Department of Theoretical Chemistry, Chemical Center, P.O.B. 124, 22100 Lund, Sweden.
Chemistry. 2010 Jan 4;16(1):270-5. doi: 10.1002/chem.200902310.
Quasi-relativistic Douglas-Kroll CASPT2 calculations are reported for the title molecules, mainly to provide primary data for a fit of double-bond covalent radii. Indeed, a well-developed sigma(2)pi(2) double bond is identified in all cases. For Eu and Yb, however, it is an excited state. The main valence orbitals of all Ln ions are 6s and 5d. In the sigma bonds, more 5d than 6s character is found at the Ln. The Ln=C bond lengths show a systematic lanthanide contraction of 13 pm from La to Lu. An agostic symmetry breaking is demonstrated for Ce but its effect on the Ln-C length is small.
报道了标题分子的准相对论 Douglas-Kroll CASPT2 计算，主要为双键共价半径拟合提供原始数据。事实上，在所有情况下都确定了一个发育良好的 sigma(2)pi(2)双键。然而，对于 Eu 和 Yb，它是一个激发态。所有 Ln 离子的主要价轨道是 6s 和 5d。在 sigma 键中，Ln 处发现更多的 5d 而不是 6s 特征。Ln=C 键长从 La 到 Lu 呈现出 13 pm 的系统镧系收缩。证明了 Ce 的螯合对称性破缺，但对 Ln-C 长度的影响很小。
