A Square-Planar Tetracoordinate Oxygen-Containing Ti4O17 Cluster Stabilized by Two 1,1′-Ferrocenedicarboxylato Ligands


  • We thank Amy A. Sarjeant and Charlotte L. Stern for carrying out single-crystal and powder XRD analysis. In the Stoddart laboratory, this research is part (Project 34-944) of the Joint Center of Excellence in Integrated Nano-Systems (JCIN) at King Abdulaziz City of Science and Technology (KACST) and Northwestern University (NU). The authors would like to thank both KACST and NU for their continued support of this research. J.L. acknowledges the Chinese Scholarship Council for providing financial support during her stay at Northwestern University. M.F., X.L., and G.C.S. were supported by the Non-Equilibrium Energy Research Center (NERC), which is an Energy Frontier Research Center (EFRC) funded by the U.S. Department of Energy, Office of Basic Energy Sciences (DOE-BES) under Award DESC0000989. D.C. acknowledges the National Science Foundation for a Graduate Research Fellowship and the International Institute for Nanotechnology (IIN) at NU for a Ryan Fellowship. S.T.S. thanks the IIN at NU for an IIN Postdoctoral Fellowship.


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 [{Ti44-O)(μ2-O)2}(OPri)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 2px and 2py orbitals along with one perpendicular nonbonded 2pz 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.