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Bhowmik S, Sengupta A, Mukherjee R. Ni(II) and Pd(II) complexes of a new redox-active pentadentate azo-appended 2-aminophenol ligand: Pd(II)-assisted intraligand cyclization forms a phenoxazinyl ring. Dalton Trans 2024; 53:14046-14064. [PMID: 39109537 DOI: 10.1039/d4dt01513d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/21/2024]
Abstract
Square planar complexes of Ni(II) and Pd(II) of a new redox-active pentadentate azo-appended 2-aminophenol ligand (H4L = N,N'-bis(2-hydroxy-3,5-di-tert-butylphenyl)-2,2'-diamino-ortho-azobenzene) in three accessible redox levels [amidophenolate(2-), semiquinonate(1-) π radical, and quinone(0)] were synthesized. The coordinated HL(3-) ligand provides four donor sites [two N(iminophenolates), an N'(azo), and an O(phenolate)], while the phenolic OH group remains free in the three complexes. Cyclic voltammetry on complex [Ni(L)] 1 and its corresponding Pd(II) analogue [Pd(L)] 2 in CH2Cl2 displayed three redox responses (two oxidative at E1/2 = 0.06 V and Epa (anodic peak potential) = 0.80 V and one reductive at -0.77 V for 1 and at E1/2 = 0.08 V and Epa = 0.85 V and at -0.74 V for 2vs. Fc+/Fc). The chemical oxidation of 1 with AgSbF6 afforded [Ni(L)]SbF6·2CH2Cl2 (3·2CH2Cl2). Complex [Pd(L*)] 4, which is coordinated by a phenoxazinyl derivative of L(4-), was obtained via intraligand cyclization in the parent complex 2 under basic oxidizing conditions. The molecular structures of 1, 2, 3·2CH2Cl2 and 4 were elucidated through X-ray crystallography at 100 K. Characterization using 1H NMR, X-band EPR, and UV-VIS-NIR spectroscopy established that the complexes have [NiII{(LISQ)˙2-}] 1, [PdII{(LISQ)˙2-}] 2, [NiII{(LIBQ)-}]SbF6/1+SbF6-(3), and [PdII{(L*AP)˙2-}] 4 electronic states. Complexes 1, 2, and 4 possess paramagnetic St (total spin) = 1/2 ground-state, whereas 3 is diamagnetic (St = 0). Density functional theory (DFT) electronic structural calculations at the B3LYP level rationalized the observed experimental results. Time-dependent (TD)-DFT calculations allowed us to identify the nature of the observed absorption spectra.
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Affiliation(s)
- Saumitra Bhowmik
- Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Arunava Sengupta
- Department of Chemistry and Chemical Biology, Indian Institute of Technology (ISM) Dhanbad, Dhanbad, Jharkhand 826004, India
| | - Rabindranath Mukherjee
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India.
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2
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Carbonel H, Mikulski TD, Nugraha K, Johnston J, Wang Y, Brown SN. Optically active bis(aminophenols) and their metal complexes. Dalton Trans 2023; 52:13290-13303. [PMID: 37668189 DOI: 10.1039/d3dt02436a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/06/2023]
Abstract
Optically active C2-symmetric bis(aminophenols) based on (R)-2,2'-diaminobinaphthyl (BiniqH4) and (R,R)-2,3-butanediyldianthranilate (BdanH4) have been prepared by condensation of the diamines with 3,5-di-tert-butylcatechol. Group 10 bis(iminosemiquinone) complexes (R)-(Biniq)M (M = Pd, Pt) and (C,R,R)-(Bdan)Pd have been prepared by oxidatively metalating the corresponding ligands. In (R)-(Biniq)M, the C2 axis passes through the approximate square plane of the bis(iminosemiquinone)metal core, while in (C,R,R)-(Bdan)Pd the C2 axis is perpendicular to this plane. In the latter compound, the (R,R)-butanediyl strap binds selectively over one enantioface of the metal complex in a conformation where the methyl groups are anti to one another. Osmium oxo complexes with the intrinsically chiral OsO(amidophenoxide)2 chromophore are obtained by metalation of OsO(OCH2CH2O)2 with (R,R)-BdanH4. Both the (A,R,R) and (C,R,R) diastereomers can be observed, with metalation in refluxing toluene selectively giving the latter isomer. The electronic structures of the complexes are illuminated by the circular dichroism spectra, in conjuction with the optical spectra and TDDFT calculations.
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Affiliation(s)
- Halen Carbonel
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
| | - Timothy D Mikulski
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
| | - Kahargyan Nugraha
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
| | - James Johnston
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Yichun Wang
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Seth N Brown
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
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3
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Sailer R, VandeVen W, Teindl K, Chiang L. Ni II and Cu II complexes of a salen ligand bearing ferrocenes in its secondary coordination sphere. RSC Adv 2023; 13:7293-7299. [PMID: 36891492 PMCID: PMC9986886 DOI: 10.1039/d2ra07671c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 02/24/2023] [Indexed: 03/08/2023] Open
Abstract
Herein, we report the synthesis, spectroscopic characterization and electrochemical investigation of the NiII and CuII complexes of a novel Sal ligand bearing two ferrocene moieties attached at its diimine linker, M(Sal)Fc. The electronic spectra of M(Sal)Fc are near identical to its phenyl-substituted counterpart, M(Sal)Ph, indicating the ferrocene moieties exist in the secondary coordination sphere of M(Sal)Fc. The cyclic voltammograms of M(Sal)Fc exhibit an additional two-electron wave in comparison to M(Sal)Ph, which is assigned to the sequential oxidation of the two ferrocene moieties. The chemical oxidation of M(Sal)Fc, monitored by low temperature UV-vis spectroscopy, supports the formation of a mixed valent FeIIFeIII species followed by a bis(ferrocenium) species upon sequential addition of one and two equivalents of chemical oxidant. The addition of a third equivalent of oxidant to Ni(Sal)Fc yielded intense near-IR transitions that are indicative of the formation of a fully delocalized Sal-ligand radical (Sal˙), while the same addition to Cu(Sal)Fc yielded a species that is currently under further spectroscopic investigation. These results suggest the oxidation of the ferrocene moieties of M(Sal)Fc does not affect the electronic structure of the M(Sal) core, and these are thus in the secondary coordination sphere of the overall complex.
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Affiliation(s)
- Rachel Sailer
- Department of Chemistry, University of the Fraser Valley Abbotsford V2S 7M8 British Columbia Canada
| | - Warren VandeVen
- Department of Chemistry, Simon Fraser University Burnaby V5A 1S6 British Columbia Canada
| | - Kaeden Teindl
- Department of Chemistry, University of the Fraser Valley Abbotsford V2S 7M8 British Columbia Canada
| | - Linus Chiang
- Department of Chemistry, University of the Fraser Valley Abbotsford V2S 7M8 British Columbia Canada
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4
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Baryshnikova SV, Poddel’sky AI. Heteroligand Metal Complexes with Extended Redox Properties Based on Redox-Active Chelating Ligands of o-Quinone Type and Ferrocene. Molecules 2022; 27:molecules27123928. [PMID: 35745052 PMCID: PMC9230781 DOI: 10.3390/molecules27123928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 06/13/2022] [Accepted: 06/17/2022] [Indexed: 12/10/2022] Open
Abstract
A combination of different types of redox-active systems in one molecule makes it possible to create coordination compounds with extended redox abilities, combining molecular and electronic structures determined by the features of intra- and intermolecular interactions between such redox-active centres. This review summarizes and analyses information from the literature, published mainly from 2000 to the present, on the methods of preparation, the molecular and electronic structure of mixed-ligand coordination compounds based on redox-active ligands of the o-benzoquinone type and ferrocenes, ferrocene-containing ligands, the features of their redox properties, and some chemical behaviour.
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Wagner HE, Frank N, Barani E, Anson CE, Bayer L, Powell AK, Fink K, Breher F. Asymmetrically Difunctionalized 1,1′‐Ferrocenyl Metalloligands and Their Transition Metal Complexes. Eur J Inorg Chem 2022. [DOI: 10.1002/ejic.202100898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Hanna E. Wagner
- Karlsruhe Institute of Technology (KIT) Institute of Inorganic Chemistry Engesserstraße 15 76131 Karlsruhe Germany
| | - Nils Frank
- Karlsruhe Institute of Technology (KIT) Institute of Nanotechnology Postfach 3630 76021 Karlsruhe Germany
| | - Elham Barani
- Karlsruhe Institute of Technology (KIT) Institute of Nanotechnology Postfach 3630 76021 Karlsruhe Germany
| | - Christopher E. Anson
- Karlsruhe Institute of Technology (KIT) Institute of Inorganic Chemistry Engesserstraße 15 76131 Karlsruhe Germany
| | - Lea Bayer
- Karlsruhe Institute of Technology (KIT) Institute of Inorganic Chemistry Engesserstraße 15 76131 Karlsruhe Germany
| | - Annie K. Powell
- Karlsruhe Institute of Technology (KIT) Institute of Inorganic Chemistry Engesserstraße 15 76131 Karlsruhe Germany
| | - Karin Fink
- Karlsruhe Institute of Technology (KIT) Institute of Nanotechnology Postfach 3630 76021 Karlsruhe Germany
| | - Frank Breher
- Karlsruhe Institute of Technology (KIT) Institute of Inorganic Chemistry Engesserstraße 15 76131 Karlsruhe Germany
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Plajer AJ, Rizzuto FJ, von Krbek LKS, Gisbert Y, Martínez-Agramunt V, Nitschke JR. Oxidation triggers guest dissociation during reorganization of an Fe II 4L 6 twisted parallelogram. Chem Sci 2020; 11:10399-10404. [PMID: 34123180 PMCID: PMC8162311 DOI: 10.1039/d0sc04352d] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2020] [Accepted: 09/09/2020] [Indexed: 12/12/2022] Open
Abstract
A three-dimensional FeII 4L6 parallelogram was prepared from ferrocene-containing ditopic ligands. The steric preference of the bulky ferrocene cores towards meridional vertex coordination brought about this new structure type, in which the ferrocene units adopt three distinct conformations. The structure possesses two distinct, bowl-like cavities that host anionic guests. Oxidation of the ferrocene FeII to ferrocenium FeIII causes rotation of the ferrocene hinges, converting the structure to an FeII 1L1 + species with release of anionic guests, even though the average charge per iron increases in a way that would ordinarily increase guest binding strength. The degrees of freedom exhibited by these new structures - derived from the different configurations of the three ligands surrounding a meridional FeII center and the rotation of ferrocene cores - thus underpin their ability to reconfigure and eject guests upon oxidation.
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Affiliation(s)
- Alex J Plajer
- Department of Chemistry, University of Cambridge Lensfield Rd Cambridge CB2 1EW UK
| | - Felix J Rizzuto
- Department of Chemistry, University of Cambridge Lensfield Rd Cambridge CB2 1EW UK
| | | | - Yohan Gisbert
- Department of Chemistry, University of Cambridge Lensfield Rd Cambridge CB2 1EW UK
| | | | - Jonathan R Nitschke
- Department of Chemistry, University of Cambridge Lensfield Rd Cambridge CB2 1EW UK
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7
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Gianino J, Erickson AN, Markovitz SJ, Brown SN. High-valent osmium iminoxolene complexes. Dalton Trans 2020; 49:8504-8515. [PMID: 32525176 DOI: 10.1039/d0dt01735c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
2-(Arylamino)-4,6-di-tert-butylphenols containing 4-substituted phenyl groups (RapH2) react with oxobis(ethylene glycolato)osmium(vi) in acetone to give square pyramidal bis(amidophenoxide)oxoosmium(vi) complexes. A mono-amidophenoxide complex is observed as an intermediate in these reactions. Reactions in dichloromethane yield the diolate (Hap)2Os(OCH2CH2O). Both the glycolate and oxo complex are converted to the corresponding cis-dichloride complex on treatment with chlorotrimethylsilane. The novel bis(aminophenol) ligand EganH4, containing an ethylene glycol dianthranilate bridge, forms the chelated bis(amidophenoxide) complex (Egan)OsO, where the two nitrogen atoms of the tetradentate ligand bind in the trans positions of the square pyramid. Structural and spectroscopic features of the complexes are described well by an osmium(vi)-amidophenoxide formulation, with the amount of π donation from ligand to metal increasing markedly as the co-ligands change from oxo to diolate to dichloride. In the oxo-bis(amidophenoxides), the symmetry of the ligand π orbitals results in only one effective π donor interaction, splitting the energy of the two osmium-oxo π* orbitals and rendering the osmium-oxo bonding appreciably anisotropic.
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Affiliation(s)
- Jacqueline Gianino
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
| | - Alexander N Erickson
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
| | - Sean J Markovitz
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
| | - Seth N Brown
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
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8
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Gianino J, Brown SN. Highly covalent metal-ligand π bonding in chelated bis- and tris(iminoxolene) complexes of osmium and ruthenium. Dalton Trans 2020; 49:7015-7027. [PMID: 32367103 DOI: 10.1039/d0dt01287d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The bis(aminophenol) 2,2'-biphenylbis(3,5-di-tert-butyl-2-hydroxyphenylamine) (ClipH4) forms trans-(Clip)Os(py)2 upon aerobic reaction of the ligand with {(p-cymene)OsCl2}2 in the presence of pyridine and triethylamine. A more oxidized species, cis-β-(Clip)Os(OCH2CH2O), is formed from reaction of the ligand with the osmium(vi) complex OsO(OCH2CH2O)2, and reacts with Me3SiCl to give the chloro complex cis-β-(Clip)OsCl2. Octahedral osmium and ruthenium tris-iminoxolene complexes are formed from the chelating ligand tris(2-(3',5'-di-tert-butyl-2'-hydroxyphenyl)amino-4-methylphenyl)amine (MeClampH6) on aerobic reaction with divalent metal precursors. The complexes' structural and electronic features are well described using a simple bonding model that emphasizes the covalency of the π bonding between the metal and iminoxolene ligands rather than attempting to dissect the parts into discrete oxidation states. Emphasizing the continuity of bonding between disparate complexes, the structural data from a variety of Os and Ru complexes show good correlations to π bond order, and the response of the intraligand bond distances to the bond order can be analyzed to illuminate the polarity of the bonding between metal and the redox-active orbital on the iminoxolenes. The osmium compounds'π bonding orbitals are about 40% metal-centered and 60% ligand-centered, with the ruthenium compounds' orbitals about 65% metal-centered and 35% ligand-centered.
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Affiliation(s)
- Jacqueline Gianino
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
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9
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Do TH, Brown SN. Mono- and bimetallic pentacoordinate silicon complexes of a chelating bis(catecholimine) ligand. Dalton Trans 2019; 48:11565-11574. [PMID: 31297499 DOI: 10.1039/c9dt02475a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Schiff base condensation of 4,5-diamino-9,9-dimethylxanthene with 4,6-di-tert-butylcatechol-3-carboxaldehyde affords the bis(catecholimine) ligand XbicH4, which can bind metals in both a square bis(catecholate) upper pocket and a pentagonal N2O3 lower pocket. Metalation with PhSiCl3 results in [(XbicH2)SiPh][HCl2], where the silicon adopts a five-coordinate, square pyramidal geometry in the upper pocket and the lower pocket binds to two protons on the imine nitrogens. Deprotonation of the imines with LiOtBu, NaN[SiMe3]2, or AgOAc results in binding of the univalent metal ion in the lower pocket, where it adopts an unusual pentagonal monopyramidal geometry in the solid state. The complexes show irreversible electrochemistry, with oxidations taking place at relatively high potentials.
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Affiliation(s)
- Thomas H Do
- Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, IN 46556-5670, USA.
| | - Seth N Brown
- Department of Chemistry and Biochemistry, University of Notre Dame, 251 Nieuwland Science Hall, Notre Dame, IN 46556-5670, USA.
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10
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Rajput A, Sharma AK, Barman SK, Lloret F, Mukherjee R. Six-coordinate [Co III(L) 2] z (z = 1-, 0, 1+) complexes of an azo-appended o-aminophenolate in amidate(2-) and iminosemiquinonate π-radical (1-) redox-levels: the existence of valence-tautomerism. Dalton Trans 2018; 47:17086-17101. [PMID: 30465680 DOI: 10.1039/c8dt03257b] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Aerobic reaction of the ligand H2L1, 2-(2-phenylazo)-anilino-4,6-di-tert-butylphenol, CoCl2·6H2O and Et3N in MeOH under refluxing conditions produces, after work-up and recrystallization, black crystals of [Co(L1)2] (1). When examined by cyclic voltammetry, 1 displays in CH2Cl2 three one-electron redox responses: two oxidative, E11/2 = 0.30 V (peak-to-peak separation, ΔEp = 100 mV) and E21/2 = 1.04 V (ΔEp = 120 mV), and one reductive E1/2 = -0.27 V (ΔEp = 120 mV) vs. SCE. Consequently, 1 is chemically oxidized by 1 equiv. of [FeIII(η5-C5H5)2][PF6], affording the isolation of deep purple crystals of [Co(L1)2][PF6]·2CH2Cl2 (2), and one-electron reduction with [CoII(η5-C5H5)2] yielded bluish-black crystals of [CoIII(η5-C5H5)2][Co(L1)2]·MeCN (3). A solid sample of 1 exhibits temperature-independent (50-300 K) magnetism, revealing the presence of a free radical (S = 1/2), which exhibits an isotropic EPR signal (g = 2.003) at 298 K and at 77 K an eight-line feature characteristic of hyperfine-interaction of the radical with the Co (I = 7/2) nucleus. Based on X-ray structural parameters of 1-3 at 100 K, magnetic and EPR spectral behaviour of 1, and variable-temperature (233-313 K) 1H NMR spectral features of 1-3 and 13C NMR spectra at 298 K of 2 and 3 in CDCl3 point to the electronic structure of the complexes as either [CoIII{(LAP)2-}{(LISQ)}˙-] or [CoIII{(L1)2}˙3-] (delocalized nature favours the latter description) (1), [CoIII{(LISQ)˙-}2][PF6]·2CH2Cl2 (2) and [CoIII(η5-C5H5)2][CoIII{(LAP)2-}2]·MeCN (3) [(LAP)2- and (LISQ)˙- represent the redox-level of coordinated ligands o-amidophenolate(2-) ion and o-iminobenzosemiquinonate(1-) π-radical ion, respectively]. Notably, all the observed redox processes are ligand-centred. To the best of our knowledge, this is the first time that six-coordinate complexes of a common tridentate o-aminophenolate-based ligand have been structurally characterized for the parent 1, its monocation 2 and the monoanion 3 counterparts. Temperature-dependent 1H NMR spectra reveal the existence of valence-tautomeric equilibria in 1-3. Density Functional Theory (DFT) calculations at the B3LYP-level of theory corroborate the electronic structural assignment of 1-3 from experimental data. The origins of the observed UV-VIS-NIR absorptions for 1-3 have been assigned, based on time-dependent (TD)-DFT calculations.
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Affiliation(s)
- Amit Rajput
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208 016, India.
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Conner KM, Arostegui AC, Swanson DD, Brown SN. When Do Strongly Coupled Diradicals Show Strongly Coupled Reactivity? Thermodynamics and Kinetics of Hydrogen Atom Transfer Reactions of Palladium and Platinum Bis(iminosemiquinone) Complexes. Inorg Chem 2018. [PMID: 29517233 DOI: 10.1021/acs.inorgchem.8b00068] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The 2,2'-biphenylene-bridged bis(iminosemiquinone) complexes ( tBuClip)M [ tBuClipH4 = 4,4'-di- tert-butyl- N, N'-bis(3,5-di- tert-butyl-2-hydroxyphenyl)-2,2'-diaminobiphenyl; M = Pd, Pt] can be reduced to the bis(aminophenoxide) complexes ( tBuClipH2)M by reaction with hydrazobenzene (M = Pd) or by catalytic hydrogenation (M = Pt). The palladium complex with one aminophenoxide ligand and one iminosemiquinone ligand, ( tBuClipH)Pd, is generated by comproportionation of ( tBuClip)Pd with ( tBuClipH2)Pd in a process that is both slow (0.06 M-1 s-1 in toluene at 23 °C) and only modestly favorable ( Kcom = 1.9 in CDCl3), indicating that both N-H bonds have essentially the same bond strength. The mono(iminoquinone) complex ( tBuClipH)Pt has not been observed, indicating that the platinum analogue shows no tendency to comproportionate ( Kcom < 0.1). The average bond dissociation free energies (BDFE) of the complexes have been established by equilibration with suitably substituted hydrazobenzenes, and the palladium bis(iminosemiquinone) is markedly more oxidizing than the platinum compound, with hydrogen transfer from ( tBuClipH2)Pt to ( tBuClip)Pd occurring with Δ G° = -8.9 kcal mol-1. The palladium complex ( tBuClipH2)Pd reacts with nitroxyl radicals in two observable steps, with the first hydrogen transfer taking place slightly faster than the second. In the platinum analogue, the first hydrogen transfer is much slower than the second, presumably because the N-H bond in the monoradical complex ( tBuClipH)Pt is unusually weak. Using driving force-rate correlations, it is estimated that this bond has a BDFE of 55.1 kcal mol-1, which is 7.1 kcal mol-1 weaker than that of the first N-H bond in ( tBuClipH2)Pt. The two radical centers in the platinum, but not the palladium, complex thus act in concert with each other and display a strong thermodynamic bias toward two-electron reactivity. The greater thermodynamic and kinetic coupling in the platinum complex is attributed to the stronger metal-ligand π interactions in this compound.
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Affiliation(s)
- Kyle M Conner
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46556-5670 , United States
| | - AnnaMaria C Arostegui
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46556-5670 , United States
| | - Daniel D Swanson
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46556-5670 , United States
| | - Seth N Brown
- Department of Chemistry and Biochemistry , University of Notre Dame , 251 Nieuwland Science Hall , Notre Dame , Indiana 46556-5670 , United States
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12
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Conner KM, Perugini AL, Malabute M, Brown SN. Group 10 Bis(iminosemiquinone) Complexes: Measurement of Singlet–Triplet Gaps and Analysis of the Effects of Metal and Geometry on Electronic Structure. Inorg Chem 2018; 57:3272-3286. [DOI: 10.1021/acs.inorgchem.8b00062] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Kyle M. Conner
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556-5670, United States
| | - Amanda L. Perugini
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556-5670, United States
| | - Miko Malabute
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556-5670, United States
| | - Seth N. Brown
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, Indiana 46556-5670, United States
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