title: A square-planar tetracoordinate oxygen-containing Ti₄O₁₇ cluster stabilized by two 1,1'-ferrocenedicarboxylato ligands.
abstract: 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.
authors.affiliation: Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (USA) http://stoddart.northwestern.edu.
authors.forename: Zhichang
authors.initials: Z
authors.lastname: Liu
authors.forename: Juying
authors.initials: J
authors.lastname: Lei
authors.forename: Marco
authors.initials: M
authors.lastname: Frasconi
authors.forename: Xiaohu
authors.initials: X
authors.lastname: Li
authors.forename: Dennis
authors.initials: D
authors.lastname: Cao
authors.forename: Zhixue
authors.initials: Z
authors.lastname: Zhu
authors.forename: Severin T
authors.initials: ST
authors.lastname: Schneebeli
authors.forename: George C
authors.initials: GC
authors.lastname: Schatz
authors.forename: J Fraser
authors.initials: JF
authors.lastname: Stoddart
keywords: electrochemistry; ferrocene; oxido ligands; titanium-oxo clusters