A Pseudotetrahedral Uranium(V) Complex
Abstract
A series of uranium amides were synthesized from N,N,N-cyclohexyl(trimethylsilyl)lithium amide [Li][N(TMS)Cy] and uranium tetrachloride to give U(NCySiMe3)x(Cl)4–x, where x = 2, 3, or 4. The diamide was then isolated as a bimetallic, bridging lithium chloride adduct ((UCl2(NCyTMS)2)2-LiCl(THF)2), and the tris(amide) was isolated as the lithium chloride adduct of the monometallic species (UCl(NCyTMS)3-LiCl(THF)2). The tetraamide complex was isolated as the four-coordinate pseudotetrahedron. Cyclic voltammetry revealed an easily accessible reversible oxidation wave, and upon chemical oxidation, the UV amido cation was isolated in near-quantitative yields. The synthesis of this family of compounds allows a direct comparison of the electronic structure and properties of isostructural UIV and UV tetraamide complexes. Spectroscopic investigations consisting of UV–vis, NIR, MCD, EPR, and U L3-edge XANES, along with density functional and wave function calculations, of the four-coordinate UIV and UV complexes have been used to understand the electronic structure of these pseudotetrahedral complexes.
- Authors:
-
[1];
[1];
[4];
[1];
[1];
[1];
[1];
[1];
[3];
[1];
[1]
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. at Buffalo, NY (United States). Dept. of Chemistry
- Univ. of Rochester, NY (United States). Dept. of Chemistry
- Univ. at Buffalo, NY (United States). Dept. of Chemistry
- Publication Date:
- Research Org.:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences, and Biosciences Division; USDOE National Nuclear Security Administration (NNSA)
- OSTI Identifier:
- 1460655
- Report Number(s):
- LA-UR-18-21979
Journal ID: ISSN 0020-1669; TRN: US1901890
- Grant/Contract Number:
- AC52-06NA25396; SC0016002; SC0001136; AC02-76SF00515
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Inorganic Chemistry
- Additional Journal Information:
- Journal Volume: 57; Journal Issue: 14; Journal ID: ISSN 0020-1669
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
Citation Formats
Tondreau, Aaron M., Duignan, Thomas J., Stein, Benjamin W., Fleischauer, Valerie E., Autschbach, Jochen, Batista, Enrique R., Boncella, James M., Ferrier, Maryline G., Kozimor, Stosh A., Mocko, Veronika, Neidig, Michael L., Cary, Samantha K., and Yang, Ping. A Pseudotetrahedral Uranium(V) Complex. United States: N. p., 2018.
Web. doi:10.1021/acs.inorgchem.7b03139.
Tondreau, Aaron M., Duignan, Thomas J., Stein, Benjamin W., Fleischauer, Valerie E., Autschbach, Jochen, Batista, Enrique R., Boncella, James M., Ferrier, Maryline G., Kozimor, Stosh A., Mocko, Veronika, Neidig, Michael L., Cary, Samantha K., & Yang, Ping. A Pseudotetrahedral Uranium(V) Complex. United States. https://doi.org/10.1021/acs.inorgchem.7b03139
Tondreau, Aaron M., Duignan, Thomas J., Stein, Benjamin W., Fleischauer, Valerie E., Autschbach, Jochen, Batista, Enrique R., Boncella, James M., Ferrier, Maryline G., Kozimor, Stosh A., Mocko, Veronika, Neidig, Michael L., Cary, Samantha K., and Yang, Ping. Thu .
"A Pseudotetrahedral Uranium(V) Complex". United States. https://doi.org/10.1021/acs.inorgchem.7b03139. https://www.osti.gov/servlets/purl/1460655.
@article{osti_1460655,
title = {A Pseudotetrahedral Uranium(V) Complex},
author = {Tondreau, Aaron M. and Duignan, Thomas J. and Stein, Benjamin W. and Fleischauer, Valerie E. and Autschbach, Jochen and Batista, Enrique R. and Boncella, James M. and Ferrier, Maryline G. and Kozimor, Stosh A. and Mocko, Veronika and Neidig, Michael L. and Cary, Samantha K. and Yang, Ping},
abstractNote = {A series of uranium amides were synthesized from N,N,N-cyclohexyl(trimethylsilyl)lithium amide [Li][N(TMS)Cy] and uranium tetrachloride to give U(NCySiMe3)x(Cl)4–x, where x = 2, 3, or 4. The diamide was then isolated as a bimetallic, bridging lithium chloride adduct ((UCl2(NCyTMS)2)2-LiCl(THF)2), and the tris(amide) was isolated as the lithium chloride adduct of the monometallic species (UCl(NCyTMS)3-LiCl(THF)2). The tetraamide complex was isolated as the four-coordinate pseudotetrahedron. Cyclic voltammetry revealed an easily accessible reversible oxidation wave, and upon chemical oxidation, the UV amido cation was isolated in near-quantitative yields. The synthesis of this family of compounds allows a direct comparison of the electronic structure and properties of isostructural UIV and UV tetraamide complexes. Spectroscopic investigations consisting of UV–vis, NIR, MCD, EPR, and U L3-edge XANES, along with density functional and wave function calculations, of the four-coordinate UIV and UV complexes have been used to understand the electronic structure of these pseudotetrahedral complexes.},
doi = {10.1021/acs.inorgchem.7b03139},
journal = {Inorganic Chemistry},
number = 14,
volume = 57,
place = {United States},
year = {2018},
month = {7}
}
Free Publicly Available Full Text
Publisher's Version of Record
Other availability
Search WorldCat to find libraries that may hold this journal
Cited by: 11 works
Citation information provided by
Web of Science
Web of Science
Save to My Library
You must Sign In or Create an Account in order to save documents to your library.
Works referenced in this record:
Organic Compounds of Uranium. II. Uranium(IV) Amides, Alkoxides and Mercaptides
journal, September 1956
- Jones, R. G.; Karmas, G.; Martin, G. A.
- Journal of the American Chemical Society, Vol. 78, Issue 17
Thorium(IV) and uranium(IV) carbamates
journal, April 1974
- Bagnall, K. W.; Yanir, E.
- Journal of Inorganic and Nuclear Chemistry, Vol. 36, Issue 4
Actinide—amide complexes
journal, October 1974
- Jamerson, Jackie D.; Takats, Josef
- Journal of Organometallic Chemistry, Vol. 78, Issue 2
Crystal structure and optical and magnetic properties of tetrakis(diethylamido)uranium(IV), a five-coordinate dimeric complex in the solid state
journal, October 1976
- Reynolds, John G.; Zalkin, Allan.; Templeton, David H.
- Inorganic Chemistry, Vol. 15, Issue 10
Syntheses and crystal structures of tetrakis(diphenylamido)uranium(IV) and bis(.mu.-oxo-tris(diphenylamido)uranium(IV) lithium diethyl etherate)
journal, May 1977
- Reynolds, John G.; Zalkin, Allan.; Templeton, David H.
- Inorganic Chemistry, Vol. 16, Issue 5
Crystal structure of tetrakis[bis(N,N'-dimethylethylenediamido)uranium(IV)], tetrameric globular complex
journal, August 1977
- Reynolds, John G.; Zalkin, Allan.; Templeton, David H.
- Inorganic Chemistry, Vol. 16, Issue 8
Bis[ N , N ′-bis(trimethylsilyl)ferrocene-1,1′-diaminato]uranium(IV)
journal, August 2006
- Westmoreland, Ian; Arnold, John
- Acta Crystallographica Section E Structure Reports Online, Vol. 62, Issue 9
Redox Processes in a Uranium Bis(1,1‘-diamidoferrocene) Complex
journal, May 2007
- Monreal, Marisa J.; Carver, Colin T.; Diaconescu, Paula L.
- Inorganic Chemistry, Vol. 46, Issue 18
A Weak Interaction between Iron and Uranium in Uranium Alkyl Complexes Supported by Ferrocene Diamide Ligands
journal, March 2008
- Monreal, Marisa J.; Diaconescu, Paula L.
- Organometallics, Vol. 27, Issue 8
New UIII and UIV silylamides and an improved synthesis of NaN(SiMe2R)2 (R = Me, Ph)
journal, December 2010
- Mansell, Stephen M.; Perandones, Bernabé Fernandez; Arnold, Polly L.
- Journal of Organometallic Chemistry, Vol. 695, Issue 25-26
Tetrakis(bis(trimethylsilyl)amido)uranium(IV): Synthesis and Reactivity
journal, June 2013
- Lewis, Andrew J.; Williams, Ursula J.; Carroll, Patrick J.
- Inorganic Chemistry, Vol. 52, Issue 13
Fluorinated diarylamide complexes of uranium( iii , iv ) incorporating ancillary fluorine-to-uranium dative interactions
journal, January 2013
- Yin, Haolin; Lewis, Andrew J.; Williams, Ursula J.
- Chem. Sci., Vol. 4, Issue 2
Anomalous One-Electron Processes in the Chemistry of Uranium Nitrogen Multiple Bonds
journal, August 2014
- Mullane, Kimberly C.; Lewis, Andrew J.; Yin, Haolin
- Inorganic Chemistry, Vol. 53, Issue 17
Cerium(III) and Uranium(IV) Complexes of the 2-Fluorophenyl Trimethylsilyl Amide Ligand: C–F → Ln/An Interactions that Modulate the Coordination Spheres of f-Block Elements
journal, May 2016
- Yin, Haolin; Carroll, Patrick J.; Schelter, Eric J.
- Inorganic Chemistry, Vol. 55, Issue 11
Pentavalent uranyl complexes
journal, August 2009
- Arnold, Polly L.; Love, Jason B.; Patel, Dipti
- Coordination Chemistry Reviews, Vol. 253, Issue 15-16
Oxo ligand functionalization in the uranyl ion (UO22+)
journal, February 2010
- Fortier, Skye; Hayton, Trevor W.
- Coordination Chemistry Reviews, Vol. 254, Issue 3-4
IR Spectroelectrochemical Study on U V O 2 + Complex: First Evidence for Weakening of UO Bond Strength in Uranyl Moiety with Reduction from U(VI) to U(V)
journal, May 2003
- Mizuoka, Koichiro; Ikeda, Yasuhisa
- Inorganic Chemistry, Vol. 42, Issue 11
Molecular Structure and Electrochemical Behavior of Uranyl(VI) Complex with Pentadentate Schiff Base Ligand: Prevention of Uranyl(V) Cation−Cation Interaction by Fully Chelating Equatorial Coordination Sites
journal, March 2010
- Takao, Koichiro; Kato, Masaru; Takao, Shinobu
- Inorganic Chemistry, Vol. 49, Issue 5
Pentavalent uranium chemistry—synthetic pursuit of a rare oxidation state
journal, January 2009
- Graves, Christopher R.; Kiplinger, Jaqueline L.
- Chemical Communications, Issue 26
Recent Developments in Synthesis and Structural Chemistry of Nonaqueous Actinide Complexes
journal, October 2012
- Jones, Matthew B.; Gaunt, Andrew J.
- Chemical Reviews, Vol. 113, Issue 2
The Renaissance of Non-Aqueous Uranium Chemistry
journal, June 2015
- Liddle, Stephen T.
- Angewandte Chemie International Edition, Vol. 54, Issue 30
Recent Advances in Organoactinide Chemistry As Exemplified by Cyclopentadienyl Compounds
journal, March 2013
- Ephritikhine, Michel
- Organometallics, Vol. 32, Issue 9
Steric control of redox events in organo-uranium chemistry: synthesis and characterisation of U( v ) oxo and nitrido complexes
journal, January 2016
- Tsoureas, Nikolaos; Kilpatrick, Alexander F. R.; Inman, Christopher J.
- Chemical Science, Vol. 7, Issue 7
Tris((hexamethyldisilyl)amido)uranium(III): preparation and coordination chemistry
journal, June 1979
- Andersen, Richard A.
- Inorganic Chemistry, Vol. 18, Issue 6
A photoelectron study of pentavalent uranium imido complexes
journal, December 1987
- Brennan, John G.; Green, Jennifer C.; Redfern, Catherine M.
- Inorganica Chimica Acta, Vol. 139, Issue 1-2
Tris[bis(trimethylsilyl)amido](trimethylsilylimido)uranium(V)
journal, September 1988
- Zalkin, A.; Brennan, J. G.; Andersen, R. A.
- Acta Crystallographica Section C Crystal Structure Communications, Vol. 44, Issue 9
Uranium−Nitrogen Multiple Bonding: The Case of a Four-Coordinate Uranium(VI) Nitridoborate Complex
journal, April 2009
- Fox, Alexander R.; Cummins, Christopher C.
- Journal of the American Chemical Society, Vol. 131, Issue 16
Covalency effects on the ligand field splittings of octahedral 5f7 compounds
journal, March 1974
- Edelstein, N.; Brown, D.; Whittaker, B.
- Inorganic Chemistry, Vol. 13, Issue 3
The Inverse Trans Influence in a Family of Pentavalent Uranium Complexes
journal, June 2014
- Lewis, Andrew J.; Mullane, Kimberly C.; Nakamaru-Ogiso, Eiko
- Inorganic Chemistry, Vol. 53, Issue 13
Modified valence indices from the two-particle density matrix
journal, August 1994
- Nalewajski, Roman F.; Mrozek, Janusz
- International Journal of Quantum Chemistry, Vol. 51, Issue 4
Chemistry of uranium (V)
journal, October 1969
- Selbin, Joel; Ortego, J. D.
- Chemical Reviews, Vol. 69, Issue 5
Influence of the Nature of the Ligands on the Electronic Ground State of Organouranium(V) Compounds, Studied by Electron Paramagnetic Resonance
journal, December 1997
- Gourier, Didier; Caurant, Daniel; Berthet, Jean Claude
- Inorganic Chemistry, Vol. 36, Issue 25
EPR and Angle-Selected ENDOR Study of 5f-Ligand Interactions in the [U(η 7 -C 7 H 7 ) 2 ] - Anion, an f 1 Analogue of Uranocene
journal, June 1998
- Gourier, Didier; Caurant, Daniel; Arliguie, Thérèse
- Journal of the American Chemical Society, Vol. 120, Issue 24
Uranium Hexakisamido Complexes
journal, September 2000
- Meyer, Karsten; Mindiola, Daniel J.; Baker, Thomas A.
- Angewandte Chemie, Vol. 39, Issue 17
Small molecule activation at uranium coordination complexes: control of reactivity via molecular architecture
journal, January 2006
- Castro-Rodríguez, Ingrid; Meyer, Karsten
- Chemical Communications, Issue 13
Synthesis, Structure, and Bonding of Stable Complexes of Pentavalent Uranyl
journal, December 2009
- Nocton, Grégory; Horeglad, Pawel; Vetere, Valentina
- Journal of the American Chemical Society, Vol. 132, Issue 2
Carbon Dioxide Activation with Sterically Pressured Mid- and High-Valent Uranium Complexes
journal, September 2008
- Bart, Suzanne C.; Anthon, Christian; Heinemann, Frank W.
- Journal of the American Chemical Society, Vol. 130, Issue 37
Probing the 5f Orbital Contribution to the Bonding in a U(V) Ketimide Complex
journal, February 2012
- Seaman, Lani A.; Wu, Guang; Edelstein, Norman
- Journal of the American Chemical Society, Vol. 134, Issue 10
The Nature of the UC Double Bond: Pushing the Stability of High-Oxidation-State Uranium Carbenes to the Limit
journal, April 2013
- Cooper, Oliver J.; Mills, David P.; McMaster, Jonathan
- Chemistry - A European Journal, Vol. 19, Issue 22
Molecular and Electronic Structures of Eight-Coordinate Uranium Bipyridine Complexes: A Rare Example of a Bipy 2– Ligand Coordinated to a U 4+ Ion
journal, February 2017
- Rosenzweig, Michael W.; Heinemann, Frank W.; Maron, Laurent
- Inorganic Chemistry, Vol. 56, Issue 5
Molcas 8: New capabilities for multiconfigurational quantum chemical calculations across the periodic table : Molcas 8
journal, November 2015
- Aquilante, Francesco; Autschbach, Jochen; Carlson, Rebecca K.
- Journal of Computational Chemistry, Vol. 37, Issue 5
Magnetic Properties and Electronic Structure of Neptunyl(VI) Complexes: Wavefunctions, Orbitals, and Crystal-Field Models
journal, May 2014
- Gendron, Frédéric; Páez-Hernández, Dayán; Notter, François-Paul
- Chemistry - A European Journal, Vol. 20, Issue 26
Orbitals for Analyzing Bonding and Magnetism of Heavy-Metal Complexes
journal, September 2015
- Autschbach, Jochen
- Comments on Inorganic Chemistry, Vol. 36, Issue 4
Investigation of the Electronic Ground States for a Reduced Pyridine(diimine) Uranium Series: Evidence for a Ligand Tetraanion Stabilized by a Uranium Dimer
journal, April 2015
- Anderson, Nickolas H.; Odoh, Samuel O.; Williams, Ursula J.
- Journal of the American Chemical Society, Vol. 137, Issue 14
Examining the Effects of Ligand Variation on the Electronic Structure of Uranium Bis(imido) Species
journal, October 2016
- Kiernicki, John J.; Ferrier, Maryline G.; Lezama Pacheco, Juan S.
- Journal of the American Chemical Society, Vol. 138, Issue 42
Organometallic Uranium(V)−Imido Halide Complexes: From Synthesis to Electronic Structure and Bonding
journal, April 2008
- Graves, Christopher R.; Yang, Ping; Kozimor, Stosh A.
- Journal of the American Chemical Society, Vol. 130, Issue 15
Investigations of the Electronic Structure of Arene-Bridged Diuranium Complexes
journal, January 2013
- Vlaisavljevich, Bess; Diaconescu, Paula L.; Lukens, Wayne L.
- Organometallics, Vol. 32, Issue 5
Polarization Dependent High Energy Resolution X-ray Absorption Study of Dicesium Uranyl Tetrachloride
journal, December 2014
- Vitova, Tonya; Green, Jennifer C.; Denning, Robert G.
- Inorganic Chemistry, Vol. 54, Issue 1
Comparative Study of f-Element Electronic Structure across a Series of Multimetallic Actinide and Lanthanoid-Actinide Complexes Possessing Redox-Active Bridging Ligands
journal, February 2010
- Schelter, Eric J.; Wu, Ruilian; Veauthier, Jacqueline M.
- Inorganic Chemistry, Vol. 49, Issue 4
Electrochemical and Spectroscopic Evidence on the One-Electron Reduction of U(VI) to U(V) on Magnetite
journal, April 2015
- Yuan, Ke; Ilton, Eugene S.; Antonio, Mark R.
- Environmental Science & Technology, Vol. 49, Issue 10
Synthesis, Characterization, and Multielectron Reduction Chemistry of Uranium Supported by Redox-Active α-Diimine Ligands
journal, October 2011
- Kraft, Steven J.; Williams, Ursula J.; Daly, Scott R.
- Inorganic Chemistry, Vol. 50, Issue 20
Oxidation State Delineation via U L III -Edge XANES in a Series of Isostructural Uranium Coordination Complexes
journal, April 2012
- Kosog, Boris; La Pierre, Henry S.; Denecke, Melissa A.
- Inorganic Chemistry, Vol. 51, Issue 14
Convenient Synthesis, Structure, and Reactivity of (C 5 Me 5 )U(CH 2 C 6 H 5 ) 3 : A Simple Strategy for the Preparation of Monopentamethylcyclopentadienyl Uranium(IV) Complexes
journal, December 2002
- Kiplinger, Jaqueline L.; Morris, David E.; Scott, Brian L.
- Organometallics, Vol. 21, Issue 26
Synthesis and Structural Characterization of Magnesium Amide Complexes Containing −N[(R)(SiMe 3 )] Ligands
journal, February 2005
- Tang, Yongjun; Zakharov, Lev N.; Rheingold, Arnold L.
- Organometallics, Vol. 24, Issue 5
Selective oxidants for organometallic compounds containing a stabilising anion of highly reactive cations: (3,5(CF3)2C6H3)4B−)Cp2Fe+ and (3,5(CF3)2C6H3)4B−)Cp*2Fe+
journal, April 2000
- Chávez, Ivonne; Alvarez-Carena, Angel; Molins*, Elies
- Journal of Organometallic Chemistry, Vol. 601, Issue 1
A short history of SHELX
journal, December 2007
- Sheldrick, George M.
- Acta Crystallographica Section A Foundations of Crystallography, Vol. 64, Issue 1, p. 112-122
SHELXT – Integrated space-group and crystal-structure determination
journal, January 2015
- Sheldrick, George M.
- Acta Crystallographica Section A Foundations and Advances, Vol. 71, Issue 1, p. 3-8
OLEX2 : a complete structure solution, refinement and analysis program
journal, January 2009
- Dolomanov, Oleg V.; Bourhis, Luc J.; Gildea, Richard J.
- Journal of Applied Crystallography, Vol. 42, Issue 2
ATHENA , ARTEMIS , HEPHAESTUS : data analysis for X-ray absorption spectroscopy using IFEFFIT
journal, June 2005
- Ravel, B.; Newville, M.
- Journal of Synchrotron Radiation, Vol. 12, Issue 4
Relativistic regular two‐component Hamiltonians
journal, September 1993
- Lenthe, E. van; Baerends, E. J.; Snijders, J. G.
- The Journal of Chemical Physics, Vol. 99, Issue 6
Generalized Gradient Approximation Made Simple
journal, October 1996
- Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
- Physical Review Letters, Vol. 77, Issue 18, p. 3865-3868
Chemistry with ADF
journal, January 2001
- te Velde, G.; Bickelhaupt, F. M.; Baerends, E. J.
- Journal of Computational Chemistry, Vol. 22, Issue 9, p. 931-967
Optimized Slater-type basis sets for the elements 1-118
journal, May 2003
- Van Lenthe, E.; Baerends, E. J.
- Journal of Computational Chemistry, Vol. 24, Issue 9
Conductor-like Screening Model for Real Solvents: A New Approach to the Quantitative Calculation of Solvation Phenomena
journal, February 1995
- Klamt, Andreas
- The Journal of Physical Chemistry, Vol. 99, Issue 7
The generalized Douglas–Kroll transformation
journal, November 2002
- Wolf, Alexander; Reiher, Markus; Hess, Bernd Artur
- The Journal of Chemical Physics, Vol. 117, Issue 20
Main Group Atoms and Dimers Studied with a New Relativistic ANO Basis Set
December 2003
- Roos, Björn O.; Lindh, Roland; Malmqvist, Per-Åke
New relativistic ANO basis sets for actinide atoms
journal, June 2005
- Roos, Björn O.; Lindh, Roland; Malmqvist, Per-Åke
- Chemical Physics Letters, Vol. 409, Issue 4-6
A complete active space SCF method (CASSCF) using a density matrix formulated super-CI approach
journal, May 1980
- Roos, Björn O.; Taylor, Peter R.; Sigbahn, Per E. M.
- Chemical Physics, Vol. 48, Issue 2
The restricted active space (RAS) state interaction approach with spin–orbit coupling
journal, May 2002
- Malmqvist, Per Åke; Roos, Björn O.; Schimmelpfennig, Bernd
- Chemical Physics Letters, Vol. 357, Issue 3-4
An Alternative Approach to the g-Matrix: Theory and Applications
journal, June 2006
- Bolvin, Hélène
- ChemPhysChem, Vol. 7, Issue 7
Calculation of EPR g Tensors for Transition-Metal Complexes Based on Multiconfigurational Perturbation Theory (CASPT2)
journal, August 2007
- Vancoillie, Steven; Malmqvist, Per-Åke; Pierloot, Kristine
- ChemPhysChem, Vol. 8, Issue 12
Theoretical Description of the Structure and Magnetic Properties of Nitroxide−Cu(II)−Nitroxide Spin Triads by Means of Multiconfigurational Ab Initio Calculations
journal, May 2009
- Vancoillie, Steven; Rulíšek, Lubomír; Neese, Frank
- The Journal of Physical Chemistry A, Vol. 113, Issue 21
Ab initio calculation of anisotropic magnetic properties of complexes. I. Unique definition of pseudospin Hamiltonians and their derivation
journal, August 2012
- Chibotaru, L. F.; Ungur, L.
- The Journal of Chemical Physics, Vol. 137, Issue 6