51
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Wang Z, Jagličić Z, Han LL, Zhuang GL, Luo GG, Zeng SY, Tung CH, Sun D. Octanuclear Ni(ii) cubes based on halogen-substituted pyrazolates: synthesis, structure, electrochemistry and magnetism. CrystEngComm 2016. [DOI: 10.1039/c6ce00528d] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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52
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Broere DLJ, Plessius R, van der Vlugt JI. New avenues for ligand-mediated processes--expanding metal reactivity by the use of redox-active catechol, o-aminophenol and o-phenylenediamine ligands. Chem Soc Rev 2015; 44:6886-915. [PMID: 26148803 DOI: 10.1039/c5cs00161g] [Citation(s) in RCA: 329] [Impact Index Per Article: 36.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Redox-active ligands have evolved from being considered spectroscopic curiosities - creating ambiguity about formal oxidation states in metal complexes - to versatile and useful tools to expand on the reactivity of (transition) metals or to even go beyond what is generally perceived possible. This review focusses on metal complexes containing either catechol, o-aminophenol or o-phenylenediamine type ligands. These ligands have opened up a new area of chemistry for metals across the periodic table. The portfolio of ligand-based reactivity invoked by these redox-active entities will be discussed. This ranges from facilitating oxidative additions upon d(0) metals or cross coupling reactions with cobalt(iii) without metal oxidation state changes - by functioning as an electron reservoir - to intramolecular ligand-to-substrate single-electron transfer to create a reactive substrate-centered radical on a Pd(ii) platform. Although the current state-of-art research primarily consists of stoichiometric and exploratory reactions, several notable reports of catalysis facilitated by the redox-activity of the ligand will also be discussed. In conclusion, redox-active ligands containing catechol, o-aminophenol or o-phenylenediamine moieties show great potential to be exploited as reversible electron reservoirs, donating or accepting electrons to activate substrates and metal centers and to enable new reactivity with both early and late transition as well as main group metals.
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Affiliation(s)
- Daniël L J Broere
- University of Amsterdam, van't Hoff Institute for Molecular Sciences, Homogeneous, Bio-Inspired and Supramolecular Catalysis Group, Science Park 904, Amsterdam, the Netherlands
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53
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Poitras AM, Bogart JA, Cole BE, Carroll PJ, Schelter EJ, Graves CR. Synthesis and Characterization of Aluminum Complexes of Redox-Active Pyridyl Nitroxide Ligands. Inorg Chem 2015; 54:10901-8. [DOI: 10.1021/acs.inorgchem.5b01941] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andrew M. Poitras
- Department of Chemistry & Biochemistry, Albright College, 13th & Bern Streets, Reading, Pennsylvania 19612, United States
| | - Justin A. Bogart
- P. Roy, Diana T. Vagelos Laboratories,
Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United States
| | - Bren E. Cole
- P. Roy, Diana T. Vagelos Laboratories,
Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United States
| | - Patrick J. Carroll
- P. Roy, Diana T. Vagelos Laboratories,
Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United States
| | - Eric J. Schelter
- P. Roy, Diana T. Vagelos Laboratories,
Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United States
| | - Christopher R. Graves
- Department of Chemistry & Biochemistry, Albright College, 13th & Bern Streets, Reading, Pennsylvania 19612, United States
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54
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Damon PL, Liss CJ, Lewis RA, Morochnik S, Szpunar DE, Telser J, Hayton TW. Quantifying the Electron Donor and Acceptor Abilities of the Ketimide Ligands in M(N═C(t)Bu2)4 (M = V, Nb, Ta). Inorg Chem 2015; 54:10081-95. [PMID: 26419513 PMCID: PMC4659433 DOI: 10.1021/acs.inorgchem.5b02017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Addition of 4 equiv of Li(N═C(t)Bu2) to VCl3 in THF, followed by addition of 0.5 equiv of I2, generates the homoleptic V(IV) ketimide complex, V(N═C(t)Bu2)4 (1), in 42% yield. Similarly, reaction of 4 equiv of Li(N═C(t)Bu2) with NbCl4(THF)2 in THF affords the homoleptic Nb(IV) ketimide complex, Nb(N═C(t)Bu2)4 (2), in 55% yield. Seeking to extend the series to the tantalum congener, a new Ta(IV) starting material, TaCl4(TMEDA) (3), was prepared via reduction of TaCl5 with Et3SiH, followed by addition of TMEDA. Reaction of 3 with 4 equiv of Li(N═C(t)Bu2) in THF results in the isolation of a Ta(V) ketimide complex, Ta(Cl)(N═C(t)Bu2)4 (5), which can be isolated in 32% yield. Reaction of 5 with Tl(OTf) yields Ta(OTf)(N═C(t)Bu2)4 (6) in 44% yield. Subsequent reduction of 6 with Cp*2Co in toluene generates the homoleptic Ta(IV) congener Ta(N═C(t)Bu2)4 (7), although the yields are poor. All three homoleptic group 5 ketimide complexes exhibit squashed tetrahedral geometries in the solid state, as determined by X-ray crystallography. This geometry leads to a d(x(2)-y(2))(1) ((2)B1 in D(2d)) ground state, as supported by DFT calculations. EPR spectroscopic analysis of 1 and 2, performed at X- and Q-band frequencies (∼9 and 35 GHz, respectively), further supports the (2)B1 ground-state assignment, whereas comparison of 1, 2, and 7 with related group 5 tetra(aryl), tetra(amido), and tetra(alkoxo) complexes shows a higher M-L covalency in the ketimide-metal interaction. In addition, a ligand field analysis of 1 and 2 demonstrates that the ketimide ligand is both a strong π-donor and strong π-acceptor, an unusual combination found in very few organometallic ligands.
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Affiliation(s)
- Peter L. Damon
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
| | - Cameron J. Liss
- Department of Biological, Chemical and Physical Sciences, Roosevelt University, 430 S. Michigan Ave. Chicago, Illinois 60605-1394 United States
| | - Richard A. Lewis
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
| | - Simona Morochnik
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
| | - David E. Szpunar
- Department of Biological, Chemical and Physical Sciences, Roosevelt University, 430 S. Michigan Ave. Chicago, Illinois 60605-1394 United States
| | - Joshua Telser
- Department of Biological, Chemical and Physical Sciences, Roosevelt University, 430 S. Michigan Ave. Chicago, Illinois 60605-1394 United States
| | - Trevor W. Hayton
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States
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55
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Heins SP, Morris WD, Wolczanski PT, Lobkovsky EB, Cundari TR. Nitrene Insertion into CC and CH Bonds of Diamide Diimine Ligands Ligated to Chromium and Iron. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201507463] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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56
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Heins SP, Morris WD, Wolczanski PT, Lobkovsky EB, Cundari TR. Nitrene Insertion into CC and CH Bonds of Diamide Diimine Ligands Ligated to Chromium and Iron. Angew Chem Int Ed Engl 2015; 54:14407-11. [DOI: 10.1002/anie.201507463] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Indexed: 11/11/2022]
Affiliation(s)
- Spencer P. Heins
- Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14850 (USA)
| | - Wesley D. Morris
- Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14850 (USA)
| | - Peter T. Wolczanski
- Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14850 (USA)
| | - Emil B. Lobkovsky
- Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, NY 14850 (USA)
| | - Thomas R. Cundari
- Department of Chemistry, Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Box 305070, Denton, TX 76203‐5070 (USA)
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57
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Wang D, Lindeman SV, Fiedler AT. Bimetallic Complexes Supported by a Redox-Active Ligand with Fused Pincer-Type Coordination Sites. Inorg Chem 2015; 54:8744-54. [PMID: 26280846 DOI: 10.1021/acs.inorgchem.5b01380] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The remarkable chemistry of mononuclear complexes featuring tridentate, meridionally chelating "pincer" ligands has stimulated the development of ligand frameworks containing multiple pincer sites. Here, the coordination chemistry of a novel pentadentate ligand (L(N3O2)) that provides two closely spaced NNO pincer-type compartments fused together at a central diarylamido unit is described. The trianionic L(N3O2) chelate supports homobimetallic structures in which each M(II) ion (M = Co, Cu, Zn) is bound in a meridional fashion by the bridging diarylamido N atom and O,N-donors of the salicyaldimine arms. The metal centers are also coordinated by a mono- or bidentate auxiliary ligand (L(aux)), resulting in complexes with the general form [M2(L(N3O2))(L(aux))2](+) (where L(aux) = 1-methyl-benzimidazole (1MeBI), 2,2'-bipyridine (bpy), 4,4'-dibromo-2,2'-bipyridine (bpy(Br2)), or (S)-2-(4-isopropyl-4,5-dihydrooxazolyl)pyridine (S-(iPr)OxPy)). The fused nature of the NNO pincer sites results in short metal-metal distances ranging from 2.70 Å for [Co2(L(N3O2)) (bpy)2](+) to 3.28 Å for [Zn2(L(N3O2)) (bpy)2](+), as revealed by X-ray crystallography. The complexes possess C2 symmetry due to the twisting of the aryl rings of the μ-NAr2 core; spectroscopic studies indicate that chiral L(aux) ligands, such as S-(iPr)OxPy, are capable of controlling the helical sense of the L(N3O2) scaffold. Since the four- or five-coordinate M(II) centers are linked solely by the amido moiety, each features an open coordination site in the intermetallic region, allowing for the possibility of metal-metal cooperativity in small-molecule activation. Indeed, the dicobalt(II) complex [Co2(L(N3O2)) (bpy(Br2))2](+) reacts with O2 to yield a dicobalt(III) species with a μ-1,2-peroxo ligand. The bpy-containing complexes exhibit rich electrochemical properties due to multiple metal- and ligand-based redox events across a wide (3.0 V) potential window. Using electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT), it was determined that one-electron oxidation of [Co2(L(N3O2)) (bpy)2](+) results in formation of a S = 1/2 species with a L(N3O2)-based radical coupled to low-spin Co(II) centers.
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Affiliation(s)
- Denan Wang
- Department of Chemistry, Marquette University , Milwaukee, Wisconsin 53201, United States
| | - Sergey V Lindeman
- Department of Chemistry, Marquette University , Milwaukee, Wisconsin 53201, United States
| | - Adam T Fiedler
- Department of Chemistry, Marquette University , Milwaukee, Wisconsin 53201, United States
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58
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Lindley BM, Wolczanski PT, Cundari TR, Lobkovsky EB. First-Row Transition Metal and Lithium Pyridine-ene-amide Complexes Exhibiting N- and C-Isomers and Ligand-Based Activation of Benzylic C–H Bonds. Organometallics 2015. [DOI: 10.1021/acs.organomet.5b00385] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Brian M. Lindley
- Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Peter T. Wolczanski
- Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Thomas R. Cundari
- Department of Chemistry, Center for Advanced
Scientific Computing and Modeling (CASCaM), University of North Texas, Box 305070, Denton, Texas 76203-5070, United States
| | - Emil B. Lobkovsky
- Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
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59
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VenkatRamani S, Huff NB, Jan MT, Ghiviriga I, Abboud KA, Veige AS. New Alkylidyne Complexes Featuring a Flexible Trianionic ONO3– Pincer-Type Ligand: Inorganic Enamine Effect versus Sterics in Electrophilic Additions. Organometallics 2015. [DOI: 10.1021/acs.organomet.5b00155] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sudarsan VenkatRamani
- Department of Chemistry,
Center for Catalysis, University of Florida, Gainesville, Florida 32611, United States
| | - Nicholas B. Huff
- Department of Chemistry,
Center for Catalysis, University of Florida, Gainesville, Florida 32611, United States
| | - Muhammad Tariq Jan
- Department of Chemistry,
Center for Catalysis, University of Florida, Gainesville, Florida 32611, United States
| | - Ion Ghiviriga
- Department of Chemistry,
Center for Catalysis, University of Florida, Gainesville, Florida 32611, United States
| | - Khalil A. Abboud
- Department of Chemistry,
Center for Catalysis, University of Florida, Gainesville, Florida 32611, United States
| | - Adam S. Veige
- Department of Chemistry,
Center for Catalysis, University of Florida, Gainesville, Florida 32611, United States
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60
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Hewage JS, Wanniarachchi S, Morin TJ, Liddle BJ, Banaszynski M, Lindeman SV, Bennett B, Gardinier JR. Homoleptic nickel(II) complexes of redox-tunable pincer-type ligands. Inorg Chem 2014; 53:10070-84. [PMID: 25222027 PMCID: PMC5047063 DOI: 10.1021/ic500657e] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Different synthetic methods have been developed to prepare eight new redox-active pincer-type ligands, H(X,Y), that have pyrazol-1-yl flanking donors attached to an ortho-position of each ring of a diarylamine anchor and that have different groups, X and Y, at the para-aryl positions. Together with four previously known H(X,Y) ligands, a series of 12 Ni(X,Y)2 complexes were prepared in high yields by a simple one-pot reaction. Six of the 12 derivatives were characterized by single-crystal X-ray diffraction, which showed tetragonally distorted hexacoordinate nickel(II) centers. The nickel(II) complexes exhibit two quasi-reversible one-electron oxidation waves in their cyclic voltammograms, with half-wave potentials that varied over a remarkable 700 mV range with the average of the Hammett σ(p) parameters of the para-aryl X, Y groups. The one- and two-electron oxidized derivatives [Ni(Me,Me)2](BF4)n (n = 1, 2) were prepared synthetically, were characterized by X-band EPR, electronic spectroscopy, and single-crystal X-ray diffraction (for n = 2), and were studied computationally by DFT methods. The dioxidized complex, [Ni(Me,Me)2](BF4)2, is an S = 2 species, with nickel(II) bound to two ligand radicals. The mono-oxidized complex [Ni(Me,Me)2](BF4), prepared by comproportionation, is best described as nickel(II) with one ligand centered radical. Neither the mono- nor the dioxidized derivative shows any substantial electronic coupling between the metal and their bound ligand radicals because of the orthogonal nature of their magnetic orbitals. On the other hand, weak electronic communication occurs between ligands in the mono-oxidized complex as evident from the intervalence charge transfer (IVCT) transition found in the near-IR absorption spectrum. Band shape analysis of the IVCT transition allowed comparisons of the strength of the electronic interaction with that in the related, previously known, Robin-Day class II mixed valence complex, [Ga(Me,Me)2](2+).
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Affiliation(s)
- Jeewantha S. Hewage
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Sarath Wanniarachchi
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Tyler J. Morin
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Brendan J. Liddle
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Megan Banaszynski
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Sergey V. Lindeman
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
| | - Brian Bennett
- Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, United States
| | - James R. Gardinier
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
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61
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O'Reilly ME, Veige AS. Trianionic pincer and pincer-type metal complexes and catalysts. Chem Soc Rev 2014; 43:6325-69. [DOI: 10.1039/c4cs00111g] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This review provides a comprehensive examination of the synthesis, characterization, properties, and catalytic applications of trianionic pincer metal complexes.
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Affiliation(s)
| | - Adam S. Veige
- Center for Catalysis
- University of Florida
- Gainesville, USA
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62
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Sazama GT, Betley TA. Multiple, disparate redox pathways exhibited by a tris(pyrrolido)ethane iron complex. Inorg Chem 2013; 53:269-81. [PMID: 24320208 DOI: 10.1021/ic402210j] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Iron(III) complexes of the tris(pyrrolide)ethane trianion have been synthesized by reaction of one- and two-electron oxidants with [(tpe)Fe(THF)][Li(THF)4] (tpe = tris(5-mesitylpyrrolyl)ethane). X-ray crystallography, (57)Fe Mössbauer, (1)H NMR and EPR spectroscopy, SQUID magnetometry, and density functional theory calculations were employed to rigorously establish the iron 3+ oxidation state. All oxidants employed are proposed to operate via an inner-sphere electron transfer mechanism. Dialkyl peroxides and dibenzyldisulfide served to oxidize iron by one electron, and group transfer of an aryl nitrene unit to the Fe(2+) starting material resulted in formation of Fe(3+) amido species following H-atom abstraction by a presumed nitrenoid intermediate. Single electron transfer to and from diphenyldiazoalkane was also observed to yield a diphenyldiazomethanyl radical anion antiferromagnetically coupled to the S = 5/2 Fe(3+). Isolation of Fe(3+) complexes of tpe, in comparison with previous results wherein the tpe ligand was the redox active moiety, presents an unusual juxtaposition of two noncommunicating redox reservoirs, each accessible via different reaction pathways (namely, inner- and outer-sphere electron transfer).
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Affiliation(s)
- Graham T Sazama
- Department of Chemistry and Chemical Biology, Harvard University , 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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