(1) Å, point to a six-coordinate hydrated lead(II) ion in hemidirected fashion with an unevenly distributed electron density. The results obtained for the dmso solvated lead(II) ion in solution are ambiguous, but for the most part support a six-coordinate hemidirected complex. The mean Pb-O bond distances determined in dmf and dma solution by LAXS, 2.55(1) and 2.48(1) Å, respectively, indicate that in both solvate complexes lead(II) binds six solvent molecules with the former complex being hemidirected whereas the latter is holodirected. The dmpu and tmu solvated lead(II) ions have a regular holodirected octahedral configuration, as expected given their space-demanding characteristics and ligand-ligand intermolecular interactions. The dmtf solvated lead(II) ion in solution is most likely five-coordinate in a hemidirected configuration, with a mean Pb-S bond distance of 2.908(4) Å. New and improved ionic radii for the lead(II) ion in 4-8-coordination in hemi and holodirected configurations are proposed using crystallographic data.
本文研究了 Pb(II)在配位溶剂中的配位化学，这些溶剂包括水、二甲亚砜（dmso，Me(2)SO）、N,N-二甲基甲酰胺（dmf）、N,N-二甲基乙酰胺（dma）、N,N'-二甲基丙烯脲（dmpu）和 1,1,3,3-四甲基脲（tmu），以及配位硫溶剂 N,N-二甲基硫代甲酰胺（dmtf）。采用扩展 X 射线吸收精细结构（EXAFS）和/或大角度 X 射线散射（LAXS）在溶液中，以及单晶 X 射线衍射和/或固态水合物和溶剂化物的 EXAFS 进行了研究。Pb(II)可能形成具有大键距分布和明显过剩电子密度间隙的半直接复合物，或者形成具有对称配位球和正常键距分布的全直接复合物，这取决于反键 Pb 6s/配体 np 分子轨道相互作用和配体-配体相互作用的强度。晶体学数据表明，固态高氯酸铅和三氟甲烷磺酸盐水合物结构为半直接的，而固态 dma 和 dmpu 的铅(II)溶剂化物具有规则的八面体构型，具有全直接几何形状，Pb-O 键距在 2.50-2.52 Å 范围内。水溶液中 Pb(II)水合离子的 EXAFS 数据显示出宽的键距分布和缺乏内芯多次散射贡献，这强烈表明存在半直接结构。通过 EXAFS 和 LAXS 发现的 Pb-O 键距为 2.54(1)Å，表明 Pb(II)以半直接方式六配位，电子密度分布不均匀。在溶液中，dmso 溶剂化的 Pb(II)离子的结果存在一定的歧义，但大部分结果支持六配位的半直接配合物。通过 LAXS 确定的 dmf 和 dma 溶液中的平均 Pb-O 键距分别为 2.55(1)和 2.48(1)Å，表明在这两种溶剂配合物中，Pb(II)与六个溶剂分子结合，前者为半直接，后者为全直接。由于其空间要求特征和配体-配体分子间相互作用，dmpu 和 tmu 溶剂化的 Pb(II)离子具有规则的全直接八面体构型。在溶液中，dmtf 溶剂化的 Pb(II)离子可能是五配位的半直接构型，平均 Pb-S 键距为 2.908(4)Å。使用晶体学数据，提出了 Pb(II)在半直接和全直接构型的 4-8 配位中建议使用新的和改进的 Pb(II)离子半径。
