Department of Chemistry, Swedish University of Agricultural Sciences, P.O. Box 7015, SE-750 07 Uppsala, Sweden.
Inorg Chem. 2010 May 17;49(10):4420-32. doi: 10.1021/ic100034q.
The structures of the N,N'-dimethylpropyleneurea (dmpu) solvated lanthanoid(III) ions have been studied in dmpu solution (La-Nd, Sm-Lu) and in solid iodide salts (La-Nd, Sm, Gd-Lu) by extended X-ray absorption fine structure (EXAFS), and single crystal X-ray diffraction (La, Pr, Nd, Gd, Tb, Er, Yb, and Lu); the EXAFS studies were performed on both K and L(III) absorption edges. Because of the space-demanding properties of dmpu upon coordination, dmpu solvated metal ions often show coordination numbers lower than those found in corresponding hydrates and solvates of oxygen donor solvents without steric requirements beyond the size of the donor atom. All lanthanoid(III) ions are seven-coordinate in solution, except lutetium(III) which is six-coordinated in regular octahedral fashion, whereas in the solid iodide salts the dmpu solvated lanthanoid(III) ions are all six-coordinate in regular octahedral fashion. A comparison of Ln-O bond lengths in a large number of lanthanoid(III) complexes with neutral oxygen donor ligands and different configurations shows that the metal ion-oxygen distance is specific for each coordination number with a narrow bond distance distribution. This also shows that the radius of the coordinated oxygen atom in these compounds can be assumed to be 1.34 A as proposed for coordinated water, while for ethers such as tetrahydrofuran (thf) it is somewhat larger. Using this atomic radius of oxygen in coordinated water molecules, we have calculated the ionic radii of the lanthanoid(III) ions in four- to nine-coordination and evaluated using the bond lengths reported for homo- and heteroleptic complexes in oxygen donor solvates in solution and solid state. This yields new and revised ionic radii which in some instances are significantly different from the ionic radii normally referenced in the literature, including interpolated values for the elusive promethium(III) ion.
N,N'-二甲基丙烯脲（dmpu）溶剂化镧系（III）离子的结构已通过扩展 X 射线吸收精细结构（EXAFS）和单晶 X 射线衍射（La、Pr、Nd、Gd、Tb、Er、Yb 和 Lu）在 dmpu 溶液（La-Nd、Sm-Lu）和固态碘化物盐（La-Nd、Sm、Gd-Lu）中进行了研究；EXAFS 研究分别在 K 和 L（III）吸收边缘进行。由于 dmpu 在配位时对空间的要求，dmpu 溶剂化金属离子的配位数通常低于相应的水合和无空间位阻氧给体溶剂的溶剂化物中的配位数，而氧给体原子的尺寸之外没有空间位阻。除了以规则八面体方式六配位的镥（III）离子外，所有镧系（III）离子在溶液中均为七配位，而在固态碘化物盐中，dmpu 溶剂化镧系（III）离子均以规则八面体方式六配位。大量具有中性氧给体配体和不同构型的镧系（III）配合物的 Ln-O 键长比较表明，金属离子-氧距离对于每个配位数都是特定的，并且具有狭窄的键距分布。这也表明，在这些化合物中，配位氧原子的半径可以假定为 1.34A，就像配位水一样，而对于醚类，如四氢呋喃（thf），它的半径则稍大。使用配位水分子中的这种氧原子原子半径，我们计算了四至九配位的镧系（III）离子的离子半径，并使用在溶液和固态氧给体溶剂化物中的同系物和杂系物的报告键长进行了评估。这产生了新的和修订的离子半径，在某些情况下，与文献中通常参考的离子半径有显著差异，包括难以捉摸的镨（III）离子的插值值。
