Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (USA) http://stoddart.northwestern.edu.
Angew Chem Int Ed Engl. 2014 Aug 25;53(35):9193-7. doi: 10.1002/anie.201402603. Epub 2014 Jul 2.
By introducing steric constraints into molecular compounds, it is possible to achieve atypical coordination geometries for the elements. Herein, we demonstrate that a titanium-oxo cluster [{Ti4(μ4-O)(μ2-O)2}(OPr(i))6(fdc)2], which possesses a unique edge-sharing Ti4O17 octahedron tetramer core, is stabilized by the constraints produced by two orthogonal 1,1'-ferrocenedicarboxylato (fdc) ligands. As a result, a square-planar tetracoordinate oxygen (ptO) can be generated. The bonding pattern of this unusual anti-van't Hoff/Le Bel oxygen, which has been probed by theoretical calculations, can be described by two horizontally σ-bonded 2p(x) and 2p(y) orbitals along with one perpendicular nonbonded 2p(z) orbital. While the two ferrocene units are separated spatially by the ptO with an Fe⋅⋅⋅Fe separation of 10.4 Å, electronic communication between them still takes place as revealed by the cluster's two distinct one-electron electrochemical oxidation processes.
通过在分子化合物中引入空间位阻，可以实现元素的非典型配位几何形状。在这里，我们证明了一个钛-氧簇 [{Ti4(μ4-O)(μ2-O)2}(OPr(i))6(fdc)2]，它具有独特的共享边 Ti4O17 八面体四聚体核心，由两个正交的 1,1'-二茂铁二羧酸根 (fdc) 配体产生的位阻稳定。结果，生成了一个平面四配位氧 (ptO)。通过理论计算探测到这种不寻常的反范特霍夫/勒贝尔氧的键合模式可以用两个水平 σ 键合的 2p(x)和 2p(y)轨道以及一个垂直非键合的 2p(z)轨道来描述。虽然两个二茂铁单元在空间上被 ptO 隔开，Fe⋅⋅⋅Fe 分离距离为 10.4 Å，但正如簇的两个独特的单电子电化学氧化过程所揭示的那样，它们之间仍然存在电子通信。
