Isomerism and dynamic behavior of bridging phosphaalkynes bound to a dicopper complex
Abstract
A dicopper complex featuring a symmetrically bridging nitrile ligand and supported by a binucleating naphthyridine-based ligand, [Cu2(μ-η1:η1-MeCN)DPFN](NTf2)2, was treated with phosphaalkynes (RC$$\equiv$$P, isoelectronic analogues of nitriles) to yield dicopper complexes that exhibit phosphaalkynes in rare μ-η2:η2 binding coordination modes. X-ray crystallography revealed that these unusual “tilted” structures exist in two isomeric forms (R “up” vs. R “sideways”), depending on the steric profile of the phosphaalkyne's alkyl group (R = Me, Ad, or tBu). Only one isomer is observed in both solution and the solid state for R = Me (sideways) and tBu (up). With intermediate steric bulk (R = Ad), the energy difference between the two geometries is small enough that both are observed in solution, and NMR spectroscopy and computations indicate that the solid-state structure corresponds to the minor isomer observed in solution. Meanwhile, treatment of [Cu2(μ-η1:η1-MeCN)DPFN](NTf2)2 with 2-butyne affords [Cu2(μ-η2:η2-(MeC$$\equiv$$CMe))DPFN](NTf2)2: its similar ligand geometry demonstrates that the tilted μ-η2:η2 binding mode is not limited to phosphaalkynes but reflects a more general trend, which can be rationalized via an NBO analysis showing maximization of π-backbonding.
- Authors:
-
- Department of Chemistry, University of California, Berkeley, Berkeley, USA, Chemical Sciences Division
- Department of Chemistry, University of California, Berkeley, Berkeley, USA
- Institut für Anorganische Chemie, Universität Regensburg, 93040 Regensburg, Germany
- Publication Date:
- Research Org.:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division; National Institutes of Health (NIH); Alexander von Humboldt Foundation; National Science Foundation (NSF)
- OSTI Identifier:
- 1581662
- Alternate Identifier(s):
- OSTI ID: 1615295
- Grant/Contract Number:
- AC02-05CH11231; S10-RR027172; S10OD023532; DGE 1106400; SRR023679A; 1S10RR016634-01; GM68933
- Resource Type:
- Published Article
- Journal Name:
- Chemical Science
- Additional Journal Information:
- Journal Name: Chemical Science Journal Volume: 11 Journal Issue: 6; Journal ID: ISSN 2041-6520
- Publisher:
- Royal Society of Chemistry
- Country of Publication:
- United Kingdom
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Citation Formats
Nicolay, Amélie, Ziegler, Micah S., Small, David W., Grünbauer, Rebecca, Scheer, Manfred, and Tilley, T. Don. Isomerism and dynamic behavior of bridging phosphaalkynes bound to a dicopper complex. United Kingdom: N. p., 2019.
Web. doi:10.1039/C9SC05835D.
Nicolay, Amélie, Ziegler, Micah S., Small, David W., Grünbauer, Rebecca, Scheer, Manfred, & Tilley, T. Don. Isomerism and dynamic behavior of bridging phosphaalkynes bound to a dicopper complex. United Kingdom. doi:10.1039/C9SC05835D.
Nicolay, Amélie, Ziegler, Micah S., Small, David W., Grünbauer, Rebecca, Scheer, Manfred, and Tilley, T. Don. Thu .
"Isomerism and dynamic behavior of bridging phosphaalkynes bound to a dicopper complex". United Kingdom. doi:10.1039/C9SC05835D.
@article{osti_1581662,
title = {Isomerism and dynamic behavior of bridging phosphaalkynes bound to a dicopper complex},
author = {Nicolay, Amélie and Ziegler, Micah S. and Small, David W. and Grünbauer, Rebecca and Scheer, Manfred and Tilley, T. Don},
abstractNote = {A dicopper complex featuring a symmetrically bridging nitrile ligand and supported by a binucleating naphthyridine-based ligand, [Cu2(μ-η1:η1-MeCN)DPFN](NTf2)2, was treated with phosphaalkynes (RC$\equiv$P, isoelectronic analogues of nitriles) to yield dicopper complexes that exhibit phosphaalkynes in rare μ-η2:η2 binding coordination modes. X-ray crystallography revealed that these unusual “tilted” structures exist in two isomeric forms (R “up” vs. R “sideways”), depending on the steric profile of the phosphaalkyne's alkyl group (R = Me, Ad, or tBu). Only one isomer is observed in both solution and the solid state for R = Me (sideways) and tBu (up). With intermediate steric bulk (R = Ad), the energy difference between the two geometries is small enough that both are observed in solution, and NMR spectroscopy and computations indicate that the solid-state structure corresponds to the minor isomer observed in solution. Meanwhile, treatment of [Cu2(μ-η1:η1-MeCN)DPFN](NTf2)2 with 2-butyne affords [Cu2(μ-η2:η2-(MeC$\equiv$CMe))DPFN](NTf2)2: its similar ligand geometry demonstrates that the tilted μ-η2:η2 binding mode is not limited to phosphaalkynes but reflects a more general trend, which can be rationalized via an NBO analysis showing maximization of π-backbonding.},
doi = {10.1039/C9SC05835D},
journal = {Chemical Science},
number = 6,
volume = 11,
place = {United Kingdom},
year = {2019},
month = {12}
}
DOI: 10.1039/C9SC05835D
Web of Science
Works referenced in this record:
Comprehensive Thermochemical Benchmark Set of Realistic Closed-Shell Metal Organic Reactions
journal, March 2018
- Dohm, Sebastian; Hansen, Andreas; Steinmetz, Marc
- Journal of Chemical Theory and Computation, Vol. 14, Issue 5
Novel Copper(I) Complexes Containing 1,1‘-Bis(diphenylphosphino)ferrocene (dppf) as a Chelate and Bridging Ligand: Synthesis of Tetrabridged Dicopper(I) Complexes [Cu 2 (μ-η 1 -C⋮R) 2 (μ-dppf) 2 ] and X-ray Crystal Structure of [Cu 2 (μ-η 1 -C⋮CC 6 H 4 CH 3 -4) 2 (μ-dppf) 2 ]
journal, February 1999
- Díez, Josefina; Gamasa, M. Pilar; Gimeno, José
- Organometallics, Vol. 18, Issue 4
Unhindered phosphaalkenes and phosphaalkynes in stable condition from a vacuum multistep sequence.
journal, January 1986
- Pellerin, Bruno; Denis, Jean-Marc; Perrocheau, Jacques
- Tetrahedron Letters, Vol. 27, Issue 47
Group 1B organometallic chemistry. Part 25. Crystal and molecular structure of 1,2,3;1,4,5;2,3,6;4,5,6-tetrakis-µ 3 -2-dimethylaminophenyl-2,5;3,4-bis-µ 2 -4-tolylethynyl-octahedro-hexacopper( I )
journal, January 1978
- ten Hoedt, Richard W. M.; Noltes, Jan G.; van Koten, Gerard
- J. Chem. Soc., Dalton Trans., Issue 12
Di- tert -butyldiphosphatetrahedrane: Catalytic Synthesis of the Elusive Phosphaalkyne Dimer
journal, October 2019
- Hierlmeier, Gabriele; Coburger, Peter; Bodensteiner, Michael
- Angewandte Chemie International Edition, Vol. 58, Issue 47
Bridged hydrocarbyl or hydrocarbon binuclear transition metal complexes: classification, structures, and chemistry
journal, April 1983
- Holton, John; Lappert, Michael F.; Pearce, Ronald
- Chemical Reviews, Vol. 83, Issue 2
Preparation and Solid-State Characterization of Mixed-Ligand Coordination/Organometallic Oligomers and Polymers of Copper(I) and Silver(I) Using Diphosphine and Mono- and Diisocyanide Ligands
journal, May 2004
- Fournier, Éric; Lebrun, Frédéric; Drouin, Marc
- Inorganic Chemistry, Vol. 43, Issue 10
The microwave spectrum of 1-phosphapropyne, CH3CP
journal, August 1979
- Kroto, H. W.; Nixon, J. F.; Simmons, N. P. C.
- Journal of Molecular Spectroscopy, Vol. 77, Issue 2
Dicopper Cu(I)Cu(I) and Cu(I)Cu(II) Complexes in Copper-Catalyzed Azide–Alkyne Cycloaddition
journal, April 2017
- Ziegler, Micah S.; Lakshmi, K. V.; Tilley, T. Don
- Journal of the American Chemical Society, Vol. 139, Issue 15
(CH3)3SiCP, ein silylfunktionelles phospha-alkin
journal, January 1981
- Appel, Rolf; Westerhaus, Axel
- Tetrahedron Letters, Vol. 22, Issue 23
Cleavage of a phosphorus carbon triple bond in the reaction of 2,2-dimethylpropylidynephosphine with [Os3(CO)10(μ3-η1:η2:η1-C2Me)]
journal, January 1998
- Nowotny, Mathias; Johnson, Brian F. G.; Nixon, John F.
- Chemical Communications, Issue 20
Chemie polyfunktioneller Molek�le. 119 [1] Tetracarbonyl-dicobalt-tetrahedran-Komplexe mit den Liganden Bis(diphenyl-phosphanyl)amin, 2-Butin-1,4-diol und tert-Butylphosphaacetylen ? Kristallstrukturanalyse des Phosphaalkin-Derivats
journal, February 1996
- Pohl, Diana; Ellermann, Jochen; Moll, Matthias
- Zeitschrift f�r anorganische und allgemeine Chemie, Vol. 622, Issue 2
Addition of a Phosphaalkyne to Metal-Metal Multiple Bonds
journal, May 1983
- Becker, Gerd; Herrmann, Wolfgang A.; Kalcher, Willibald
- Angewandte Chemie International Edition in English, Vol. 22, Issue 5
A Series of Dinuclear Copper Complexes Bridged by Phosphanylbipyridine Ligands: Synthesis, Structural Characterization and Electrochemistry
journal, January 2013
- Lilio, Alyssia M.; Grice, Kyle A.; Kubiak, Clifford P.
- European Journal of Inorganic Chemistry, Vol. 2013, Issue 22-23
Elimination and Addition at the Phosphorus-Carbon pπ-pπ Bond
journal, February 1981
- Appel, Rolf; Maier, Günther; Reisenauer, Hans Peter
- Angewandte Chemie International Edition in English, Vol. 20, Issue 2
Cuprophilic Interactions in and between Molecular Entities
journal, May 2019
- Harisomayajula, N. V. Satyachand; Makovetskyi, Serhii; Tsai, Yi‐Chou
- Chemistry – A European Journal, Vol. 25, Issue 38
A novel copper(I) complex with bridging alkyne ligands. The synthesis and structural characterization of [Cu4(O2CCF3)4(.mu.-EtC.tplbond.CEt)2]
journal, March 1989
- Reger, Daniel L.; Huff, Mark F.; Wolfe, Thomas A.
- Organometallics, Vol. 8, Issue 3
Cooperative Catalysis with First-Row Late Transition Metals
journal, September 2011
- van der Vlugt, Jarl Ivar; de Bruin, Bas
- European Journal of Inorganic Chemistry, Vol. 2012, Issue 3, p. 363-375
The Elephant in the Room of Density Functional Theory Calculations
journal, March 2017
- Jensen, Stig Rune; Saha, Santanu; Flores-Livas, José A.
- The Journal of Physical Chemistry Letters, Vol. 8, Issue 7
The Hurtley reaction. 2. Novel complexes of disubstituted acetylenes with copper(I) benzoates having a reactive ortho carbon-chlorine or carbon-bromine bond. X-ray structural characterization of tetrakis(2-chlorobenzoato)bis(diethyl acetylenedicarboxylate)tetracopper(I)
journal, November 1989
- Aalten, Henk L.; Van Koten, Gerard; Riethorst, Ed
- Inorganic Chemistry, Vol. 28, Issue 22
Relativistic Force Field: Parametric Computations of Proton–Proton Coupling Constants in 1 H NMR Spectra
journal, August 2014
- Kutateladze, Andrei G.; Mukhina, Olga A.
- The Journal of Organic Chemistry, Vol. 79, Issue 17
NBO 6.0 : Natural bond orbital analysis program
journal, March 2013
- Glendening, Eric D.; Landis, Clark R.; Weinhold, Frank
- Journal of Computational Chemistry, Vol. 34, Issue 16
The basicity of phosphines
journal, March 1982
- Allman, Tim; Goel, Ram G.
- Canadian Journal of Chemistry, Vol. 60, Issue 6
Isolation and characterisation of the first stable diphospha-allene: P,P′-bis(2,4,6-tri-t-butylphenyl)-1,3-diphospha-allene
journal, January 1984
- Yoshifuji, Masaaki; Toyota, Kozo; Inamoto, Naoki
- J. Chem. Soc., Chem. Commun., Issue 11
Isolated Monomeric and Dimeric Mixed Diorganocuprates Based on the Size-Controllable Bulky “Rind” Ligands
journal, December 2009
- Ito, Mikinao; Hashizume, Daisuke; Fukunaga, Takeo
- Journal of the American Chemical Society, Vol. 131, Issue 50
A Simple Route to Kinetically Unstabilized Phosphaalkynes
journal, November 2001
- Guillemin, Jean-Claude; Janati, Tajdine; Denis, Jean-Marc
- The Journal of Organic Chemistry, Vol. 66, Issue 23
Copper Active Sites in Biology
journal, January 2014
- Solomon, Edward I.; Heppner, David E.; Johnston, Esther M.
- Chemical Reviews, Vol. 114, Issue 7
1H-1,3-azaphosphole - neue phosphaaromaten
journal, January 1986
- Heinicke, J.
- Tetrahedron Letters, Vol. 27, Issue 47
Phosphaalkynes—Syntheses, Reactions, Coordination Behavior[New Synthetic Methods(73)]
journal, November 1988
- Regitz, Manfred; Binger, Paul
- Angewandte Chemie International Edition in English, Vol. 27, Issue 11
Photoelectron spectra of the phospha-alkynes: 3,3-dimethyl-1-phosphabutyne Bu t CP and phenylphosphaethyne, PhCP
journal, January 1983
- Laurent, James C. T. R. Burckett-St.; King, Michael A.; Kroto, Harold W.
- J. Chem. Soc., Dalton Trans., Issue 4
Progress and Perspectives of Electrochemical CO 2 Reduction on Copper in Aqueous Electrolyte
journal, April 2019
- Nitopi, Stephanie; Bertheussen, Erlend; Scott, Soren B.
- Chemical Reviews, Vol. 119, Issue 12
Cyclopentadienyl and Alkynyl Copper(I ) Derivatives with the [{Ti(η 5 -C 5 Me 5 )(μ-NH)} 3 (μ 3 -N)] Metalloligand
journal, December 2010
- Martínez-Espada, Noelia; Mena, Miguel; Mosquera, Marta E. G.
- Organometallics, Vol. 29, Issue 24
High-Throughput in Silico Structure Validation and Revision of Halogenated Natural Products Is Enabled by Parametric Corrections to DFT-Computed 13 C NMR Chemical Shifts and Spin–Spin Coupling Constants
journal, March 2017
- Kutateladze, Andrei G.; Reddy, D. Sai
- The Journal of Organic Chemistry, Vol. 82, Issue 7
Effect of the damping function in dispersion corrected density functional theory
journal, March 2011
- Grimme, Stefan; Ehrlich, Stephan; Goerigk, Lars
- Journal of Computational Chemistry, Vol. 32, Issue 7
Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy
journal, January 2005
- Weigend, Florian; Ahlrichs, Reinhart
- Physical Chemistry Chemical Physics, Vol. 7, Issue 18, p. 3297-3305
(2,6-Dimethylphenyl)(9-fluorenyliden)phosphan
journal, March 1984
- Van Knaap, Theodorus A. Der; Bickelhaupt, Friedrich
- Chemische Berichte, Vol. 117, Issue 3
Catalytic Azoarene Synthesis from Aryl Azides Enabled by a Dinuclear Ni Complex
journal, February 2018
- Powers, Ian G.; Andjaba, John M.; Luo, Xuyi
- Journal of the American Chemical Society, Vol. 140, Issue 11
Multimetallic Catalysis Based on Heterometallic Complexes and Clusters
journal, November 2014
- Buchwalter, Paulin; Rosé, Jacky; Braunstein, Pierre
- Chemical Reviews, Vol. 115, Issue 1
Organonitrile complexes of transition metals
journal, June 1977
- N. Storhoff, Bruce; C. Lewis Jr., Huntley
- Coordination Chemistry Reviews, Vol. 23, Issue 1
The calculation of force constants and normal coordinates—V constrained force fields for a series of methyl and dimethyl compounds of 3-fold symmetry
journal, July 1964
- Duncan, J. L.
- Spectrochimica Acta, Vol. 20, Issue 7
Computed Spin−Spin Coupling Constants ( 1 J X - Y ) in Molecules H m X−YH n for X and Y = 13 C, 15 N, and 31 P: Comparisons with Experiment and Insights into the Signs of 1 J X - Y
journal, April 2004
- Del Bene, Janet E.; Elguero, José; Alkorta, Ibon
- The Journal of Physical Chemistry A, Vol. 108, Issue 16
π Back-Bonding in Dibenzyl-β-diketiminato Copper Olefin Complexes
journal, December 2009
- Oguadinma, Paul O.; Schaper, Frank
- Organometallics, Vol. 28, Issue 23
Computational NMR Methods in the Stereochemical Analysis of Organic Compounds: Are Proton or Carbon NMR Chemical Shift Data More Discriminating?: Computational NMR for the Analysis of Organic Compounds
journal, January 2015
- Chini, Maria Giovanna; Riccio, Raffaele; Bifulco, Giuseppe
- European Journal of Organic Chemistry, Vol. 2015, Issue 6
Copper–Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity
journal, January 2017
- Elwell, Courtney E.; Gagnon, Nicole L.; Neisen, Benjamin D.
- Chemical Reviews, Vol. 117, Issue 3
Aryl Group Transfer from Tetraarylborato Anions to an Electrophilic Dicopper(I) Center and Mixed-Valence μ-Aryl Dicopper(I,II) Complexes
journal, May 2016
- Ziegler, Micah S.; Levine, Daniel S.; Lakshmi, K. V.
- Journal of the American Chemical Society, Vol. 138, Issue 20
Synthesis, Photophysical Properties, and Computational Analysis of Di- and Tetranuclear Alkyne Complexes of Copper(I) Supported by a Highly Fluorinated Pyrazolate
journal, October 2018
- Parasar, Devaborniny; Almotawa, Ruaa M.; Jayaratna, Naleen B.
- Organometallics, Vol. 37, Issue 21
A Simple Route to the 1-Aza-3-Phosphaallyl System: Structure of a Dimeric Lithium Complex and Protonation to Give the First NH2-Substituted Phosphaalkene
journal, November 1995
- Paasch, Karin; Nieger, Martin; Niecke, Edgar
- Angewandte Chemie International Edition in English, Vol. 34, Issue 21
Unusually Coordinated Phosphorus Compounds; 7 1 . Adamant-1-ylmethylidynephosphine, A New, Stable Phosphaalkyne
journal, January 1986
- Allspach, T.; Regitz, M.; Becker, G.
- Synthesis, Vol. 1986, Issue 01
Copper-Catalyzed [3+2] Cycloaddition Reactions of Isocyanoacetates with Phosphaalkynes to Prepare 1,3-Azaphospholes
journal, December 2018
- Liang, Wenbin; Nakajima, Kazunari; Sakata, Ken
- Angewandte Chemie International Edition, Vol. 58, Issue 4
Isolation of bis(copper) key intermediates in Cu-catalyzed azide-alkyne “click reaction”
journal, June 2015
- Jin, Liqun; Tolentino, Daniel R.; Melaimi, Mohand
- Science Advances, Vol. 1, Issue 5
Reactions of [Fe2(CO)6(μ-CO)(μ-dppm)], with PhCCH and the phospha-alkyne, tBuCP. Crystal and molecular structures of the four diiron complexes [Fe2(CO) 4(μ-CO)(μ-dppm)2], [Fe2,(CO)5,(μ-dppm)(μ-η2-CHC(CO)Ph], [Fe2,(CO)4,(μ-CO)(μ-dppm)(μ-η2-tBuCP)], and [Fe2(CO)5 (μ-dppm)(μ-gh2-PC(CO)tBu)]
journal, December 1993
- Hitchcock, Peter B.; Madden, Timothy J.; Nixon, John F.
- Journal of Organometallic Chemistry, Vol. 463, Issue 1-2
Metal–Metal Bonds in Catalysis
journal, December 2016
- Powers, Ian G.; Uyeda, Christopher
- ACS Catalysis, Vol. 7, Issue 2
Copper–NHC complexes in catalysis
journal, June 2015
- Lazreg, Faïma; Nahra, Fady; Cazin, Catherine S. J.
- Coordination Chemistry Reviews, Vol. 293-294
Main group and transition metal-mediated phosphaalkyne oligomerizations
journal, July 2014
- Chirila, Andrei; Wolf, Robert; Chris Slootweg, J.
- Coordination Chemistry Reviews, Vol. 270-271
Dicopper μ-Oxo, μ-Nitrosyl Complex from the Activation of NO or Nitrite at a Dicopper Center
journal, May 2019
- Tao, Wenjie; Bower, Jamey K.; Moore, Curtis E.
- Journal of the American Chemical Society, Vol. 141, Issue 26
Bis(alkynyl) transition metal complexes, R1CC[M]CCR2, as organometallic chelating ligands; formation of μ,η1(2)-alkynyl-bridged binuclear and oligonuclear complexes
journal, September 2000
- Lang, Heinrich; George, Darren S. A.; Rheinwald, Gerd
- Coordination Chemistry Reviews, Vol. 206-207
Dinucleating Naphthyridine-Based Ligand for Assembly of Bridged Dicopper(I) Centers: Three-Center Two-Electron Bonding Involving an Acetonitrile Donor
journal, October 2011
- Davenport, Timothy C.; Tilley, T. Don
- Angewandte Chemie International Edition, Vol. 50, Issue 51
Phosphatriafulvenes - phosphaalkenes with inverse electron density
journal, January 1989
- Fuchs, Eberhard P. O.; Heydt, Heinrich; Regitz, Manfred
- Tetrahedron Letters, Vol. 30, Issue 38
Correction to Aerobic Copper-Catalyzed Organic Reactions
journal, September 2013
- Allen, Scott E.; Walvoord, Ryan R.; Padilla-Salinas, Rosaura
- Chemical Reviews, Vol. 114, Issue 1
Dicopper(I) tropocoronands: synthesis, x-ray crystal structure, and spectral properties of neutral binuclear copper(I) complexes bridged by symmetrically substituted alkynes
journal, November 1985
- Villacorte, Gilberto M.; Gibson, Dan; Williams, Ian D.
- Journal of the American Chemical Society, Vol. 107, Issue 23
Dinuclear Copper(I) Complexes of Phenanthrolinyl-Functionalized NHC Ligands
journal, September 2013
- Liu, Bo; Chen, Congyan; Zhang, Yuejiao
- Organometallics, Vol. 32, Issue 19
The first complexes and cyclodimerisations of methylphosphaalkyne (PCMe)
journal, January 2006
- Jones, Cameron; Schulten, Christian; Stasch, Andreas
- Dalton Trans., Issue 31
Improving the Accuracy of Computed 13 C NMR Shift Predictions by Specific Environment Error Correction: Fragment Referencing
journal, October 2013
- Andrews, Keith G.; Spivey, Alan C.
- The Journal of Organic Chemistry, Vol. 78, Issue 22
Synthesis and reactivity of binuclear copper(I) complexes of 2-(diphenylphosphino)-6-(pyrazol-1-yl)pyridine (L1). Crystal structures of [Cu2(μ-L1)2(MeCN)2][ClO4]2, [Cu2(μ-L1)2(μ-η1-CCPh)][ClO4]· CHCl3·H2O and [Cu2(μ-L1)2(μ-Cl)][ClO4]·H2O
journal, January 1998
- Kuang, Shan-Ming; Zhang, Zheng-Zhi; Wang, Qi-Guang
- Journal of the Chemical Society, Dalton Transactions, Issue 7
C,C-Diacetylenic phosphaalkenes in palladium-catalyzed cross-coupling reactions
journal, January 2011
- Öberg, Elisabet; Geng, Xue-Li; Santoni, Marie-Pierre
- Organic & Biomolecular Chemistry, Vol. 9, Issue 18