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Glotz G, Püschmann S, Haas M, Gescheidt G. Direct detection of photo-induced reactions by IR: from Brook rearrangement to photo-catalysis. Photochem Photobiol Sci 2023:10.1007/s43630-023-00406-4. [PMID: 36933157 DOI: 10.1007/s43630-023-00406-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 02/28/2023] [Indexed: 03/19/2023]
Abstract
In situ IR detection of photoreactions induced by the light of LEDs at appropriate wavelengths provides a simple, cost-effective, and versatile method to get insight into mechanistic details. In particular, conversions of functional groups can be selectively followed. Overlapping UV-Vis bands or fluorescence from the reactants and products and the incident light do not obstruct IR detection. Compared with in situ photo-NMR, our setup does not require tedious sample preparation (optical fibers) and offers a selective detection of reactions, even at positions where 1H-NMR lines overlap or 1H resonances are not clear-cut. We illustrate the applicability of our setup following the photo-Brook rearrangement of (adamant-1-yl-carbonyl)-tris(trimethylsilyl)silane, address photo-induced α-bond cleavage (1-hydroxycyclohexyl phenyl ketone), study photoreduction using tris(bipyridine)ruthenium(II), investigate photo-oxygenation of double bonds with molecular oxygen and the fluorescent 2,4,6-triphenylpyrylium photocatalyst, and address photo-polymerization. With the LED/FT-IR combination, reactions can be qualitatively followed in fluid solution, (highly) viscous environments, and in the solid state. Viscosity changes during the reaction (e.g., during a polymerization) do not obstruct the method.
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Affiliation(s)
- Gabriel Glotz
- Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremayrgasse 9/II, 8010, Graz, Austria.
| | - Sabrina Püschmann
- Institute of Inorganic Chemistry, Graz University of Technology, Stremayrgasse 9/IV, 8010, Graz, Austria
| | - Michael Haas
- Institute of Inorganic Chemistry, Graz University of Technology, Stremayrgasse 9/IV, 8010, Graz, Austria
| | - Georg Gescheidt
- Institute of Physical and Theoretical Chemistry, Graz University of Technology, Stremayrgasse 9/II, 8010, Graz, Austria
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2
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Tripodi G, Roithová J. Unmasking the Iron-Oxo Bond of the [(Ligand)Fe-OIAr] 2+/+ Complexes. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:1636-1643. [PMID: 35920859 PMCID: PMC9460779 DOI: 10.1021/jasms.2c00094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 07/26/2022] [Accepted: 07/26/2022] [Indexed: 06/15/2023]
Abstract
ArIO (ArI = 2-(tBuSO2)C6H4I) is an oxidant used to oxidize FeII species to their FeIV-oxo state, enabling hydrogen-atom transfer (HAT) and oxygen-atom transfer (OAT) reactions at low energy barriers. ArIO, as a ligand, generates masked Fen═O species of the type Fe(n-2)-OIAr. Herein, we used gas-phase ion-molecule reactions and DFT calculations to explore the properties of masked iron-oxo species and to understand their unmasking mechanisms. The theory shows that the I-O bond cleavage in [(TPA)FeIVO(ArIO)]2+ (12+, TPA = tris(2-pyridylmethyl)amine)) is highly endothermic; therefore, it can be achieved only in collision-induced dissociation of 12+ leading to the unmasked iron(VI) dioxo complex. The reduction of 12+ by HAT leads to [(TPA)FeIIIOH(ArIO)]2+ with a reduced energy demand for the I-O bond cleavage but is, however, still endothermic. The exothermic unmasking of the Fe═O bond is predicted after one-electron reduction of 12+ or after OAT reactivity. The latter leads to the 4e- oxidation of unsaturated hydrocarbons: The initial OAT from [(TPA)FeIVO(ArIO)]2+ leads to the epoxidation of an alkene and triggers the unmasking of the second Fe═O bond still within one collisional complex. The second oxidation step starts with HAT from a C-H bond and follows with the rebound of the C-radical and the OH group. The process starting with the one-electron reduction could be studied with [(TQA)FeIVO(ArIO)]2+ (22+, TQA = tris(2-quinolylmethyl)amine)) because it has a sufficient electron affinity for electron transfer with alkenes. Accordingly, the reaction of 22+ with 2-carene leads to [(TQA)FeIIIO(ArIO)]2+ that exothermically eliminates ArI and unmasks the reactive FeV-dioxo species.
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3
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Takebayashi S, Fayzullin RR, Bansal R. Direct observation of reversible bond homolysis by 2D EXSY NMR. Chem Sci 2022; 13:9202-9209. [PMID: 36093009 PMCID: PMC9383717 DOI: 10.1039/d2sc03028d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 07/07/2022] [Indexed: 11/21/2022] Open
Abstract
Bond homolysis is one of the most fundamental bond cleavage mechanisms. Thus, understanding of bond homolysis influences the development of a wide range of chemistry. Photolytic bond homolysis and its reverse process have been observed directly using time-resolved spectroscopy. However, direct observation of reversible bond homolysis remains elusive. Here, we report the direct observation of reversible Co–Co bond homolysis using two-dimensional nuclear magnetic resonance exchange spectroscopy (2D EXSY NMR). The characterization of species involved in this homolysis is firmly supported by diffusion ordered NMR spectroscopy (DOSY NMR). The unambiguous characterization of the Co–Co bond homolysis process enabled us to study ligand steric and electronic factors that influence the strength of the Co–Co bond. Understanding of these factors will contribute to rational design of multimetallic complexes with desired physical properties or catalytic activity. We report the first direct observation of reversible bond homolysis using EXSY NMR. This study revealed that electron donating groups weaken the Co–Co bond.![]()
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Affiliation(s)
- Satoshi Takebayashi
- Science and Technology Group Okinawa Institute of Science and Technology Graduate University 1919-1 Tancha, Onna-son, Okinawa 904-0495, Japan
| | - Robert R. Fayzullin
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center, Russian Academy of Sciences, 8 Arbuzov Street, Kazan 420088, Russian Federation
| | - Richa Bansal
- Science and Technology Group Okinawa Institute of Science and Technology Graduate University 1919-1 Tancha, Onna-son, Okinawa 904-0495, Japan
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4
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Bullock RM, Chen JG, Gagliardi L, Chirik PJ, Farha OK, Hendon CH, Jones CW, Keith JA, Klosin J, Minteer SD, Morris RH, Radosevich AT, Rauchfuss TB, Strotman NA, Vojvodic A, Ward TR, Yang JY, Surendranath Y. Using nature's blueprint to expand catalysis with Earth-abundant metals. Science 2020; 369:eabc3183. [PMID: 32792370 PMCID: PMC7875315 DOI: 10.1126/science.abc3183] [Citation(s) in RCA: 204] [Impact Index Per Article: 51.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Numerous redox transformations that are essential to life are catalyzed by metalloenzymes that feature Earth-abundant metals. In contrast, platinum-group metals have been the cornerstone of many industrial catalytic reactions for decades, providing high activity, thermal stability, and tolerance to chemical poisons. We assert that nature's blueprint provides the fundamental principles for vastly expanding the use of abundant metals in catalysis. We highlight the key physical properties of abundant metals that distinguish them from precious metals, and we look to nature to understand how the inherent attributes of abundant metals can be embraced to produce highly efficient catalysts for reactions crucial to the sustainable production and transformation of fuels and chemicals.
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Affiliation(s)
- R Morris Bullock
- Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
| | - Jingguang G Chen
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA.
- Chemistry Division, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Laura Gagliardi
- Department of Chemistry, Minnesota Supercomputing Institute, and Chemical Theory Center, University of Minnesota, Minneapolis, MN 55455, USA.
| | - Paul J Chirik
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Omar K Farha
- Department of Chemistry and Chemical and Biological Engineering, Northwestern University, Evanston, IL 60208, USA
| | - Christopher H Hendon
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA
| | - Christopher W Jones
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - John A Keith
- Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Jerzy Klosin
- Core R&D, Dow Chemical Co., Midland, MI 48674, USA
| | - Shelley D Minteer
- Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA
| | - Robert H Morris
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Alexander T Radosevich
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Thomas B Rauchfuss
- School of Chemical Sciences, University of Illinois, Urbana, IL 61801, USA
| | - Neil A Strotman
- Process Research and Development, Merck & Co. Inc., Rahway, NJ 07065, USA
| | - Aleksandra Vojvodic
- Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Thomas R Ward
- Department of Chemistry, University of Basel, CH-4058 Basel, Switzerland
| | - Jenny Y Yang
- Department of Chemistry, University of California, Irvine, CA 92697, USA
| | - Yogesh Surendranath
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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5
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Chambers GM, Wiedner ES, Bullock RM. H
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Oxidation Electrocatalysis Enabled by Metal‐to‐Metal Hydrogen Atom Transfer: A Homolytic Approach to a Heterolytic Reaction. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201807510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Geoffrey M. Chambers
- Center for Molecular Electrocatalysis Pacific Northwest National Laboratory Richland WA 99352 USA
| | - Eric S. Wiedner
- Center for Molecular Electrocatalysis Pacific Northwest National Laboratory Richland WA 99352 USA
| | - R. Morris Bullock
- Center for Molecular Electrocatalysis Pacific Northwest National Laboratory Richland WA 99352 USA
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6
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Chambers GM, Wiedner ES, Bullock RM. H
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Oxidation Electrocatalysis Enabled by Metal‐to‐Metal Hydrogen Atom Transfer: A Homolytic Approach to a Heterolytic Reaction. Angew Chem Int Ed Engl 2018; 57:13523-13527. [DOI: 10.1002/anie.201807510] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Indexed: 02/03/2023]
Affiliation(s)
- Geoffrey M. Chambers
- Center for Molecular Electrocatalysis Pacific Northwest National Laboratory Richland WA 99352 USA
| | - Eric S. Wiedner
- Center for Molecular Electrocatalysis Pacific Northwest National Laboratory Richland WA 99352 USA
| | - R. Morris Bullock
- Center for Molecular Electrocatalysis Pacific Northwest National Laboratory Richland WA 99352 USA
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7
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8
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Lee R, Tan D, Liu C, Li H, Guo H, Shyue JJ, Huang KW. DFT mechanistic study of the selective terminal C–H activation of n -pentane with a tungsten allyl nitrosyl complex. JOURNAL OF SAUDI CHEMICAL SOCIETY 2017. [DOI: 10.1016/j.jscs.2016.12.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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9
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Abstract
Transition metal hydride complexes are usually amphoteric, not only acting as hydride donors, but also as Brønsted-Lowry acids. A simple additive ligand acidity constant equation (LAC for short) allows the estimation of the acid dissociation constant Ka(LAC) of diamagnetic transition metal hydride and dihydrogen complexes. It is remarkably successful in systematizing diverse reports of over 450 reactions of acids with metal complexes and bases with metal hydrides and dihydrogen complexes, including catalytic cycles where these reactions are proposed or observed. There are links between pKa(LAC) and pKa(THF), pKa(DCM), pKa(MeCN) for neutral and cationic acids. For the groups from chromium to nickel, tables are provided that order the acidity of metal hydride and dihydrogen complexes from most acidic (pKa(LAC) -18) to least acidic (pKa(LAC) 50). Figures are constructed showing metal acids above the solvent pKa scales and organic acids below to summarize a large amount of information. Acid-base features are analyzed for catalysts from chromium to gold for ionic hydrogenations, bifunctional catalysts for hydrogen oxidation and evolution electrocatalysis, H/D exchange, olefin hydrogenation and isomerization, hydrogenation of ketones, aldehydes, imines, and carbon dioxide, hydrogenases and their model complexes, and palladium catalysts with hydride intermediates.
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Affiliation(s)
- Robert H Morris
- Department of Chemistry, University of Toronto , 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada
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10
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Yang Y, Liu L, Chen J, Han K. Hydrogen bonding tunes the early stage of hydrogen-atom abstracting reaction. Phys Chem Chem Phys 2014; 16:17828-34. [PMID: 25036436 DOI: 10.1039/c4cp01371a] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The spontaneous and collision-assisted hydrogen-atom abstracting reaction (HA) dynamics of triplet benzil are investigated through the combination of transient absorption spectroscopy with TD-DFT calculations. HA dynamics exhibit a remarkable dependence on the hydrogen donor properties. The effects of the triplet-state hydrogen bonding on the reaction dynamics are illustrated. In particular, it is experimentally observed that strengthened triplet-state hydrogen bonding could accelerate the HA, whereas weakened triplet-state hydrogen bonding would postpone the HA. The triplet-state hydrogen bonding has great influences on the early stage of the HA reaction, while the bond dissociation energy of the hydrogen donors determines the subsequent reaction pathways. Protic solvents could sustain longer lifetimes of the excited-state intermediate formed after HA than non-protic solvents by 10 μs. This investigation provides insights into the HA dynamics and guidance to improve the product efficiency of photochemical reactions.
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Affiliation(s)
- Yang Yang
- State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
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11
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Laws DR, Bullock RM, Lee R, Huang KW, Geiger WE. Comparison of the One-Electron Oxidations of CO-Bridged vs Unbridged Bimetallic Complexes: Electron-Transfer Chemistry of Os2Cp2(CO)4 and Os2Cp*2(μ-CO)2(CO)2 (Cp = η5-C5H5, Cp* = η5-C5Me5). Organometallics 2014. [DOI: 10.1021/om401213y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Derek R. Laws
- Department
of Chemistry, University of Vermont, Burlington, Vermont 05405 United States
| | - R. Morris Bullock
- Physical
Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, Washington 99352 United States
| | - Richmond Lee
- KAUST
Catalysis Center and Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Kuo-Wei Huang
- KAUST
Catalysis Center and Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - William E. Geiger
- Department
of Chemistry, University of Vermont, Burlington, Vermont 05405 United States
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12
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Lewandowska-Andralojc A, Grills DC, Zhang J, Bullock RM, Miyazawa A, Kawanishi Y, Fujita E. Kinetic and Mechanistic Studies of Carbon-to-Metal Hydrogen Atom Transfer Involving Os-Centered Radicals: Evidence for Tunneling. J Am Chem Soc 2014; 136:3572-8. [DOI: 10.1021/ja4123076] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - David C. Grills
- Chemistry
Department, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
| | - Jie Zhang
- Chemistry
Department, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
| | - R. Morris Bullock
- Physical
Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, K2-57, Richland, Washington 99352, United States
| | - Akira Miyazawa
- National Institute of Advanced Industrial Science and Technology, 4-2-1 Nigatake,
Miyagino, Sendai, Miyagi 983-8551, Japan
| | - Yuji Kawanishi
- National Institute of Advanced Industrial Science and Technology, Tsukuba Central 5, 1-1-1, Higashi, Tsukuba, Ibaraki, 305-8565, Japan
| | - Etsuko Fujita
- Chemistry
Department, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
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13
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van der Eide EF, Helm ML, Walter ED, Bullock RM. Structural and spectroscopic characterization of 17- and 18-electron piano-stool complexes of chromium. Thermochemical analyses of weak Cr-H bonds. Inorg Chem 2013; 52:1591-603. [PMID: 23343354 DOI: 10.1021/ic302460y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The 17-electron radical CpCr(CO)(2)(IMe)(•) (IMe = 1,3-dimethylimidazol-2-ylidene) was synthesized by the reaction of IMe with [CpCr(CO)(3)](2), and characterized by single crystal X-ray diffraction and by electron paramagnetic resonance (EPR), IR, and variable temperature (1)H NMR spectroscopy. The metal-centered radical is monomeric under all conditions and exhibits Curie paramagnetic behavior in solution. An electrochemically reversible reduction to 18-electron CpCr(CO)(2)(IMe)(-) takes place at E(1/2) = -1.89(1) V vs Cp(2)Fe(+•/0) in MeCN, and was accomplished chemically with KC(8) in tetrahydrofuran (THF). The salts K(+)(18-crown-6)[CpCr(CO)(2)(IMe)](-)·½THF and K(+)[CpCr(CO)(2)(IMe)](-)·(3)/(4)THF were crystallographically characterized. Monomeric ion pairs are found in the former, whereas the latter has a polymeric structure because of a network of K···O((CO)) interactions. Protonation of K(+)(18-crown-6)[CpCr(CO)(2)(IMe)](-)·½THF gives the hydride CpCr(CO)(2)(IMe)H, which could not be isolated, but was characterized in solution; a pK(a) of 27.2(4) was determined in MeCN. A thermochemical analysis provides the Cr-H bond dissociation free energy (BDFE) for CpCr(CO)(2)(IMe)H in MeCN solution as 47.3(6) kcal mol(-1). This value is exceptionally low for a transition metal hydride, and implies that the reaction 2 [Cr-H] → 2 [Cr(•)] + H(2) is exergonic (ΔG = -9.0(8) kcal mol(-1)). This analysis explains the experimental observation that generated solutions of the hydride produce CpCr(CO)(2)(IMe)(•) (typically on the time scale of days). By contrast, CpCr(CO)(2)(PCy(3))H has a higher Cr-H BDFE (52.9(4) kcal mol(-1)), is more stable with respect to H(2) loss, and is isolable.
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Affiliation(s)
- Edwin F van der Eide
- Chemical and Materials Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, USA
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14
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Proton–coupled electron transfer versus hydrogen atom transfer: A density functional reactivity theory characterization. COMPUT THEOR CHEM 2012. [DOI: 10.1016/j.comptc.2012.02.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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15
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Fu Y, Romero MJ, Habtemariam A, Snowden ME, Song L, Clarkson GJ, Qamar B, Pizarro AM, Unwin PR, Sadler PJ. The contrasting chemical reactivity of potent isoelectronic iminopyridine and azopyridine osmium(ii) arene anticancer complexes. Chem Sci 2012. [DOI: 10.1039/c2sc20220d] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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16
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Estes DP, Vannucci AK, Hall AR, Lichtenberger DL, Norton JR. Thermodynamics of the Metal–Hydrogen Bonds in (η5-C5H5)M(CO)2H (M = Fe, Ru, Os). Organometallics 2011. [DOI: 10.1021/om2001519] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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17
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Liu S, Ess DH, Schauer CK. Density Functional Reactivity Theory Characterizes Charge Separation Propensity in Proton-Coupled Electron Transfer Reactions. J Phys Chem A 2011; 115:4738-42. [DOI: 10.1021/jp112319d] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shubin Liu
- Research Computing Center, University of North Carolina, Chapel Hill, North Carolina 27599-3420, United States
| | - Daniel H. Ess
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, United States
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
| | - Cynthia K. Schauer
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
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18
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Mader EA, Manner VW, Markle TF, Wu A, Franz JA, Mayer JM. Trends in ground-state entropies for transition metal based hydrogen atom transfer reactions. J Am Chem Soc 2009; 131:4335-45. [PMID: 19275235 PMCID: PMC2723939 DOI: 10.1021/ja8081846] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reported herein are thermochemical studies of hydrogen atom transfer (HAT) reactions involving transition metal H-atom donors M(II)LH and oxyl radicals. [Fe(II)(H(2)bip)(3)](2+), [Fe(II)(H(2)bim)(3)](2+), [Co(II)(H(2)bim)(3)](2+), and Ru(II)(acac)(2)(py-imH) [H(2)bip = 2,2'-bi-1,4,5,6-tetrahydropyrimidine, H(2)bim = 2,2'-bi-imidazoline, acac = 2,4-pentandionato, py-imH = 2-(2'-pyridyl)imidazole)] each react with TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) or (t)Bu(3)PhO(*) (2,4,6-tri-tert-butylphenoxyl) to give the deprotonated, oxidized metal complex M(III)L and TEMPOH or (t)Bu(3)PhOH. Solution equilibrium measurements for the reaction of [Co(II)(H(2)bim)(3)](2+) with TEMPO show a large, negative ground-state entropy for hydrogen atom transfer, -41 +/- 2 cal mol(-1) K(-1). This is even more negative than the DeltaS(o)(HAT) = -30 +/- 2 cal mol(-1) K(-1) for the two iron complexes and the DeltaS(o)(HAT) for Ru(II)(acac)(2)(py-imH) + TEMPO, 4.9 +/- 1.1 cal mol(-1) K(-1), as reported earlier. Calorimetric measurements quantitatively confirm the enthalpy of reaction for [Fe(II)(H(2)bip)(3)](2+) + TEMPO, thus also confirming DeltaS(o)(HAT). Calorimetry on TEMPOH + (t)Bu(3)PhO(*) gives DeltaH(o)(HAT) = -11.2 +/- 0.5 kcal mol(-1) which matches the enthalpy predicted from the difference in literature solution BDEs. A brief evaluation of the literature thermochemistry of TEMPOH and (t)Bu(3)PhOH supports the common assumption that DeltaS(o)(HAT) approximately 0 for HAT reactions of organic and small gas-phase molecules. However, this assumption does not hold for transition metal based HAT reactions. The trend in magnitude of |DeltaS(o)(HAT)| for reactions with TEMPO, Ru(II)(acac)(2)(py-imH) << [Fe(II)(H(2)bip)(3)](2+) = [Fe(II)(H(2)bim)(3)](2+) < [Co(II)(H(2)bim)(3)](2+), is surprisingly well predicted by the trends for electron transfer half-reaction entropies, DeltaS(o)(ET), in aprotic solvents. This is because both DeltaS(o)(ET) and DeltaS(o)(HAT) have substantial contributions from vibrational entropy, which varies significantly with the metal center involved. The close connection between DeltaS(o)(HAT) and DeltaS(o)(ET) provides an important link between these two fields and provides a starting point from which to predict which HAT systems will have important ground-state entropy effects.
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Affiliation(s)
- Elizabeth A Mader
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195-1700, USA
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19
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Cho HG, Andrews L. Formation of carbyne complexes in reactions of laser-ablated Os atoms with halomethanes: characterization by C–H(X) and Os–H(X) stretching absorptions and computed structures. Dalton Trans 2009:5858-66. [PMID: 19623385 DOI: 10.1039/b811805a] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Han-Gook Cho
- Department of Chemistry, University of Incheon, 177 Dohwa-dong, Nam-ku, Incheon, 402-749, South Korea
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20
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Badger RC, D’Acchioli JS, Gamoke BC, Kim SB, Oudenhoven TA, Sweigart DA, Tanke RS. Chemical, Electrochemical, and Theoretical Investigations of [(Cp)Ru(CO)3]+ and [(Ind)Ru(CO)3]+. Organometallics 2008. [DOI: 10.1021/om800767g] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Robert C. Badger
- Department of Chemistry, The University of Wisconsin−Stevens Point, 2001 Fourth Avenue, Stevens Point, Wisconsin 54481, and Department of Chemistry, Brown University, Box H, 324 Brook Street, Providence, Rhode Island 02912
| | - Jason S. D’Acchioli
- Department of Chemistry, The University of Wisconsin−Stevens Point, 2001 Fourth Avenue, Stevens Point, Wisconsin 54481, and Department of Chemistry, Brown University, Box H, 324 Brook Street, Providence, Rhode Island 02912
| | - Benjamin C. Gamoke
- Department of Chemistry, The University of Wisconsin−Stevens Point, 2001 Fourth Avenue, Stevens Point, Wisconsin 54481, and Department of Chemistry, Brown University, Box H, 324 Brook Street, Providence, Rhode Island 02912
| | - Sang Bok Kim
- Department of Chemistry, The University of Wisconsin−Stevens Point, 2001 Fourth Avenue, Stevens Point, Wisconsin 54481, and Department of Chemistry, Brown University, Box H, 324 Brook Street, Providence, Rhode Island 02912
| | - Tracey A. Oudenhoven
- Department of Chemistry, The University of Wisconsin−Stevens Point, 2001 Fourth Avenue, Stevens Point, Wisconsin 54481, and Department of Chemistry, Brown University, Box H, 324 Brook Street, Providence, Rhode Island 02912
| | - Dwight A. Sweigart
- Department of Chemistry, The University of Wisconsin−Stevens Point, 2001 Fourth Avenue, Stevens Point, Wisconsin 54481, and Department of Chemistry, Brown University, Box H, 324 Brook Street, Providence, Rhode Island 02912
| | - Robin S. Tanke
- Department of Chemistry, The University of Wisconsin−Stevens Point, 2001 Fourth Avenue, Stevens Point, Wisconsin 54481, and Department of Chemistry, Brown University, Box H, 324 Brook Street, Providence, Rhode Island 02912
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Hartung J, Pulling ME, Smith DM, Yang DX, Norton JR. Initiating radical cyclizations by H transfer from transition metals. Tetrahedron 2008. [DOI: 10.1016/j.tet.2008.10.030] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Wu A, Mayer JM. Hydrogen atom transfer reactions of a ruthenium imidazole complex: hydrogen tunneling and the applicability of the Marcus cross relation. J Am Chem Soc 2008; 130:14745-54. [PMID: 18841973 PMCID: PMC2633126 DOI: 10.1021/ja805067h] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reaction of Ru(II)(acac)2(py-imH) (Ru(II)imH) with TEMPO(*) (2,2,6,6-tetramethylpiperidine-1-oxyl radical) in MeCN quantitatively gives Ru(III)(acac)2(py-im) (Ru(III)im) and the hydroxylamine TEMPO-H by transfer of H(*) (H(+) + e(-)) (acac = 2,4-pentanedionato, py-imH = 2-(2'-pyridyl)imidazole). Kinetic measurements of this reaction by UV-vis stopped-flow techniques indicate a bimolecular rate constant k(3H) = 1400 +/- 100 M(-1) s(-1) at 298 K. The reaction proceeds via a concerted hydrogen atom transfer (HAT) mechanism, as shown by ruling out the stepwise pathways of initial proton or electron transfer due to their very unfavorable thermochemistry (Delta G(o)). Deuterium transfer from Ru(II)(acac)2(py-imD) (Ru(II)imD) to TEMPO(*) is surprisingly much slower at k(3D) = 60 +/- 7 M(-1) s(-1), with k(3H)/k(3D) = 23 +/- 3 at 298 K. Temperature-dependent measurements of this deuterium kinetic isotope effect (KIE) show a large difference between the apparent activation energies, E(a3D) - E(a3H) = 1.9 +/- 0.8 kcal mol(-1). The large k(3H)/k(3D) and DeltaE(a) values appear to be greater than the semiclassical limits and thus suggest a tunneling mechanism. The self-exchange HAT reaction between Ru(II)imH and Ru(III)im, measured by (1)H NMR line broadening, occurs with k(4H) = (3.2 +/- 0.3) x 10(5) M(-1) s(-1) at 298 K and k(4H)/k(4D) = 1.5 +/- 0.2. Despite the small KIE, tunneling is suggested by the ratio of Arrhenius pre-exponential factors, log(A(4H)/A(4D)) = -0.5 +/- 0.3. These data provide a test of the applicability of the Marcus cross relation for H and D transfers, over a range of temperatures, for a reaction that involves substantial tunneling. The cross relation calculates rate constants for Ru(II)imH(D) + TEMPO(*) that are greater than those observed: k(3H,calc)/k(3H) = 31 +/- 4 and k(3D,calc)/k(3D) = 140 +/- 20 at 298 K. In these rate constants and in the activation parameters, there is a better agreement with the Marcus cross relation for H than for D transfer, despite the greater prevalence of tunneling for H. The cross relation does not explicitly include tunneling, so close agreement should not be expected. In light of these results, the strengths and weaknesses of applying the cross relation to HAT reactions are discussed.
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Affiliation(s)
- Adam Wu
- Department of Chemistry, University of Washington, Campus Box 351700, Seattle, WA, 98195-1700, USA
| | - James M. Mayer
- Department of Chemistry, University of Washington, Campus Box 351700, Seattle, WA, 98195-1700, USA
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Xu B, Li QS, Xie Y, King RB, Schaefer HF. Unsaturated Binuclear Cyclopentadienylosmium Carbonyl Derivatives: Comparison with Their Iron Analogues. Organometallics 2008. [DOI: 10.1021/om800649r] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Bing Xu
- Institute of Chemical Physics, Beijing Institute of Technology, Beijing 100081, Peopleʼs Republic of China, Center for Computational Quantum Chemistry, School of Chemistry and Environment, South China Normal University, Guangzhou 510631, Peopleʼs Republic of China, and Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602
| | - Qian-Shu Li
- Institute of Chemical Physics, Beijing Institute of Technology, Beijing 100081, Peopleʼs Republic of China, Center for Computational Quantum Chemistry, School of Chemistry and Environment, South China Normal University, Guangzhou 510631, Peopleʼs Republic of China, and Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602
| | - Yaoming Xie
- Institute of Chemical Physics, Beijing Institute of Technology, Beijing 100081, Peopleʼs Republic of China, Center for Computational Quantum Chemistry, School of Chemistry and Environment, South China Normal University, Guangzhou 510631, Peopleʼs Republic of China, and Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602
| | - R. Bruce King
- Institute of Chemical Physics, Beijing Institute of Technology, Beijing 100081, Peopleʼs Republic of China, Center for Computational Quantum Chemistry, School of Chemistry and Environment, South China Normal University, Guangzhou 510631, Peopleʼs Republic of China, and Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602
| | - Henry F. Schaefer
- Institute of Chemical Physics, Beijing Institute of Technology, Beijing 100081, Peopleʼs Republic of China, Center for Computational Quantum Chemistry, School of Chemistry and Environment, South China Normal University, Guangzhou 510631, Peopleʼs Republic of China, and Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602
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Becker E, Pavlik S, Kirchner K. The Organometallic Chemistry of Group 8 Tris(pyrazolyl)borate Complexes. ADVANCES IN ORGANOMETALLIC CHEMISTRY 2008. [DOI: 10.1016/s0065-3055(07)56003-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
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Mader EA, Davidson ER, Mayer JM. Large ground-state entropy changes for hydrogen atom transfer reactions of iron complexes. J Am Chem Soc 2007; 129:5153-66. [PMID: 17402735 PMCID: PMC2628630 DOI: 10.1021/ja0686918] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reported herein are the hydrogen atom transfer (HAT) reactions of two closely related dicationic iron tris(alpha-diimine) complexes. FeII(H2bip) (iron(II) tris[2,2'-bi-1,4,5,6-tetrahydropyrimidine]diperchlorate) and FeII(H2bim) (iron(II) tris[2,2'-bi-2-imidazoline]diperchlorate) both transfer H* to TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) to yield the hydroxylamine, TEMPO-H, and the respective deprotonated iron(III) species, FeIII(Hbip) or FeIII(Hbim). The ground-state thermodynamic parameters in MeCN were determined for both systems using both static and kinetic measurements. For FeII(H2bip) + TEMPO, DeltaG degrees = -0.3 +/- 0.2 kcal mol-1, DeltaH degrees = -9.4 +/- 0.6 kcal mol-1, and DeltaS degrees = -30 +/- 2 cal mol-1 K-1. For FeII(H2bim) + TEMPO, DeltaG degrees = 5.0 +/- 0.2 kcal mol-1, DeltaH degrees = -4.1 +/- 0.9 kcal mol-1, and DeltaS degrees = -30 +/- 3 cal mol-1 K-1. The large entropy changes for these reactions, |TDeltaS degrees | = 9 kcal mol-1 at 298 K, are exceptions to the traditional assumption that DeltaS degrees approximately 0 for simple HAT reactions. Various studies indicate that hydrogen bonding, solvent effects, ion pairing, and iron spin equilibria do not make major contributions to the observed DeltaS degrees HAT. Instead, this effect arises primarily from changes in vibrational entropy upon oxidation of the iron center. Measurement of the electron-transfer half-reaction entropy, |DeltaS degrees Fe(H2bim)/ET| = 29 +/- 3 cal mol-1 K-1, is consistent with a vibrational origin. This conclusion is supported by UHF/6-31G* calculations on the simplified reaction [FeII(H2N=CHCH=NH2)2(H2bim)]2+...ONH2 left arrow over right arrow [FeII(H2N=CHCH=NH2)2(Hbim)]2+...HONH2. The discovery that DeltaS degrees HAT can deviate significantly from zero has important implications on the study of HAT and proton-coupled electron-transfer (PCET) reactions. For instance, these results indicate that free energies, rather than enthalpies, should be used to estimate the driving force for HAT when transition-metal centers are involved.
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Affiliation(s)
- Elizabeth A. Mader
- University of Washington, Campus Box 351700, Seattle, WA, 98195-1700, USA, E-mail:
| | - Ernest R. Davidson
- University of Washington, Campus Box 351700, Seattle, WA, 98195-1700, USA, E-mail:
| | - James M. Mayer
- University of Washington, Campus Box 351700, Seattle, WA, 98195-1700, USA, E-mail:
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