1. University of Wyoming, Senior Honors Project, December 9, 2016
Iron Organometallics toward Olefin Metathesis and an Atomically-Precise Iron Oxide Nanocluster
Jonathan A. Kephart, Gaurab Rimal, Navamoney Arulsamy, Jinke Tang, Elliott B. Hulley*
University of Wyoming, Senior Honors Project, December 9, 2016

2. First Story: Organometallics
The properties of isolated metal atoms can be tuned through the coordination of an organic ligand framework.
Systematic modification of the ligand framework can establish catalytic activity for manipulation of organic substrates.
Organic – Compounds composed mostly of C, O, N, and H

3. Olefin Metathesis
Olefin Metathesis– Metal catalyzed scrambling of carbon- carbon double bonds (olefins)
Alkylidene – Metal-carbon double bond
Polymer Synthesis
General Mechanism
Pharmaceutical Synthesis

4. 2005 Nobel Prize in Chemistry
Yves Chauvin
Robert Grubbs
Richard Schrock
“for the development of the metathesis method in organic chemistry”

5. Metathesis Catalysts First-row Counterparts Benchmark Catalysts
Carbonyl ligands retract electron density from metal center
Iron-based alkylidenes only active to cyclopropanation
PROs: Excellent activity and/or selectivity
CONs: Based on toxic or expensive heavy metals

6. Metathesis and the Hulley Group
Use a bifunctional ligand platform with a pendent binding group (Nu) to stabilize the alkylidene.
Cyclopentadiene (Cp) and phosphine will provide a stable, electron-rich iron center.

7. Initial Synthetic Approach
Iron-Lithium Bimetallic Complexes
Furstner et al., J. Am. Chem. Soc. 2008, 130 (6),
Proposed Hydride
Signal

8. Subsequent Synthetic Work
Alkyl and Di-alkyl Iron Precursors
Fe(Np)2(TMEDA)
Fe(Np)Cl(TMEDA)
Fe(Nph)Cl(TMEDA)

9. Half-sandwich and Target Synthesis
Di-alkyl complexes are used to generate half-sandwich compounds.
With a half-sandwich iron alkyl complex in hand, the target catalyst is one step away.

10. Second Story: Iron Oxide Nanocluster
BULK vs. NANO: The properties of nano-scale and bulk materials are very different.
Bulk Gold:
Gold Nanoparticles:
A. Maeland and T. B. Flanagan, Can. J. Phys., 1964, 42, 2364.
Sun et al., J. Am. Chem. Soc. 2013, 135,
Surface Plasmon Resonance
Let’s take the nano-scale one step further…

11. Wan et al. Angew. Chem. Int. Ed. 2015, 54, 5977-5980.
Magic Number Clusters
Magic-Number Clusters – Small nanoparticles (<5 nm) that are stable with a specific number of atoms… atomically-precise and monodisperse… a magic number.
Wan et al. Angew. Chem. Int. Ed. 2015, 54,
Jin, R. Nanotechnol Rev , 31-56.
(left) Au25(SR)18
(right) Au25(PR3)10(SR)5Cl2
Buckminsterfullerene – C60
[Au23(PhC2)9(Ph3P)6]2+

12. Magic Number Iron Oxide
Using mass spectrometry, Sun et al. predicted the existence of Fe9O6 and Fe13O8.
They performed quantum chemical calculations to optimize core geometries.
Sun et al. Physical Review B 2000, 62,
Sun et al. Physical Review B 1999, 61,
Fe9O6
Mass Spectra
Fe13O8

13. Synthesis of Fe9O6(Np)6(TMEDA)3
Cluster was inadvertently synthesized and characterized via XRD while working with Fe(Np)2(TMEDA).
(Whoops!)
Fe9O6Np6(TMEDA)3

14. Crystalline State Rhombohedral Crystal Packing Cores and Voids
Asymmetric Unit: Fe2O(Np)(TMEDA)1/2

15. Solution-phase Magnetic Behavior
VT-NMR experiments were performed to probe the short-range temperature dependence of magnetic properties.
Solvent D8-toluene
Capillary D8-toluene
µeff,ave = 7.3 B.M.

16. Solid-state Magnetic Behavior
Solid-state magnetic analysis performed in collaboration w/ the Tang Group.
Fresh/Crystalline Sample
Old/Powder Sample
Spin Glass
Ferromagnet
spin glass behavior
paramagnetic behavior

17. Yang et al. Nat Communications 2013, 4, 2422.
Fe9O6 Future Work
Perform computational analysis of vibrations and electronic states
Assess utility as solid-state synthetic precursor or catalyst
Fully characterize magnetic/spectroscopic behavior
Roy, X. J. Am. Chem. Soc. 2014, 136, 16926−16931.
Yang et al. Nat Communications 2013, 4, 2422.

18. Thank You for Your Time!
Wild, Wonderful, Windy Wyoming