William J. Evans (chemist)

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William J. Evans is a Distinguished Professor at the University of California, Irvine, who specializes in the inorganic and organometallic chemistry of heavy metals, specifically the rare earth metals (i.e. Sc, Y, and the lanthanides), actinides, and bismuth. He has published over 500 peer-reviewed research papers on these topics.

Evans was born in Madison, Wisconsin, and raised in Menomonee Falls, Wisconsin. He received a Bachelor of Science degree at the University of Wisconsin-Madison in 1969 where he did undergraduate research on pentaborane chemistry with Professor Donald F. Gaines. Subsequently, he attended the University of California, Los Angeles, where he obtained his PhD degree in 1973. His PhD research on the synthesis of metallocarboranes was supervised by Professor M. Frederick Hawthorne. He did postdoctoral research at Cornell University on the synthesis of transition metal phosphite complexes under the direction of Professor Earl L. Muetterties.

Evans began his independent research career in 1975 at the University of Chicago. He chose an area of research completely different from his training and experience, namely the chemistry of the rare-earth metals and actinides, with the central thesis that the special properties of these metals should lead to unique chemistry. He used exploratory synthesis to generate the new molecular species with the appropriate coordination environments to allow the special chemistry of these metals to be accessed. After receiving tenure at Chicago in 1982, he was recruited to the University of California, Irvine, where he has been a Professor since 1983. Among his recent accomplishments at UCI is the discovery of molecular species containing nine new rare earth and actinide oxidation states.

Evans is one of the few people to have received the American Chemical Society (ACS) Awards in both Inorganic Chemistry and Organometallic Chemistry. He has also received the Sir Edward Franklin Award and the Centenary Prize of the Royal Society of Chemistry, the Frank Spedding Award for Excellence in the Science and Technology of Rare Earths, the Terrae Rarae Award of the Tage der Seltenen Erden Society in Germany, the Richard C. Tolman Award of the Southern California Section of the ACS, [1] a Special Creativity Extension Award from the National Science Foundation, the UCI Distinguished Faculty Award for Research, and the UCI Physical Sciences Outstanding Contributions to Undergraduate Education Award. He was also honored with UCI's highest faculty award, the Lauds and Laurels Outstanding Faculty Achievement Award. Recently, he was named Director of the Eddleman Quantum Institute at UCI and has been active in promoting interdisciplinary quantum science.

Research

Evans initially examined metal vapor methods to make new classes of lanthanide complexes in the 0 oxidation state. [2] In efforts to characterize these products he identified the first crystallographically characterized lanthanide hydrides, [(C5H5)2(THF)Ln(µ-H)]2 (Ln = rare-earth metal), and the first soluble organometallic complex of samarium in the +2 oxidation state, (C5Me5)2Sm(THF)2. The latter complex demonstrated that lanthanide complexes could accomplish small molecule activation in unique ways, e.g. by reductive homologation of three CO molecules to (O2CC=C=O)2-. Desolvation of (C5Me5)2Sm(THF)2 formed the first bent metallocene with no other ligands, (C5Me5)2Sm. [3]

Decamethylsamarocene, as it was called, was surprising because it was previously thought that large cyclooctatetraenyl rings were required with lanthanides and actinides to form two ring metallocenes. (C5Me5)2Sm was even more unusual in that it had a bent geometry instead of the parallel plane ferrocene-like structure expected for a simple ionic complex of a +2 ion with two large anionic cyclopentadienyl rings.

(C5Me5)2Sm provided the first evidence of a rare-earth metal dinitrogen complex, [(C5Me5)2Sm]2(µ-η2:η2-N2). More importantly, this was the first example of a coplanar arrangement of dinitrogen with two metal atoms. Previous M2N2 complexes had a butterfly geometry in which each metal could interact with a perpendicular N−N pi bond.

Subsequent studies of lanthanide-based dinitrogen reduction led to over forty crystallographically characterized examples of the formerly unprecedented planar M2(µ-η2:η2-N2) structures. These studies also led to the first examples of complexes of (N2)3- and (NO)2- radical anions. In collaboration with Professor Jeffrey R. Long, the (N2)3- complexes were found to constitute a new class of single-molecule magnets.

Evans' synthetic study of (C5Me5)2Sm led to the discovery a series of sterically crowded tris(pentamethylcyclopentadienyl) (C5Me5)3M complexes (M = rare earth and actinide). Previously, it was thought that three of these large ligands could not fit around any metal. This discovery was significant because of the metal-ligand bond lengths in these complexes were 0.1 Å longer than conventional distances. The sterically crowded (C5Me5)3M complexes exhibit reduction chemistry termed sterically induced reduction (SIR), as well as η1-alkyl reactivity.

Further exploration of dinitrogen reduction led to the synthesis of the first crystallographically characterizable molecular complexes containing Pr2+, Gd2+, Tb2+, Ho2+, Y2+, Er2+, and Lu2+ ions. These new lanthanide ions unexpectedly had 4fn5d1 electron configurations, and not the conventional 4fn+1 configuration generated by reduction of 4fn Ln3+ ions of Eu, Yb, Sm, Tm Dy, and Nd. The first molecular complexes of U2+ and Th2+ were also discovered in the Evans lab. In the Th2+ case, the complex contained the first example of any ion with a 6d2 electron configuration. This is the configuration expected for superheavy metal ions like Rf2+ and Db3+. [4]

Related Research Articles

The lanthanide or lanthanoid series of chemical elements comprises the 14 metallic chemical elements with atomic numbers 57–70, from lanthanum through ytterbium. Lutetium is also sometimes considered a lanthanide, despite being a d-block element and a transition metal. These elements are often collectively known as the rare-earth elements or rare-earth metals.

<span class="mw-page-title-main">Europium(III) chloride</span> Chemical compound

Europium(III) chloride is an inorganic compound with the formula EuCl3. The anhydrous compound is a yellow solid. Being hygroscopic it rapidly absorbs water to form a white crystalline hexahydrate, EuCl3·6H2O, which is colourless. The compound is used in research.

<span class="mw-page-title-main">Hapticity</span> Number of contiguous atoms in a ligand that bond to the central atom in a coordination complex

In coordination chemistry, hapticity is the coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms. The hapticity of a ligand is described with the Greek letter η ('eta'). For example, η2 describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated. In addition, if the ligand coordinates through multiple atoms that are not contiguous then this is considered denticity, and the κ-notation is used once again. When naming complexes care should be taken not to confuse η with μ ('mu'), which relates to bridging ligands.

Transmetalation (alt. spelling: transmetallation) is a type of organometallic reaction that involves the transfer of ligands from one metal to another. It has the general form:

<span class="mw-page-title-main">Sandwich compound</span> Chemical compound made of two ring ligands bound to a metal

In organometallic chemistry, a sandwich compound is a chemical compound featuring a metal bound by haptic, covalent bonds to two arene (ring) ligands. The arenes have the formula CnHn, substituted derivatives and heterocyclic derivatives. Because the metal is usually situated between the two rings, it is said to be "sandwiched". A special class of sandwich complexes are the metallocenes.

<span class="mw-page-title-main">Organoactinide chemistry</span> Study of chemical compounds containing actinide-carbon bonds

Organoactinide chemistry is the science exploring the properties, structure, and reactivity of organoactinide compounds, which are organometallic compounds containing a carbon to actinide chemical bond.

<span class="mw-page-title-main">Transition metal dinitrogen complex</span> Coordination compounds with N2

Transition metal dinitrogen complexes are coordination compounds that contain transition metals as ion centers the dinitrogen molecules (N2) as ligands.

In chemistry, a sterically induced reduction happens when an oxidized metal behaves as, and exhibits similar reducing properties to, the more reduced form of the metal. This effect is mainly caused by the surrounding ligands that are complexed to the metal and it is the ligands that are involved in the reduction chemistry instead of the metal due to electronic destabilization by being significantly distanced from the metal. Sterically induced reductions commonly involve metals found in the lanthanoid and actinoid series.

<span class="mw-page-title-main">Organoscandium chemistry</span> Chemistry of compounds containing a carbon to scandium chemical bond

Organoscandium chemistry is an area with organometallic compounds focused on compounds with at least one carbon to scandium chemical bond. The interest in organoscandium compounds is mostly academic but motivated by potential practical applications in catalysis, especially in polymerization. A common precursor is scandium chloride, especially its THF complex.

<span class="mw-page-title-main">Rhodocene</span> Organometallic chemical compound

Rhodocene is a chemical compound with the formula [Rh(C5H5)2]. Each molecule contains an atom of rhodium bound between two planar aromatic systems of five carbon atoms known as cyclopentadienyl rings in a sandwich arrangement. It is an organometallic compound as it has (haptic) covalent rhodium–carbon bonds. The [Rh(C5H5)2] radical is found above 150 °C (302 °F) or when trapped by cooling to liquid nitrogen temperatures (−196 °C [−321 °F]). At room temperature, pairs of these radicals join via their cyclopentadienyl rings to form a dimer, a yellow solid.

<span class="mw-page-title-main">Metal bis(trimethylsilyl)amides</span>

Metal bis(trimethylsilyl)amides are coordination complexes composed of a cationic metal M with anionic bis(trimethylsilyl)amide ligands (the −N 2 monovalent anion, or −N 2 monovalent group, and are part of a broader category of metal amides.

<span class="mw-page-title-main">Cyclopentadienyliron dicarbonyl dimer</span> Chemical compound

Cyclopentadienyliron dicarbonyl dimer is an organometallic compound with the formula [(η5-C5H5)Fe(CO)2]2, often abbreviated to Cp2Fe2(CO)4, [CpFe(CO)2]2 or even Fp2, with the colloquial name "fip dimer". It is a dark reddish-purple crystalline solid, which is readily soluble in moderately polar organic solvents such as chloroform and pyridine, but less soluble in carbon tetrachloride and carbon disulfide. Cp2Fe2(CO)4 is insoluble in but stable toward water. Cp2Fe2(CO)4 is reasonably stable to storage under air and serves as a convenient starting material for accessing other Fp (CpFe(CO)2) derivatives (described below).

<span class="mw-page-title-main">Bis(dinitrogen)bis(1,2-bis(diphenylphosphino)ethane)molybdenum(0)</span> Chemical compound

trans-Bis(dinitrogen)bis[1,2-bis(diphenylphosphino)ethane]molybdenum(0) is a coordination complex with the formula Mo(N2)2(dppe)2. It is a relatively air stable yellow-orange solid. It is notable as being the first discovered dinitrogen containing complex of molybdenum.

<span class="mw-page-title-main">Actinocene</span> Class of chemical compounds

Actinocenes are a family of organoactinide compounds consisting of metallocenes containing elements from the actinide series. They typically have a sandwich structure with two dianionic cyclooctatetraenyl ligands (COT2-, which is C
8H2−
8) bound to an actinide-metal center (An) in the oxidation state IV, resulting in the general formula An(C8H8)2.

In organometallic chemistry, f-block metallocenes are a class of sandwich compounds consisting of an f-block metal and a set of electron-rich ligands such as the cyclopentadienyl anion.

<span class="mw-page-title-main">Jaqueline Kiplinger</span> American inorganic chemist

Jaqueline Kiplinger is an American inorganic chemist who specializes in organometallic actinide chemistry. Over the course of her career, she has done extensive work with fluorocarbons and actinides. She is currently a Fellow of the Materials Synthesis and Integrated Devices group in the Materials Physics and Applications Division of Los Alamos National Laboratory (LANL). Her current research interests are focused on the development of chemistry for the United States’ national defense and energy needs.

Russell P. Hughes an American/British chemist, is the Frank R. Mori Professor Emeritus and Research Professor in the Department of Chemistry at Dartmouth College. His research interests are in organometallic chemistry, with emphasis on the chemistry of transition metal complexes interacting with fluorocarbons. His research group’s work in this area led to several creative syntheses of complexes of transition metal and perfluorinated hydrocarbon fragments.

<span class="mw-page-title-main">Lanthanocene</span>

A lanthanocene is a type of metallocene compound that contains an element from the lanthanide series. The most common lanthanocene complexes contain two cyclopentadienyl anions and an X type ligand, usually hydride or alkyl ligand.

Karsten Meyer is a German inorganic chemist and Chair of Inorganic and General Chemistry at the Friedrich-Alexander University of Erlangen-Nürnberg (FAU). His research involves the coordination chemistry of transition metals as well as uranium coordination chemistry, small molecule activation with these coordination complexes, and the synthesis of new chelating ligands. He is the 2017 recipient of the Elhuyar-Goldschmidt Award of the Spanish Royal Society of Chemistry, the Ludwig-Mond Award of the Royal Society of Chemistry, and the L.A. Chugaev Commemorative Medal of the Russian Academy of Sciences, among other awards. He also serves as an Associate Editor of the journal Organometallics since 2014.

Lutetium compounds are compounds formed by the lanthanide metal lutetium (Lu). In these compounds, lutetium generally exhibits the +3 oxidation state, such as LuCl3, Lu2O3 and Lu2(SO4)3. Aqueous solutions of most lutetium salts are colorless and form white crystalline solids upon drying, with the common exception of the iodide. The soluble salts, such as nitrate, sulfate and acetate form hydrates upon crystallization. The oxide, hydroxide, fluoride, carbonate, phosphate and oxalate are insoluble in water.

References

  1. ↑ "2014 William J. Evans, UC Irvine – SCALACS". SCALACS – Southern California Section of the American Chemical Society. June 11, 2015. Retrieved November 19, 2023.
  2. ↑ Evans, William J. (2018). "Biosketch for Professor William J. Evans". Journal of Organometallic Chemistry. 857: 2–4. doi:10.1016/j.jorganchem.2018.01.043.
  3. ↑ Evans, William J. (2007). "The Importance of Questioning Scientific Assumptions: Some Lessons from f Element Chemistry†". Inorganic Chemistry. 46 (9): 3435–3449. doi:10.1021/ic062011k. PMID   17428046.
  4. ↑ Evans, William J. (2016). "Tutorial on the Role of Cyclopentadienyl Ligands in the Discovery of Molecular Complexes of the Rare-Earth and Actinide Metals in New Oxidation States". Organometallics. 35 (18): 3088–3100. doi: 10.1021/acs.organomet.6b00466 .
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