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

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

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

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

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

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.

Initial Synthetic Approach Iron-Lithium Bimetallic Complexes Furstner et al., J. Am. Chem. Soc. 2008, 130 (6), 1992-2004 Proposed Hydride Signal

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

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.

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, 16833-16836. Surface Plasmon Resonance Let’s take the nano-scale one step further…

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, 5977-5980. Jin, R. Nanotechnol Rev 1 2012, 31-56. (left) Au25(SR)18 (right) Au25(PR3)10(SR)5Cl2 Buckminsterfullerene – C60 [Au23(PhC2)9(Ph3P)6]2+

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, 8500-8507. Sun et al. Physical Review B 1999, 61, 5781-5785. Fe9O6 Mass Spectra Fe13O8

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

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

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.

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

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.

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