Leslie J. Murray - Cochemist

Correlating Bridging Ligand with Properties of Ligand-Templated [MnII3X3]3+ Clusters (X = Br–, Cl–, H–, MeO–)

Co-reporter:Kevin J. Anderton, David M. Ermert, Pedro A. Quintero, Mackenzie W. Turvey, Majed S. Fataftah, Khalil A. Abboud, Mark W. Meisel, Erik Čižmár, and Leslie J. Murray

Inorganic Chemistry October 2, 2017 Volume 56(Issue 19) pp:12012-12012

Publication Date(Web):September 18, 2017

DOI:10.1021/acs.inorgchem.7b02004

Polynuclear manganese compounds have garnered interest as mimics and models of the water oxidizing complex (WOC) in photosystem II and as single molecule magnets. Molecular systems in which composition can be correlated to physical phenomena, such as magnetic exchange interactions, remain few primarily because of synthetic limitations. Here, we report the synthesis of a family of trimanganese(II) complexes of the type Mn3X3L (X = Cl–, H–, and MeO–) where L3– is a tris(β-diketiminate) cyclophane. The tri(chloride) complex (2) is structurally similar to the reported tri(bromide) complex (1) with the Mn3X3 core having a ladder-like arrangement of alternating M–X rungs, whereas the tri(μ-hydride) (3) and tri(μ-methoxide) (4) complexes contain planar hexagonal cores. The hydride and methoxide complexes are synthesized in good yield (48% and 56%) starting with the bromide complex employing a metathesis-like strategy. Compounds 2–4 were characterized by combustion analysis, X-ray crystallography, X-band EPR spectroscopy, SQUID magnetometry, and infrared and UV–visible spectroscopy. Magnetic susceptibility measurements indicate that the Mn3 clusters in 2–4 are antiferromagnetically coupled, and the spin ground state of the compounds (S = 3/2 (1, 2) or S = 1/2 (3, 4)) is correlated to the identity of the bridging ligand and structural arrangement of the Mn3X3 core (X = Br, Cl, H, OCH3). Electrochemical experiments on isobutyronitrile solutions of 3 and 4 display broad irreversible oxidations centered at 0.30 V.

A [3Fe–3S]3+ cluster with exclusively μ-sulfide donors

Co-reporter:Yousoon Lee, Ie-Rang Jeon, Khalil A. Abboud, Ricardo García-Serres, Jason Shearer and Leslie J. Murray

Chemical Communications 2016 vol. 52(Issue 6) pp:1174-1177

Publication Date(Web):25 Nov 2015

DOI:10.1039/C5CC07813J

A [3Fe–3(μ-S)]3+ cluster is reported in which each ferric center has a distorted trigonal pyramidal geometry, with an S = 1/2 ground state for the cluster and unusually anisotropic hyperfine coupling constants as determined by variable temperature magnetometry and Mössbauer spectroscopy.

A three-coordinate Fe(II) center within a [3Fe–(μ3-S)] cluster that provides an accessible coordination site

Co-reporter:Yousoon Lee, Khalil A. Abboud, Ricardo García-Serres and Leslie J. Murray

Chemical Communications 2016 vol. 52(Issue 59) pp:9295-9298

Publication Date(Web):01 Jul 2016

DOI:10.1039/C6CC04671A

A μ3-sulfide bridged triiron cluster(II,II,III) supported by a cyclophane ligand undergoes metal-based reduction to yield an all-ferrous species. The latter complex incorporates a three-coordinate iron center that provides an accessible coordination site to a solvent molecule.

Synthesis of Trinuclear Tin(II), Germanium(II), and Aluminum(III) Cyclophane Complexes

Co-reporter:David M. Ermert, Jesse B. Gordon, Khalil A. Abboud, and Leslie J. Murray

Organometallics 2016 Volume 35(Issue 21) pp:3651-3657

Publication Date(Web):October 21, 2016

DOI:10.1021/acs.organomet.6b00354

The synthesis and characterization of trinuclear GeII and SnII chlorides and a trialuminum complex supported by a trinucleating tris(β-diketiminate) cyclophane ligand (L3–) are reported. The in situ deprotonation of H3L with benzylpotassium and subsequent reaction with GeCl2·dioxane or SnCl2 afforded (GeCl)3L (1) and (SnCl)3L (2) in 42 and 60% yields, respectively. Each GeII and SnII atom is three-coordinate and exhibit pseudotrigonal pyramidal geometry as anticipated for three-coordinate divalent group 14 cations. UV/visible spectra collected on THF solutions of 1 and 2 display a bathochromic shift in the absorption from 1 to 2 (from 361 to 375 nm). Addition of AlMe3 to toluene solutions of H3L resulted in the formation of (AlMe2)2AlMe3HL (3), which possesses two NCCCN chelated AlMe2 moieties. The third β-diketimine arm remains protonated and adopts an atypical trans conformation with an AlMe3 coordinated to the solvent exposed imine N atom.

Reactivity of Hydride Bridges in High-Spin [3M–3(μ-H)] Clusters (M = FeII, CoII)

Co-reporter:Yousoon Lee; Kevin J. Anderton; Forrest T. Sloane; David M. Ermert; Khalil A. Abboud; Ricardo García-Serres

Journal of the American Chemical Society 2015 Volume 137(Issue 33) pp:10610-10617

Publication Date(Web):August 13, 2015

DOI:10.1021/jacs.5b05204

The designed [3M–3(μ-H)] clusters (M = FeII, CoII) Fe3H3L (1-H) and Co3H3L (2-H) [where L3– is a tris(β-diketiminate) cyclophane] were synthesized by treating the corresponding M3Br3L complexes with KBEt3H. From single-crystal X-ray analysis, the hydride ligands are sterically protected by the cyclophane ligand, and these complexes selectively react with CO2 over other unsaturated substrates (e.g., CS2, Me3SiCCH, C2H2, and CH3CN). The reaction of 1-H or 2-H with CO2 at room temperature yielded Fe3(OCHO)(H)2L (1-CO2) or Co3(OCHO)(H)2L (2-CO2), respectively, which evidence the differential reactivity of the hydride ligands within these complexes. The analogous reactions at elevated temperatures revealed a distinct difference in the reactivity pattern for 2-H as compared to 1-H; Fe3(OCHO)3L (1-3CO2) was generated from 1-H, while 2-H afforded only 2-CO2.

A Family of Tri- and Dimetallic Pyridine Dicarboxamide Cryptates: Unusual O,N,O-Coordination and Facile Access to Secondary Coordination Sphere Hydrogen Bonding Interactions

Co-reporter:Gary L. Guillet; Jesse B. Gordon; Gianna N. Di Francesco; Matthew W. Calkins; Erik Čižmár; Khalil A. Abboud; Mark W. Meisel; Ricardo García-Serres

Inorganic Chemistry 2015 Volume 54(Issue 6) pp:2691-2704

Publication Date(Web):February 24, 2015

DOI:10.1021/ic502873d

A series of tri- and dimetallic metal complexes of pyridine dicarboxamide cryptates are reported in which changes to the base and metal source result in diverse structure types. Addition of strong bases, such as KH or KN(SiMe3)2, followed by divalent metal halides allows direct access to trinuclear complexes in which each metal center is coordinated by a dianionic N,N,N-chelate of each arm. These complexes bind a guest K+ cation within the central cavity in a trigonal planar coordination environment. Minor changes to the solvent and equivalents of base used in the syntheses of the triiron(II) and tricobalt(II) complexes affords two trinuclear clusters with atypical O,N,O-coordination by each pyridine dicarboxamide arm; the amide carbonyl O atoms are oriented toward the interior of the cavity to coordinate to each metal center. Finally, varying the base enables the selective synthesis of dinuclear nickel(II) and copper(II) complexes in which one pyridine dicarboxamide arm remains protonated. These amide protons are at one end of a hydrogen bonding network that extends throughout the internal cavity and terminates at a metal bound hydroxide, carbonate, or bicarbonate donor. In the dinickel complex, the bicarbonate cannot be liberated as CO2 either thermally or upon sparging with N2, which differs from previously reported monometallic complexes. The carbonate or bicarbonate ligands likely arise from sequestration of atmospheric CO2 based on the observed reaction of the di(hydroxonickel) analog.

Nitride-Bridged Triiron Complex and Its Relevance to Dinitrogen Activation

Co-reporter:David M. Ermert; Jesse B. Gordon; Khalil A. Abboud

Inorganic Chemistry 2015 Volume 54(Issue 19) pp:9282-9289

Publication Date(Web):June 8, 2015

DOI:10.1021/acs.inorgchem.5b00825

Using a simple metathesis approach, the triiron(II) tribromide complex Fe3Br3L (1) reacts with tetrabutylammonium azide to afford the monoazide dibromide analogue Fe3(Br)2(N3)L (2) in high yield. The inclusion of azide was confirmed by IR spectroscopy with a ν(N3) = 2082 cm–1 as well as combustion analysis and X-ray crystallography. Heating 2 in the solid state results in the complete loss of the azide vibration in the IR spectra and the isolation of the olive-green mononitride complex Fe3(Br)2(N)L (3). Solution magnetic susceptibility measurements support that the trimetallic core within 2 is oxidized upon generation of 3 (5.07 vs 3.09 μB). Absorption maxima in the UV–visible–near-IR (NIR) spectra of 2 and 3 support the azide-to-nitride conversion, and a broad NIR absorption centered at 1117 nm is similar to that previously reported for the intervalence charge-transfer band for a mixed-valent nitridodiiron cluster. The cyclic voltammograms recorded for 3 are comparable to those of 1 with no reductive waves observed between ∼0 and −2.5 V (vs Fc/Fc+), whereas a reversible one-electron redox process is observed for Fe3(NH2)3L (4). These results suggest that intercluster cooperativity is unlikely to predominate the dinitrogen reduction mechanism when 1 is treated with KC8 under N2.

Dinitrogen Activation Upon Reduction of a Triiron(II) Complex

Co-reporter:Yousoon Lee;Forrest T. Sloane;Dr. Geneviève Blondin;Dr. Khalil A. Abboud;Dr. Ricardo García-Serres;Dr. Leslie J. Murray

Angewandte Chemie International Edition 2015 Volume 54( Issue 5) pp:1499-1503

Publication Date(Web):

DOI:10.1002/anie.201409676

Abstract

Reaction of a trinuclear iron(II) complex, Fe₃Br₃L (1), with KC₈ under N₂ leads to dinitrogen activation products (2) from which Fe₃(NH)₃L (2-1; L is a cyclophane bridged by three β-diketiminate arms) was characterized by X-ray crystallography. ¹H NMR spectra of the protonolysis product of 2 synthesized under ¹⁴N₂ and ¹⁵N₂ confirm atmospheric N₂ reduction, and ammonia is detected by the indophenol assay (yield ∼30 %). IR and Mössbauer spectroscopy, and elemental analysis on 2 and 2-1 as well as the tri(amido)triiron(II) 3 and tri(methoxo)triiron 4 congeners support our assignment of the reduction product as containing protonated N-atom bridges.

An Air- and Water-Tolerant Zinc Hydride Cluster That Reacts Selectively With CO2

Co-reporter:David M. Ermert;Dr. Ion Ghiviriga;Dr. Vincent J. Catalano;Dr. Jason Shearer;Dr. Leslie J. Murray

Angewandte Chemie International Edition 2015 Volume 54( Issue 24) pp:7047-7050

Publication Date(Web):

DOI:10.1002/anie.201501539

Abstract

The reaction of [Zn₃Cl₃L], in which L³⁻ is a tris(β-diketiminate) cyclophane, with K(sBu)₃BH afforded [Zn₃(μ-H)₃L] (2), as confirmed by NMR spectroscopy, NOESY, and X-ray crystallography. The complex 2 was air-stable and unreactive towards water, methanol, and other substrates (e.g., nitriles) at room temperature over 24 h but reacted with CO₂ (ca. 1 atm) to generate [Zn₃(μ-H)₂(μ-1,1-O₂CH)] (3). In contrast, [Zn₃(OH)₃L] (4) was found to be unreactive toward CO₂ over the course of several days at 90 °C.

An Air- and Water-Tolerant Zinc Hydride Cluster That Reacts Selectively With CO2

Co-reporter:David M. Ermert;Dr. Ion Ghiviriga;Dr. Vincent J. Catalano;Dr. Jason Shearer;Dr. Leslie J. Murray

Angewandte Chemie 2015 Volume 127( Issue 24) pp:7153-7156

Publication Date(Web):

DOI:10.1002/ange.201501539

Abstract

The reaction of [Zn₃Cl₃L], in which L³⁻ is a tris(β-diketiminate) cyclophane, with K(sBu)₃BH afforded [Zn₃(μ-H)₃L] (2), as confirmed by NMR spectroscopy, NOESY, and X-ray crystallography. The complex 2 was air-stable and unreactive towards water, methanol, and other substrates (e.g., nitriles) at room temperature over 24 h but reacted with CO₂ (ca. 1 atm) to generate [Zn₃(μ-H)₂(μ-1,1-O₂CH)] (3). In contrast, [Zn₃(OH)₃L] (4) was found to be unreactive toward CO₂ over the course of several days at 90 °C.

Isolation of a (Dinitrogen)Tricopper(I) Complex

Co-reporter:Leslie J. Murray ; Walter W. Weare ; Jason Shearer ; Alyssa D. Mitchell ;Khalil A. Abboud

Journal of the American Chemical Society 2014 Volume 136(Issue 39) pp:13502-13505

Publication Date(Web):September 19, 2014

DOI:10.1021/ja506445d

Reaction of a tris(β-diketimine) cyclophane, H3L, with benzyl potassium followed by [Cu(OTf)]2(C6H6) affords a tricopper(I) complex containing a bridging dinitrogen ligand. rRaman (νN–N = 1952 cm–1) and 15N NMR (δ = 303.8 ppm) spectroscopy confirm the presence of the dinitrogen ligand. DFT calculations and QTAIM analysis indicate minimal metal-dinitrogen back-bonding with only one molecular orbital of significant N2(2pπ*) and Cu(3dπ)/Cu(3dσ) character (13.6% N, 70.9% Cu). ∇2ρ values for the Cu–N2 bond critical points are analogous to those for polar closed-shell/closed-shell interactions.

Modeling Biological Copper Clusters: Synthesis of a Tricopper Complex, and Its Chloride- and Sulfide-Bridged Congeners

Co-reporter:Gianna N. Di Francesco, Aleth Gaillard, Ion Ghiviriga, Khalil A. Abboud, and Leslie J. Murray

Inorganic Chemistry 2014 Volume 53(Issue 9) pp:4647-4654

Publication Date(Web):April 18, 2014

DOI:10.1021/ic500333p

The synthesis and characterization of a family of tricopper clusters housed within a tris(β-diketimine) cyclophane ligand (H3L) that bear structural similarities to biological copper clusters are reported. In all complexes, each Cu atom is held within the N2-chelate of a single β-diketiminate arm. Reaction of L3– with CuCl affords an anionic complex containing a μ3-chloride donor in the central cavity, whereas there is no evidence for bromide incorporation in the product of the reaction of L3– with CuBr (Cu3L). Cu3L reacts with elemental sulfur to generate the corresponding air-stable mixed-valent (μ3-sulfido)tricopper complex, Cu3(μ3-S)L, which represents the first example of a sulfide-bridged copper cluster in which each metal center is both coordinatively unsaturated and held within a N-rich environment. The calculated LUMO is predominantly Cu–S π* in character and delocalized over all three metal centers, which is consistent with the isotropic ten-line absorption (g ∼ 2.095, A ∼ 33 G) observed at room temperature in EPR spectra of the one-electron chemically reduced complex, [Cu3(μ3-S)L]−.

Preorganized assembly of three iron(II) or manganese(II) β-diketiminate complexes using a cyclophane ligand

Co-reporter:Gary L. Guillet, Forrest T. Sloane, David M. Ermert, Matthew W. Calkins, Marcus K. Peprah, Elisabeth S. Knowles, Erik Čižmár, Khalil A. Abboud, Mark W. Meisel and Leslie J. Murray

Chemical Communications 2013 vol. 49(Issue 59) pp:6635-6637

Publication Date(Web):17 Jun 2013

DOI:10.1039/C3CC43395A

A trinucleating cyclophane bearing three β-diketimine arms, and the corresponding iron(II) and manganese(II) complexes have been synthesized and characterized. The three metal ions are oriented towards the internal void space, and are coordinated by a N2Br2 donor set, in which a unique combination of μ3, μ, and terminal coordination modes are observed for the halide donors.

Synthesis and characterization of a tris(2-hydroxyphenyl)methane-based cryptand and its triiron(III) complex

Co-reporter:Gary L. Guillet, Forrest T. Sloane, Matthieu F. Dumont, Khalil A. Abboud and Leslie J. Murray

Dalton Transactions 2012 vol. 41(Issue 26) pp:7866-7869

Publication Date(Web):04 May 2012

DOI:10.1039/C2DT30312D

Reaction of tris(5-amino-2-ethoxy-3-isopropylphenyl)methane and pyridine-2,6-dicarbonyl-dichloride affords a multi-dentate cryptand in 48% yield. Metallation with iron(III) chloride results in a substantial conformational change of this ligand to give a trianionic triiron(III) complex. Ferric cations line the periphery of the internal cavity with each adopting a square pyramidal N3Cl2 coordination environment.

Insights into small molecule activation by multinuclear first-row transition metal cyclophanates

Co-reporter:David M. Ermert and Leslie J. Murray

Dalton Transactions 2016 - vol. 45(Issue 37) pp:NaN14507-14507

Publication Date(Web):2016/07/21

DOI:10.1039/C6DT01857B

The rational design of trimetallic transition metal clusters supported by a trinucleating cyclophane ligand, L3−, and the reactivities of these complexes with dinitrogen and carbon dioxide are discussed. Emphasis is placed on the differences in the observed reactivity between these trimetallic cyclophane complexes and that of the mono- and dinuclear transition metal compounds.

Synthesis and characterization of a tris(2-hydroxyphenyl)methane-based cryptand and its triiron(III) complex

Co-reporter:Gary L. Guillet, Forrest T. Sloane, Matthieu F. Dumont, Khalil A. Abboud and Leslie J. Murray

Dalton Transactions 2012 - vol. 41(Issue 26) pp:NaN7869-7869

Publication Date(Web):2012/05/04

DOI:10.1039/C2DT30312D

Reaction of tris(5-amino-2-ethoxy-3-isopropylphenyl)methane and pyridine-2,6-dicarbonyl-dichloride affords a multi-dentate cryptand in 48% yield. Metallation with iron(III) chloride results in a substantial conformational change of this ligand to give a trianionic triiron(III) complex. Ferric cations line the periphery of the internal cavity with each adopting a square pyramidal N3Cl2 coordination environment.

A three-coordinate Fe(II) center within a [3Fe–(μ3-S)] cluster that provides an accessible coordination site

Co-reporter:Yousoon Lee, Khalil A. Abboud, Ricardo García-Serres and Leslie J. Murray

Chemical Communications 2016 - vol. 52(Issue 59) pp:NaN9298-9298

Publication Date(Web):2016/07/01

DOI:10.1039/C6CC04671A

A μ3-sulfide bridged triiron cluster(II,II,III) supported by a cyclophane ligand undergoes metal-based reduction to yield an all-ferrous species. The latter complex incorporates a three-coordinate iron center that provides an accessible coordination site to a solvent molecule.

A [3Fe–3S]3+ cluster with exclusively μ-sulfide donors

Co-reporter:Yousoon Lee, Ie-Rang Jeon, Khalil A. Abboud, Ricardo García-Serres, Jason Shearer and Leslie J. Murray

Chemical Communications 2016 - vol. 52(Issue 6) pp:NaN1177-1177

Publication Date(Web):2015/11/25

DOI:10.1039/C5CC07813J

A [3Fe–3(μ-S)]3+ cluster is reported in which each ferric center has a distorted trigonal pyramidal geometry, with an S = 1/2 ground state for the cluster and unusually anisotropic hyperfine coupling constants as determined by variable temperature magnetometry and Mössbauer spectroscopy.

Preorganized assembly of three iron(II) or manganese(II) β-diketiminate complexes using a cyclophane ligand

Co-reporter:Gary L. Guillet, Forrest T. Sloane, David M. Ermert, Matthew W. Calkins, Marcus K. Peprah, Elisabeth S. Knowles, Erik Čižmár, Khalil A. Abboud, Mark W. Meisel and Leslie J. Murray

Chemical Communications 2013 - vol. 49(Issue 59) pp:NaN6637-6637

Publication Date(Web):2013/06/17

DOI:10.1039/C3CC43395A

A trinucleating cyclophane bearing three β-diketimine arms, and the corresponding iron(II) and manganese(II) complexes have been synthesized and characterized. The three metal ions are oriented towards the internal void space, and are coordinated by a N2Br2 donor set, in which a unique combination of μ3, μ, and terminal coordination modes are observed for the halide donors.