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Timothy P. Hanusa

Title and Contact Information

Professor of Chemistry
Office: 7864 SC
Phone: (615) 322-4667
Email

Education

Ph.D., Indiana University, 1983

Specialties

Organometallic Chemistry
Materials Chemistry
Inorganic Chemistry

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Hanusa

Research

Inorganic Chemistry

Use of ligand design to control the reactivity of main-group and transition metal organometallic and coordination complexes; investigation of steric effects on the reactivity and magnetic properties of metal complexes; synthesis of precursors to materials with desirable electronic/optical properties; computational investigation of bonding and structure in inorganic systems.

Molecular chemistry of the main-group metals: Our group has been developing ligand-based approaches to manipulating the structure and reactivity of main-group metals. The synthesis of volatile and/or liquid compounds that could be useful for the preparation of thin films of metal oxides and halides by chemical vapor deposition (CVD) methods is of particular interest. We have used large, sterically demanding cyclopentadienyl ligands to turn poly- or oligomeric compounds of the heavier alkaline-metals (Ca, Sr, Ba) into monomeric species, often dramatically lowering their sublimation temperatures or melting points. Aluminum alkoxides and alkyls are being designed to deposit stochiometrically precise films of alumina on silicon wafers for microelectronics applications.

Use of sterically bulky allyl ligands in catalysis and the study of non-covalent interactions: The compact size of the allyl anion ([C3H5]-) means that its transition metal complexes are often coordinatively unsaturated and prone to facile decomposition. We have used sterically bulky substituents (e.g., SiMe3) to produce pi-allyl transition metal compounds that have no unsubstituted analogues, such as the extremely electron deficient 12- and 14-electron species [1,3-(SiMe3)2C3H3]2Cr and [1,3-(SiMe3)2C3H3]2Fe. We are synthesizing new bis- and tris(allyl) metal complexes of the transition metals, and lanthanides and examining the way that the double bonds of allyl ligands can engage in cation-pi interactions. These non-covalent interactions are important in biological systems, but commonly involve aromatic rings. We are examining non-aromatic cation-pi interactions such as that between K+ the zincate complex at right. Our investigations are helping to identify the geometric features that can affect the strength of cation-pi attractions.  

Symmetryeffects on the magnetic properties of transition metal complexes: There is considerable interest in the synthesis of transition metal compounds whose magnetic properties can be influenced by external agents. In the case of spin-crossover complexes, transitions between high- and low-spin states can be induced by temperature, pressure, and light, and the effective control of such transitions could ultimately lead to applications in switching devices, magnetic storage, and photonic systems.

Metallocene-based complexes have been attractive in this regard, and variations in the metals, their oxidation states, and ring substituents have led to species displaying spin-crossover behavior, molecular ferromagnetism, and ferromagnetic/antiferromagnetic exchange. We have been studying bis(indenyl)metal complexes, which are relatives of metallocenes, but whose ligand conformations are sensitive to orbital occupancies.

Monomeric (1-RC9H6)2Cr (R = t-Bu, SiMe3) are staggered, high-spin complexes with 4 unpaired electrons. When additional bulk is added to the ligands (e.g., (1,3-R2C9H5)2Cr; R = t-Bu, SiMe3), however, rotation to a gauche (near 90)conformation is forced upon the molecule. Owing to increased metal-ligand orbital mixing, maintenance of the high-spin state is no longer possible, and the molecules adopt low-spin configurations with 2 unpaired electrons. This indicates that both steric bulk and electronic effects brought about by selective substitution of the indenyl ligand can be used to tailor the magnetic properties of the compounds, making them suitable as tunable sources of variable spin molecules. The spin state changes also suggest that there may be useful variations in the reactivity of the complexes, a possibility we are investigating.

Selected Publications

Boyde NC, Chmely SC, Hanusa TP, Rheingold AL, Brennessel WW. Structural Distortions in M[E(SiMe3)(2)](3) Complexes (M = Group 15, f-Element; E = N, CH): Is Three a Crowd? Inorganic Chemistry. 2014, 18 (53): 9703-9714.

Lichtenberg C, Spaniol TP, Peckermann I, Hanusa TP, Okuda J. Cationic, Neutral, and Anionic Allyl Magnesium Compounds: Unprecedented Ligand Conformations and Reactivity Toward Unsaturated Hydrocarbons. Journal of the American Chemical Society. 2013, 135 (2): 811-821.

Engerer LK, Carlson CN, Hanusa TP, Brennessel WW, Young VG. Sigma- vs pi-Bonding in Manganese(II) Allyl Complexes. Organomettallics. 2012, 31 (17): 6131-6138.

Jochmann P, Spaniol TP, Chmely SC, Hanusa TP, Okuda J. Preparation, Structure, and Ether Cleavage of a Mixed Hapticity Allyl Compound of Calcium. Organomettallics. 2011, 30 (19): 5291-5296.

Bierschenk EJ, Wilk NR, Hanusa TP. 2,4-Pentanediolate as an Alkoxide/Diketonate "Hybrid" Ligand and the Formation of Aluminum and Zirconium Derivatives. InOrganic Chemistry. 2011, 50 (23): 12126-12132.

Engerer LK, Hanusa TP. Geometric Effects in Olefinic Cation-pi Interactions with Alkali Metals: A Computational Study. Journal of Organic Chemistry. 2011, 76 (1): 42-49.

ChmelySC, Hanusa TP, Brennessel WW. Bis(1,3-trimethylsilylallyl)beryllium. Angewandte Chemie-International Edition. 2010, 49 (34): 5870-5874.

Quisenberry KT, White RE, Hanusa TP, Brennessel WW. Allyl complexes of the heavy alkaline-earth metals: molecular structure and catalytic behavior. New Journal of Chemistry. 2010, 34 (8): 1579-1584.

Schmidt BW, Rogers BR, Gren CK, Hanusa TP. Carbon incorporation in chemical vapor deposited aluminum oxide films. Thin Solid Films. 2010, 518 (14): 3658-3663.

Crisp JA, Meier RM, Overby JS, Hanusa TP, Rheingold AL, Brennessel WW. Indenyl Complexes of Manganese(II). Conformational Flexibility of the Manganese(II) (RnC9H7-n) Bond. Organometallics. 2010, 29 (10): 2322-2331.

Chmely SC, Hanusa TP. Complexes with Sterically Bulky Allyl Ligands: Insights into Structure and Bonding. European Journal of Inorganic Chemistry. 2010, 9: 1321-1337.

Schmidt BW, Sweet WJ, Bierschenk EJ, Gren CK, Hanusa TP, Rogers BR. Metal-organic chemical vapor deposition of aluminum oxide thin films via pyrolysis of dimethylaluminum isopropoxide. Journal of Vacuum Science & Technology A. 2010, 28 (2): 238-243.

Meredith MB, McMillen CH, Goodman JT, Hanusa TP. Ambient temperature imidazolium-based ionic liquids with tetrachloronickelate(II) anions. Polyhedron. 2009, 28 (12): 2355-2358.

Gren CK, Hanusa TP, Rheingold AL. Solvent-resistant structures of base-free lithium and potassium allyl complexes, M[(SiMe3)(n)C3H5-n] (M = Li, n=3; M = K, n=2). Main Group Chemistry. 2009, 8 (4): 225-235.

Hanusa T. Exploring the Relationships Between Main Group and f-Element Chemistry Transfer of ownership for 2010 Preface. Main Group Chemistry. 2009, 8 (4): 223-224.

Harvey MJ, Burkey DJ, Chmely SC, Hanusa TP. Stability of cyclopentadienyl aryloxide complexes of calcium and barium. Journal of Alloys and Compounds. 2009, 488 (2): 528-532.

Johns AM, Chmely SC, Hanusa TP. Solution Interaction of Potassium and Calcium Bis(trimethylsilyl)amides; Preparation of Ca[N(SiMe3)(2)](2) from Dibenzylcalcium. Inorganic Chemistry. 2009, 48 (4): 1380-1384.

Chmely SC, Carlson CN, Hanusa TP, Rheingold AL. Classical versus Bridged Allyl Ligands in Magnesium Complexes: The Role of Solvent. Journal of the American Chemical Society. 2009, 131 (18): 6344-+.

Meredith MB, Crisp JA, Brady ED, Hanusa TP, Yee GT, Pink M, Brennessel WW, Young VG. Tunable Spin-Crossover Behavior in Polymethylated Bis(indenyl)chromium(II) Complexes: The Significance of Benzo-Ring Substitution. Organometallics. 2008, 27 (21): 5464-5473.

Brady ED, ChmelySC, JayaratneKC, HanusaTP, Young VG, Jr. s-Block Metal Complexes of the Bis(tetramethylcyclopentadienyl) Phosphonium Diylide [Me(t-Bu)P(C5Me4)2] . Organometallics. 2008, 27 (7): 1612-1616.

Quisenberry KT, Gren CK, White RE, Hanusa TP, Brennessel WW. Trimethylsilylated allyl complexes of the heavy alkali metals, M[1,3-(SiMe3)(2)C3H3](thf)(n) (M = K, Cs). Organometallics. 2007, 26 (17): 4354-4356.

White RE, Hanusa TP, Kucera BE. Compositional variations in monomeric trimethylsilylated allyl lanthanide complexes. Journal of Organometallic Chemistry. 2007, 692 (16): 3479-3485.

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