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Montgomery CL, Amtawong J, Jordan AM, Kurtz DA, Dempsey JL. Proton transfer kinetics of transition metal hydride complexes and implications for fuel-forming reactions. Chem Soc Rev 2023; 52:7137-7169. [PMID: 37750006 DOI: 10.1039/d3cs00355h] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Proton transfer reactions involving transition metal hydride complexes are prevalent in a number of catalytic fuel-forming reactions, where the proton transfer kinetics to or from the metal center can have significant impacts on the efficiency, selectivity, and stability associated with the catalytic cycle. This review correlates the often slow proton transfer rate constants of transition metal hydride complexes to their electronic and structural descriptors and provides perspective on how to exploit these parameters to control proton transfer kinetics to and from the metal center. A toolbox of techniques for experimental determination of proton transfer rate constants is discussed, and case studies where proton transfer rate constant determination informs fuel-forming reactions are highlighted. Opportunities for extending proton transfer kinetic measurements to additional systems are presented, and the importance of synergizing the thermodynamics and kinetics of proton transfer involving transition metal hydride complexes is emphasized.
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Affiliation(s)
- Charlotte L Montgomery
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Jaruwan Amtawong
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Aldo M Jordan
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Daniel A Kurtz
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
| | - Jillian L Dempsey
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, 27599-3290, USA.
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2
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Panigrahi D, Mondal M, Gupta R, Mani G. Four- and five-coordinate nickel(ii) complexes bearing new diphosphine-phosphonite and triphosphine-phosphite ligands: catalysts for N-alkylation of amines. RSC Adv 2022; 12:4510-4520. [PMID: 35425522 PMCID: PMC8981024 DOI: 10.1039/d1ra08961g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 12/12/2021] [Indexed: 11/21/2022] Open
Abstract
The reaction of Ph2PCH2OH with PhPCl2 and PCl3 in the presence of Et3N afforded new phosphonite compounds PhP(OCH2PPh2)21 and P(OCH2PPh2)32, respectively. The reaction between 1 and [NiCl2(DME)] in dichloromethane gave the five-coordinate complex [NiCl2(1-κ3 P,P,P)] 3. Conversely, 1 reacts with [NiCl2(DME)] in the presence of NH4PF6 in dichloromethane to yield the four coordinate ionic complex [NiCl(1-κ3 P,P,P)][PF6] 4. The reactions between 1, [NiCl2(DME)] and KPF6 in the presence of RNC (R = Xylyl, t Bu and iPr) in dichloromethane yielded the five coordinate monocationic [NiCl(1-κ3 P,P,P)(RNC)][PF6] (R = Xylyl) and dicationic [Ni(1-κ3 P,P,P)(RNC)2][PF6]2 (R = t Bu and iPr) complexes, respectively. The analogous reaction of 2 with [NiCl2(DME)] in the presence of KPF6 gave complex [NiCl(2-κ4 P,P,P,P)][PF6], 8. The structures of all complexes were determined by single crystal X-ray diffraction studies and supported by spectroscopic methods. To demonstrate their catalytic application, N-alkylation reactions between primary aryl amines, benzyl and 4-methoxy benzyl alcohols were found to proceed smoothly in the presence of 2.5 mol% of complexes bearing ligand 1 and <0.5 mmol of KOBu t in toluene at 140 °C. The C-N coupled products were formed in very good yields. Its substrate scope includes sterically encumbered, heterocyclic amines and aliphatic alcohol.
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Affiliation(s)
- Dipankar Panigrahi
- Department of Chemistry, Indian Institute of Technology Kharagpur Kharagpur 721 302 India +91 3222 282252 +91 3222 282320
| | - Munmun Mondal
- Department of Chemistry, Indian Institute of Technology Kharagpur Kharagpur 721 302 India +91 3222 282252 +91 3222 282320
| | - Rohit Gupta
- Department of Chemistry, Indian Institute of Technology Kharagpur Kharagpur 721 302 India +91 3222 282252 +91 3222 282320
| | - Ganesan Mani
- Department of Chemistry, Indian Institute of Technology Kharagpur Kharagpur 721 302 India +91 3222 282252 +91 3222 282320
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3
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Pal N, Naskar T, Majumdar A. Synthesis, structural diversity and redox reactions in 1, 2- Bis(diphenylphopshinoethane)Nickel(II)-Thiolate complexes. Inorganica Chim Acta 2022. [DOI: 10.1016/j.ica.2021.120738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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4
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Murueta‐Cruz BA, Berlanga‐Vázquez A, Martínez‐Otero D, Benitez LN, Castillo I, Mondragón‐Díaz A. Planar or Bent? Redox Modulation of Hydrogenase Bimetallic Models by the [Ni
2
(μ‐SAr)
2
] Core Conformation. Eur J Inorg Chem 2021. [DOI: 10.1002/ejic.202100105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Brenda A. Murueta‐Cruz
- Departamento de Química Facultad de Ciencias Universidad del Valle Ciudad Universitaria Meléndez Calle 13 # 100-00 Cali Colombia
| | - Armando Berlanga‐Vázquez
- Instituto de Química Universidad Nacional Autónoma de México Ciudad Universitaria 04510 Ciudad de México México
| | - Diego Martínez‐Otero
- Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM Carretera Toluca-Atlacomulco km 14.5 Toluca 50200 Estado de México México
| | - Luis Norberto Benitez
- Departamento de Química Facultad de Ciencias Universidad del Valle Ciudad Universitaria Meléndez Calle 13 # 100-00 Cali Colombia
| | - Ivan Castillo
- Instituto de Química Universidad Nacional Autónoma de México Ciudad Universitaria 04510 Ciudad de México México
| | - Alexander Mondragón‐Díaz
- Departamento de Química Facultad de Ciencias Universidad del Valle Ciudad Universitaria Meléndez Calle 13 # 100-00 Cali Colombia
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5
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Das A, Ganguly T, Majumdar A. Thiolate Coordination vs C-S Bond Cleavage of Thiolates in Dinickel(II) Complexes. Inorg Chem 2021; 60:944-958. [PMID: 33405907 DOI: 10.1021/acs.inorgchem.0c03068] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A detailed study for the synthesis of dinickel(II)-thiolate and dinickel(II)-hydrosulfide complexes and the complete characterization of the relevant intermediates involved in the C-S bond cleavage of thiolates are presented. Hydrated Ni(II) salts mediate the hydrolytic C-S bond cleavage of thiolates (NaSR/RSH; R = Me, Et, nBu, tBu), albeit inefficiently, to yield a mixture of a dinickel(II)-hydrosulfide complex, [Ni2(BPMP)(μ-SH)(DMF)2]2+ (1), and the corresponding dinickel(II)-thiolate complexes, such as [Ni2(BPMP)(μ-SEt)(ClO4)]1+ (2) (HBPMP is 2,6-bis[[bis(2-pyridylmethyl)amino]methyl]-4-methylphenol). A systematic study for the reactivity of thiolates with Ni(II) was therefore pursued which finally yielded 1 as a pure product which has been characterized in comparison with the dinickel(II)-dichloride complex, [Ni2(BPMP)(Cl)2(MeOH)2]1+ (3). While the reaction of thiolates with anhydrous Ni(OTf)2 in dry conditions could only yield [Ni2(BPMP)(OTf)2]1+ (5) instead of the expected dinickel(II)-thiolate compound, the C-S bond cleavage could be suppressed by the use of a chelating thiol, such as PhCOSH, to yield [Ni2(BPMP)(SCOPh)2]1+ (6). Finally, with the suitable choice of a monodentate thiol, a dinickel(II)-monothiolate complex, [Ni2(BPMP)(SPh)(DMF)(MeOH)(H2O)]2+ (7), was isolated as a pure product within 1 h of reaction, which after a longer time of reaction yielded 1 and PhOH. Complex 7 may thus be regarded as the intermediate that precedes the C-S bond cleavage and is generated by the reaction of a thiolate with an initially formed dinickel(II)-solvento complex, [Ni2(BPMP)(MeOH)2(H2O)2]3+(4). Selected dinickel(II) complexes were explored further for the scope of substitution reactions, and the results include the isolation of a dinickel(II)-bis(thiolate) complex, [Ni2(BPMP)(μ-SPh)2]1+ (8).
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Affiliation(s)
- Ayan Das
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata 700032, India
| | - Tuhin Ganguly
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata 700032, India
| | - Amit Majumdar
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata 700032, India
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6
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Vansuch GE, Wu CH, Haja DK, Blair SA, Chica B, Johnson MK, Adams MWW, Dyer RB. Metal-ligand cooperativity in the soluble hydrogenase-1 from Pyrococcus furiosus. Chem Sci 2020; 11:8572-8581. [PMID: 34123117 PMCID: PMC8163435 DOI: 10.1039/d0sc00628a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Metal–ligand cooperativity is an essential feature of bioinorganic catalysis. The design principles of such cooperativity in metalloenzymes are underexplored, but are critical to understand for developing efficient catalysts designed with earth abundant metals for small molecule activation. The simple substrate requirements of reversible proton reduction by the [NiFe]-hydrogenases make them a model bioinorganic system. A highly conserved arginine residue (R355) directly above the exogenous ligand binding position of the [NiFe]-catalytic core is known to be essential for optimal function because mutation to a lysine results in lower catalytic rates. To expand on our studies of soluble hydrogenase-1 from Pyrococcus furiosus (Pf SH1), we investigated the role of R355 by site-directed-mutagenesis to a lysine (R355K) using infrared and electron paramagnetic resonance spectroscopic probes sensitive to active site redox and protonation events. It was found the mutation resulted in an altered ligand binding environment at the [NiFe] centre. A key observation was destabilization of the Nia3+–C state, which contains a bridging hydride. Instead, the tautomeric Nia+–L states were observed. Overall, the results provided insight into complex metal–ligand cooperativity between the active site and protein scaffold that modulates the bridging hydride stability and the proton inventory, which should prove valuable to design principles for efficient bioinspired catalysts. Metal–ligand cooperativity is an essential feature of bioinorganic catalysis.![]()
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Affiliation(s)
| | - Chang-Hao Wu
- Department of Biochemistry & Molecular Biology, University of Georgia Athens Georgia 30602 USA.,AskGene Pharma Inc. Camarillo CA 93012 USA
| | - Dominik K Haja
- Department of Biochemistry & Molecular Biology, University of Georgia Athens Georgia 30602 USA
| | - Soshawn A Blair
- Department of Chemistry, University of Georgia Athens Georgia 30602 USA
| | - Bryant Chica
- Department of Chemistry, Emory University Atlanta Georgia 30222 USA .,Biosciences Center, National Renewable Energy Laboratory Golden Colorado 80401 USA
| | - Michael K Johnson
- Department of Chemistry, University of Georgia Athens Georgia 30602 USA
| | - Michael W W Adams
- Department of Biochemistry & Molecular Biology, University of Georgia Athens Georgia 30602 USA.,Department of Chemistry, University of Georgia Athens Georgia 30602 USA
| | - R Brian Dyer
- Department of Chemistry, Emory University Atlanta Georgia 30222 USA
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7
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Triphos nickel(II) halide pincer complexes as robust proton reduction electrocatalysts. MOLECULAR CATALYSIS 2020. [DOI: 10.1016/j.mcat.2020.110950] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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8
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Keegan BC, Ocampo D, Shearer J. pH Dependent Reversible Formation of a Binuclear Ni 2 Metal-Center Within a Peptide Scaffold. INORGANICS 2019; 7:90. [PMID: 38046130 PMCID: PMC10691859 DOI: 10.3390/inorganics7070090] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2023] Open
Abstract
A disulfide-bridged peptide containing two Ni2+ binding sites based on the nickel superoxide dismutase protein, {Ni2(SODmds)}, has been prepared. At physiological pH (7.4) it was found that the metal sites are mononuclear with a square planar NOS2 coordination environment with the two sulfur-based ligands derived from cysteinate residues, the nitrogen ligand derived from the amide backbone and a water ligand. Furthermore, S K-edge X-ray absorption spectroscopy indicated that the two cysteinate sulfur atoms ligated to nickel are each protonated. Elevation of the pH to 9.6 results in the deprotonation of the cysteinate sulfur atoms, and yields a binuclear, cysteinate bridged Ni22+ center with each nickel contained in a distorted square planar geometry. At both pH = 7.4 and 9.6 the nickel sites are moderately air sensitive, yielding intractable oxidation products. However, at pH = 9.6 {Ni2(SODmds)} reacts with O2 at an ~3.5-fold faster rate than at pH = 7.4. Electronic structure calculations indicate the reduced reactivity at pH = 7.4 is a result of a reduction in S(3p) character and deactivation of the nucleophilic frontier molecular orbitals upon cysteinate sulfur protonation.
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Affiliation(s)
- Brenna C. Keegan
- Department of Chemistry, Trinity University, 1 Trinity Place, San Antonio, TX 78212, U.S.A
| | - Daniel Ocampo
- Department of Chemistry, Trinity University, 1 Trinity Place, San Antonio, TX 78212, U.S.A
| | - Jason Shearer
- Department of Chemistry, Trinity University, 1 Trinity Place, San Antonio, TX 78212, U.S.A
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9
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Afzal M, Usman M, Al-Lohedan HA, Tabassum S. Synthesis and characterization of heterobimetallic Sn IV-Cu II/Zn II complexes: DFT studies, cleavage potential and cytotoxic activity. J Biomol Struct Dyn 2019; 38:1130-1142. [PMID: 30885099 DOI: 10.1080/07391102.2019.1596837] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Heterobimetallic complexes [Cu(L)Sn(CH3)2(H2O)(Cl)] (3) and [Zn(L)Sn(CH3)2(H2O)(Cl)] (4) have been synthesized from their monometallic analogs [Cu(L)(H2O)(Cl)] (1) and [Zn(L)(H2O)(Cl)] (2) of Schiff base ligand (L) which were characterized by various spectroscopic and analytical methods. DFT calculations were carried out to simulate the vibrational spectra to support the anticipated structures. The interaction studies of ligand (L) and complexes (1-4) with CT-DNA were performed by employing UV-vis, and fluorescence spectroscopic techniques which revealed that heterobimetallic complexes 3 and 4 showed higher affinity with DNA due to dual mode of action as compared to monometallic complexes 1 and 2. Further, validation of the interaction studies was accomplished by carrying out molecular docking studies with DNA. Gel assay displayed that both the complexes have ability to cleave DNA efficiently and are specific minor groove binders. CuII-SnIV complex 3 cleaved pBR322 DNA via oxidative mechanism, while ZnII-SnIV complex 4 followed hydrolytic cleavage pathway. In vitro cytotoxicity evaluation of complex 3 was tested on a different cancer cell lines showing promising antitumor activity.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Mohd Afzal
- Department of Chemistry, Aligarh Muslim University, Aligarh, India
| | - Mohammad Usman
- Department of Chemistry, Aligarh Muslim University, Aligarh, India
| | - Hamad A Al-Lohedan
- Surfactant Research Chair, Department of Chemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Sartaj Tabassum
- Surfactant Research Chair, Department of Chemistry, College of Science, King Saud University, Riyadh, Saudi Arabia
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10
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Henderson RA. Protonation mechanisms of Nickel Complexes Relevant to Industrial and Biological Catalysis. JOURNAL OF CHEMICAL RESEARCH 2019. [DOI: 10.3184/030823402103172554] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The sites of protonation and the subsequent rearrangement reactions of simple nickel complexes containing hydride, thiolate and alkyl ligands are reviewed, and the relevance of these reactions to the action of certain nickelbased catalysts are discussed. Summary Protonation at the metal and ligand is central to the understanding of how both enzymes and industrial catalysts operate at the molecular level. The recurring theme in studies on the protonation of all metal complexes is that the ultimate residence of the proton is not necessarily the initial binding site, and the movement of proton between sites can occur by a variety of mechanisms. These features are also evident in the reactions of simple nickel complexes and mechanistic studies are revealing the subtle interplay between ligand and metal which are the basis of the kinetic and thermodynamic control of protonation reactions at these sites.
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Affiliation(s)
- Richard A. Henderson
- Department of Chemistry, Bedson Building, University of Newcastle, Newcastle-upon-Tyne, NE1 7RU, UK
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11
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Maiti BK, Almeida RM, Moura I, Moura JJ. Rubredoxins derivatives: Simple sulphur-rich coordination metal sites and its relevance for biology and chemistry. Coord Chem Rev 2017. [DOI: 10.1016/j.ccr.2017.10.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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12
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Greene BL, Vansuch GE, Wu CH, Adams MWW, Dyer RB. Glutamate Gated Proton-Coupled Electron Transfer Activity of a [NiFe]-Hydrogenase. J Am Chem Soc 2016; 138:13013-13021. [DOI: 10.1021/jacs.6b07789] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Brandon L. Greene
- Chemistry
Department, Emory University, Atlanta, Georgia 30322, United States
| | - Gregory E. Vansuch
- Chemistry
Department, Emory University, Atlanta, Georgia 30322, United States
| | - Chang-Hao Wu
- Department
of Biochemistry, University of Georgia, Athens, Georgia 30602, United States
| | - Michael W. W. Adams
- Department
of Biochemistry, University of Georgia, Athens, Georgia 30602, United States
| | - R. Brian Dyer
- Chemistry
Department, Emory University, Atlanta, Georgia 30322, United States
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13
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Oh S, Lee Y. Reversible Intramolecular P–S Bond Formation Coupled with a Ni(0)/Ni(II) Redox Process. Organometallics 2016. [DOI: 10.1021/acs.organomet.6b00253] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Seohee Oh
- Department
of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Yunho Lee
- Department
of Chemistry, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
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14
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Abstract
Transition metal hydride complexes are usually amphoteric, not only acting as hydride donors, but also as Brønsted-Lowry acids. A simple additive ligand acidity constant equation (LAC for short) allows the estimation of the acid dissociation constant Ka(LAC) of diamagnetic transition metal hydride and dihydrogen complexes. It is remarkably successful in systematizing diverse reports of over 450 reactions of acids with metal complexes and bases with metal hydrides and dihydrogen complexes, including catalytic cycles where these reactions are proposed or observed. There are links between pKa(LAC) and pKa(THF), pKa(DCM), pKa(MeCN) for neutral and cationic acids. For the groups from chromium to nickel, tables are provided that order the acidity of metal hydride and dihydrogen complexes from most acidic (pKa(LAC) -18) to least acidic (pKa(LAC) 50). Figures are constructed showing metal acids above the solvent pKa scales and organic acids below to summarize a large amount of information. Acid-base features are analyzed for catalysts from chromium to gold for ionic hydrogenations, bifunctional catalysts for hydrogen oxidation and evolution electrocatalysis, H/D exchange, olefin hydrogenation and isomerization, hydrogenation of ketones, aldehydes, imines, and carbon dioxide, hydrogenases and their model complexes, and palladium catalysts with hydride intermediates.
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Affiliation(s)
- Robert H Morris
- Department of Chemistry, University of Toronto , 80 Saint George Street, Toronto, Ontario M5S 3H6, Canada
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15
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Alwaaly A, Henderson RA. Slow proton transfer to coordinated carboxylates: studies on [Ni(O 2CR){PhP(CH 2CH 2PPh 2) 2}] + (R = Et or Ph). J COORD CHEM 2015. [DOI: 10.1080/00958972.2015.1047773] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Ahmed Alwaaly
- School of Chemistry, Newcastle University, Newcastle upon Tyne, UK
- Department of Chemistry, College of Science, University of Basrah, Basrah, Iraq
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16
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Alwaaly A, Clegg W, Henderson RA, Probert MR, Waddell PG. Mechanisms and rates of proton transfer to coordinated carboxydithioates: studies on [Ni(S 2CR){PhP(CH 2CH 2PPh 2) 2}] + (R = Me, Et, Bu n or Ph). Dalton Trans 2015; 44:3307-17. [DOI: 10.1039/c4dt03543g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Kinetics of protonation of [Ni(S2CR)(PhP{CH2CH2PPh2}2)]+ (R = Me, Et, Bun or Ph) with HCl reveals hydrogen-bonded precursor and subsequent chelate opening.
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Affiliation(s)
- Ahmed Alwaaly
- School of Chemistry
- Newcastle University
- Newcastle upon Tyne
- UK
- Department of Chemistry
| | - William Clegg
- School of Chemistry
- Newcastle University
- Newcastle upon Tyne
- UK
| | | | | | - Paul G. Waddell
- School of Chemistry
- Newcastle University
- Newcastle upon Tyne
- UK
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17
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Alwaaly A, Clegg W, Harrington RW, Petrou AL, Henderson RA. Mechanism of proton transfer to coordinated thiolates: encapsulation of acid stabilizes precursor intermediate. Dalton Trans 2015; 44:11977-83. [DOI: 10.1039/c5dt01716e] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrogen bonded intermediate in protonation of [Ni(thiolate)(triphos)]+ by 2,6-lutidinium is stabilized by encapsulation of the acid by phenyl groups of triphos.
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Affiliation(s)
- Ahmed Alwaaly
- School of Chemistry
- Newcastle University
- Newcastle upon Tyne
- UK
- Department of Chemistry
| | - William Clegg
- School of Chemistry
- Newcastle University
- Newcastle upon Tyne
- UK
| | | | - Athinoula L. Petrou
- Department of Chemistry
- Inorganic Chemistry Laboratory
- National and Kapodistrian University of Athens
- 157 71 Athens
- Greece
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18
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Zhang J, Adhikary A, King KM, Krause JA, Guan H. Substituent effects on Ni–S bond dissociation energies and kinetic stability of nickel arylthiolate complexes supported by a bis(phosphinite)-based pincer ligand. Dalton Trans 2012; 41:7959-68. [DOI: 10.1039/c2dt30407d] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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19
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Petrou AL, Koutselos AD, Wahab HS, Clegg W, Harrington RW, Henderson RA. Kinetic and Theoretical Studies on the Protonation of [Ni(2-SC6H4N){PhP(CH2CH2PPh2)2}]+: Nitrogen versus Sulfur as the Protonation Site. Inorg Chem 2011; 50:847-57. [DOI: 10.1021/ic101444d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | | | | | - William Clegg
- School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, U.K
| | - Ross W. Harrington
- School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, U.K
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20
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Zhang J, Medley CM, Krause JA, Guan H. Mechanistic Insights into C−S Cross-Coupling Reactions Catalyzed by Nickel Bis(phosphinite) Pincer Complexes. Organometallics 2010. [DOI: 10.1021/om100816d] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jie Zhang
- Department of Chemistry, University of Cincinnati, P.O. Box 21072, Cincinnati, Ohio 45221-0172, United States
| | - Christopher M. Medley
- Department of Chemistry, University of Cincinnati, P.O. Box 21072, Cincinnati, Ohio 45221-0172, United States
| | - Jeanette A. Krause
- Department of Chemistry, University of Cincinnati, P.O. Box 21072, Cincinnati, Ohio 45221-0172, United States
| | - Hairong Guan
- Department of Chemistry, University of Cincinnati, P.O. Box 21072, Cincinnati, Ohio 45221-0172, United States
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21
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Boudreau J, Grenier-Desbiens J, Fontaine FG. MS-TOF Study of the Formation of Thiolato-Bridged Rhodium Oligomers. Eur J Inorg Chem 2010. [DOI: 10.1002/ejic.200901201] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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22
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Canaguier S, Vaccaro L, Artero V, Ostermann R, Pécaut J, Field MJ, Fontecave M. Cyclopentadienyl ruthenium-nickel catalysts for biomimetic hydrogen evolution: electrocatalytic properties and mechanistic DFT studies. Chemistry 2010; 15:9350-64. [PMID: 19670195 DOI: 10.1002/chem.200900854] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The new dinuclear nickel-ruthenium complexes [Ni(xbsms)RuCp(L)][PF(6)] (H(2)xbsms = 1,2-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)benzene; Cp(-) = cyclopentadienyl; L = DMSO, CO, PPh(3), and PCy(3)) are reported and are bioinspired mimics of NiFe hydrogenases. These compounds were characterized by X-ray diffraction techniques and display novel structural motifs. Interestingly, [Ni(xbsms)RuCpCO][PF(6)] is stereochemically nonrigid in solution and an isomerization mechanism was derived with the help of density functional theory (DFT) calculations. Because of an increased electron density on the metal centers [Eur. J. Inorg. Chem. 2007, 18, 2613-2626] with respect to the previously described [Ni(xbsms)Ru(CO)(2)Cl(2)] and [Ni(xbsms)Ru(p-cymene)Cl](+) complexes, [Ni(xbsms)RuCp(dmso)][PF(6)] catalyzes hydrogen evolution from Et(3)NH(+) in DMF with an overpotential reduced by 180 mV and thus represents the most efficient NiFe hydrogenase functional mimic. DFT calculations were carried out with several methods to investigate the catalytic cycle and, coupled with electrochemical measurements, allowed a mechanism to be proposed. A terminal or bridging hydride derivative was identified as the active intermediate, with the structure of the bridging form similar to that of the Ni-C active state of NiFe hydrogenases.
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Affiliation(s)
- Sigolène Canaguier
- Laboratoire de Chimie et Biologie des Métaux, Université Joseph Fourier, Grenoble, France
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van der Vlugt J, Reek J. Neutral Tridentate PNP Ligands and Their Hybrid Analogues: Versatile Non-Innocent Scaffolds for Homogeneous Catalysis. Angew Chem Int Ed Engl 2009; 48:8832-46. [DOI: 10.1002/anie.200903193] [Citation(s) in RCA: 380] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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van der Vlugt J, Reek J. Neutrale dreizähnige PNP-Liganden und deren Hybrid-Analoga: vielseitige Liganden für die kooperative homogene Katalyse. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200903193] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Fontecilla-Camps JC. Structure and Function of [NiFe]-Hydrogenases. METAL-CARBON BONDS IN ENZYMES AND COFACTORS 2009. [DOI: 10.1039/9781847559333-00151] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
[NiFe(Se)]-hydrogenases are hetero-dimeric enzymes present in many microorganisms where they catalyze the oxidation of molecular hydrogen or the reduction of protons. Like the other two types of hydrogen-metabolizing enzymes, the [FeFe]- and [Fe]-hydrogenases, [NiFe]-hydrogenases have a Fe(CO)x unit in their active sites that is most likely involved in hydride binding. Because of their complexity, hydrogenases require a maturation machinery that involves several gene products. They include nickel and iron transport, synthesis of CN− (and maybe CO), formation and insertion of a FeCO(CN−)2 unit in the apo form, insertion of nickel and proteolytic cleavage of a C-terminal stretch, a step that ends the maturation process. Because the active site is buried in the structure, electron and proton transfer are required between this site and the molecular surface. The former is mediated by either three or one Fe/S cluster(s) depending on the enzyme. When exposed to oxidizing conditions, such as the presence of O2, [NiFe]-hydrogenases are inactivated. Depending on the redox state of the enzyme, exposure to oxygen results in either a partially reduced oxo species probably a (hydro)peroxo ligand between nickel and iron or a more reduced OH– ligand instead. Under some conditions the thiolates that coordinate the NiFe center can be modified to sulfenates. Understanding this process is of biotechnological interest for H2 production by photosynthetic organisms.
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Affiliation(s)
- Juan C. Fontecilla-Camps
- Laboratoire de Cristallographie et de Cristallogenèse des Proteines, Institut de Biologie Structurale J. P. Ebel (CEA-CNRS-UJF) 41 rue Jules Horowitz F-38027 Grenoble Cédex 1 France
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van der Vlugt JI, Lutz M, Pidko EA, Vogt D, Spek AL. Cationic and neutral Ni(II) complexes containing a non-innocent PNP ligand: formation of alkyl and thiolate species. Dalton Trans 2008:1016-23. [PMID: 19173084 DOI: 10.1039/b814806f] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The synthesis and characterization of a series of cationic and neutral Ni-complexes with the non-innocent PNP(tBu) pincer ligand is discussed. Starting with the dicationic complex , [Ni(PNP(tBu))(NCMe)](BF(4))(2), a small series of dicationic and monocationic Ni(II) complexes has been prepared. Substitution with tert-butyl isocyanide and azide occurs readily in MeCN solution. IR spectroscopy provided a practical handle to access the formal valence state of the ligand. For the mono- and dicationic tert-butyl isocyanide species and the main vibrational bands in the IR spectra were reproduced quantitatively by DFT theoretical calculations, showing good agreement with the experimentally observed Deltanu upon dearomatization of the PNP(tBu) backbone. Using a selective dearomatization-reprotonation methodology the mononuclear Ni-thiolate species and are cleanly generated and their structures have been determined by X-ray crystal structure determination. Alternatively, starting from the monocationic species [Ni(PNP(tBu))Cl]BF(4), neutral alkyl derivatives are easily available in a two-step procedure, and these species have been spectroscopically characterized.
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Affiliation(s)
- Jarl Ivar van der Vlugt
- Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, MB, Eindhoven, the Netherlands.
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Lee CM, Chiou TW, Chen HH, Chiang CY, Kuo TS, Liaw WF. Mononuclear Ni(II)-Thiolate Complexes with Pendant Thiol and Dinuclear Ni(III/II)-Thiolate Complexes with Ni···Ni Interaction Regulated by the Oxidation Levels of Nickels and the Coordinated Ligands. Inorg Chem 2007; 46:8913-23. [PMID: 17867675 DOI: 10.1021/ic700719h] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Compared to [Ni(II)(SePh)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SH))]- (1a) and [Ni(II)(Cl)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SH))]- (3a) with a combination of the intramolecular [Ni...H-S] and [Ni-S...H-S] interactions, complexes [NiII(SePh)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SH))]- (1b) and [Ni(II)(Cl)(P (o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SH))]- (3b) with intramolecular [Ni...H-S] interaction exhibit lower nu(S-H) stretching frequencies (2137 and 2235 cm(-1) for 1b and 3b vs 2250 and 2287 cm(-1) for 1a and 3a, respectively) and smaller torsion angles (27.2 degrees for 3b vs 58.9 and 59.1 degrees for 1a and 3a, respectively). The pendant thiol interaction modes of 1a, 3a, and 3b in the solid state are controlled by the solvent pairs of crystallization. Oxygen oxidation of dinuclear [Ni(II)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SH))](2) (4) yielded thermally stable dinuclear [Ni(III)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-mu-S))](2) (5). The two paramagnetic d(7) Ni(III) cores (S = 1/2) with antiferromagnetic coupling (J = -3.13 cm(-1)) rationalize the diamagnetic property of 5. The fully delocalized mixed-valence [Ni(II)-Ni(III)] complexes [Ni2(P(o-C(6)H(3)-3-SiMe(3)-2-S)(3))(2)]- (6) and [Ni(2)(P(o-C(6)H(3)-3-SiMe(3)-2-S)(3))(P(o-C(6)H(3)-3-SiMe(3)-2-S)(2)(o-C(6)H(3)-3-SiMe(3)-2-SCH(3)))] (7) were isolated upon the reduction of 5 and the methylation of 6, respectively. The electronic perturbation from the sulfur methylation of 6 triggers the stronger Ni...Ni interaction and the geometrical rearrangement from the diamond shape of the [NiS(2)Ni] core to the butterfly structure of [Ni(mu-S)(2)Ni] to yield 7 with Ni...Ni distances of 2.6088(1) A. The distinctly different Ni...Ni distances (2.6026(7) for 5 and 2.8289(15) A for 6) and the coordination number of the nickels indicate a balance of geometrical requirements for different oxidation levels of [PS(3)Ni-NiPS(3)] cores of 5 and 6.
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Affiliation(s)
- Chien-Ming Lee
- Department of Chemistry, National Tsing Hua University, Hsinchu 30043, Taiwan
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Desrochers PJ, Duong DS, Marshall AS, Lelievre SA, Hong B, Brown JR, Tarkka RM, Manion JM, Holman G, Merkert JW, Vicic DA. Nickel−Cysteine Binding Supported by Phosphine Chelates. Inorg Chem 2007; 46:9221-33. [PMID: 17854178 DOI: 10.1021/ic701150q] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The effect of chelating phosphines was tested on the structure and pH-dependent stability of nickel-cysteine binding. (1,2-Bis(diphenylphosphino)ethane (dppe) and 1,1,1-tris[(diphenylphosphino)methyl]ethane (triphos) were used with three different cysteine derivatives (L-cysteine, Cys; L-cysteine ethyl ester, CysEt; cystamine, CysAm) to prepare complexes of the form (dppe)NiCysR(n+) and (triphos)NiCysR(n+) (n = 0 for Cys; n = 1 for CysEt and CysAm). Similar 31P {1H} NMR spectra for all (dppe)NiCysRn+ confirmed their square-planar P2NiSN coordination spheres. The structure of [(dppe)NiCysAm]PF6 was also confirmed by single-crystal X-ray diffraction methods. The (triphos)NiCysAm+ and (triphos)NiCysEt+ complexes were fluxional at room temperature by 31P NMR. Upon cooling to -80 degrees C, all gave spectra consistent with a P2NiSN coordination sphere with the third phosphorus uncoordinated. Temperature-dependent 31P NMR spectra showed that a trans P-Ni-S pi interaction controlled the scrambling of the coordinated triphos. In aqueous media, (dppe)NiCys was protonated at pH approximately 4-5, leading to possible formation of a nickel-cysteinethiol and eventual cysteine loss at pH < 3. The importance of N-terminus cysteine in such complexes was demonstrated by preparing (dppe)NiCys-bead and trigonal-bipyramidal Tp*NiCys-bead complexes, where Cys-bead represents cysteine anchored to polystyrene synthesis beads and Tp*- = hydrotris(3,5-dimethylpyrazolyl)borate. Importantly, results with these heterogeneous systems demonstrated the selectivity of these nickel centers for cysteine over methionine and serine and most specifically for N-terminus cysteine. The role of Ni-S pi bonding in nickel-cysteine geometries will be discussed, including how these results suggest a mechanism for the movement of electron density from nickel onto the backbone of coordinated cysteine.
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Fontecilla-Camps JC, Volbeda A, Cavazza C, Nicolet Y. Structure/function relationships of [NiFe]- and [FeFe]-hydrogenases. Chem Rev 2007; 107:4273-303. [PMID: 17850165 DOI: 10.1021/cr050195z] [Citation(s) in RCA: 1004] [Impact Index Per Article: 59.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Juan C Fontecilla-Camps
- Laboratoire de Cristallographie et Cristallogenèse des Proteines, Institut de Biologie Structurale J. P. Ebel, CEA, CNRS, Universitè Joseph Fourier, 41 rue J. Horowitz, 38027 Grenoble Cedex 1, France.
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Chen CH, Lee GH, Liaw WF. Mononuclear [NiII(L)(P-(o-C6H4S)2(o-C6H4SH))]0/1- (L = Thiolate, Selenolate, PPh3, and Cl) Complexes with Intramolecular [Ni···S···H···S]/[Ni···H···S] Interactions Modulated by the Coordinated Ligand L: Relevance to the [NiFe] Hydrogenases. Inorg Chem 2006; 45:2307-16. [PMID: 16499397 DOI: 10.1021/ic051924w] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The shift of the IR nu(S)(-)(H) frequency to lower wavenumbers for the series of complexes [Ni(II)(L)(P-(o-C6H4S)2(o-C6H4SH))]0/1- (L = PPh3 (1), Cl (6), Se-p-C6H4-Cl (5), S-C4H3S (7), SePh (4)) indicates that a trend of increasing electronic donation of the L ligands coordinated to the Ni(II) center promotes intramolecular [Ni-S...H-S] interactions. Compared to the Ni...S(H) distance, in the range of 3.609-3.802 A in complexes 1 and 4-7, the Ni...S(CH3) distances of 2.540 and 2.914 A observed in the [Ni(II)(PPh3)(P(o-C6H4S)2(o-C6H4-SCH3))] complexes (8a and 8b, two conformational isomers with the chemical shift of the thioether methyl group at delta 1.820 (-60 degrees C) and 2.109 ppm (60 degrees C) (C4D8O)) and the Ni...S(CH3) distances of 3.258 and 3.229 A found in the [Ni(II)(L)(P(o-C6H4S)2(o-C6H4-SCH3))]1- complexes (L = SPh (9), SePh (10)) also support the idea that the pendant thiol protons of the Ni(II)-thiol complexes 1/4-7 were attracted by both the sulfur of thiolate and the nickel. The increased basicity (electronic density) of the nickel center regulated by the monodentate ligand attracted the proton of the pendant thiol effectively and caused the weaker S...H bond. In addition, the pendant thiol interaction modes in the solid state (complexes 1a and 1b, Scheme 1) may be controlled by the solvent of crystallization. Compared to complex 1a, the stronger intramolecular [Ni-S...H-S] interaction (or a combination of [Ni-S...H-S]/[Ni...H-S] interactions) found in complexes 4-7 led to the weaker S-H bond strength and accelerated the oxidation (by O2) of complexes 4-7 to produce the [Ni(Y)(L)(P(o-C6H4S)3)]1- (L = Se-p-C6H4-Cl (11), SePh (12), S-C4H3S (13)) complexes.
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Affiliation(s)
- Chien-Hong Chen
- Department of Chemistry, National Tsing Hua University, Hsinchu 30043, Taiwan
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Arjmand F, Mohani B, Ahmad S. Synthesis, antibacterial, antifungal activity and interaction of CT-DNA with a new benzimidazole derived Cu(II) complex. Eur J Med Chem 2005; 40:1103-10. [PMID: 16006016 DOI: 10.1016/j.ejmech.2005.05.005] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2004] [Revised: 05/13/2005] [Accepted: 05/18/2005] [Indexed: 11/25/2022]
Abstract
The ligand [C(16)H(10)O(2)N(4)S(2)] L has been synthesized by the condensation reaction of 2-mercaptobenzimidazole and diethyloxalate. The ligand L was allowed to react with bis(ethylenediamine)Cu(II)/Ni(II) complexes to yield [C(20)H(22)N(8)S(2)Cu]Cl(2)1 and [C(20)H(22)N(8)S(2)Ni]Cl(2)2 complexes. The Ni(II) complex was synthesized only to elucidate the structure of the complex. The complexes 1 and 2 were characterized by elemental analyses, IR, NMR, EPR, UV-vis spectroscopy and molar conductance measurements. Both the complexes are ionic in nature and possess square-planar geometry. The binding of the complex 1 to calf thymus DNA was investigated spectrophotometrically. The absorption spectra of complex 1 exhibits a slight red shift with "hyperchromic effect" in presence of CTDNA. Electrochemical analysis and viscosity measurements were also carried out to ascertain the mode of binding. The complex 1 in the absence and in presence of CT DNA in aqueous solution exhibits one quasi-reversible redox wave corresponding to Cu(II)/Cu(I) redox couple at a scan rate of 0.2 V s(-1). The shift in DeltaE(p), E(1/2) and I(pa)/I(pc) values ascertain the interaction of calf thymus DNA with copper(II) complex. There is decrease in viscosity of CTDNA which indicates that the complex 1 binds to CTDNA through a partial intercalative mode. The antibacterial and antifungal studies of the [C(7)H(6)N(2)S], [C(4)H(16)N(4)Cu]Cl(2,) [C(16)H(10)N(4)S(2)O(2)] and [C(20)H(22)N(8)S(2)Cu]Cl(2) were carried out against S. aureus, E. coli and A. niger. All the results reveal that the complex 1 is highly active against the bacterial strains and also inhibits fungal growth.
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Affiliation(s)
- Farukh Arjmand
- Department of Chemistry, Aligarh Muslim University, Aligarh, UP, India.
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Synthesis of [Ni(η2-CH2C6H4R-4){PPh(CH2CH2PPh2)2}]+ (R=H, Me or MeO) and protonation reactions with HCl. J Organomet Chem 2005. [DOI: 10.1016/j.jorganchem.2005.01.034] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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MacBeth CE, Thomas JC, Betley TA, Peters JC. The Coordination Chemistry of “[BP3]NiX” Platforms: Targeting Low-Valent Nickel Sources as Promising Candidates to L3NiE and L3Ni⋮E Linkages. Inorg Chem 2004; 43:4645-62. [PMID: 15257594 DOI: 10.1021/ic049936p] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A series of divalent, monovalent, and zerovalent nickel complexes supported by the electron-releasing, monoanionic tris(phosphino)borate ligands [PhBP3] and [PhBPiPr3] ([PhBP3] = [PhB(CH2PPh2)3]-, [PhBPiPr3] = [PhB(CH2PiPr2)3]-) have been synthesized to explore fundamental aspects of their coordination chemistry. The pseudotetrahedral, divalent halide complexes [PhBP3]NiCl (1), [PhBP3]NiI (2), and [PhBPiPr3]NiCl (3) were prepared by the metalation of [PhBP3]Tl or [PhBPiPr3]Tl with (Ph3P)2NiCl2, NiI2, and (DME)NiCl2 (DME = 1,2-dimethoxyethane), respectively. Complex 1 is a versatile precursor to a series of complexes accessible via substitution reactions including [PhBP3]Ni(N3) (4), [PhBP3]Ni(OSiPh3) (5), [PhBP3]Ni(O-p-tBu-Ph) (6), and [PhBP3]Ni(S-p-tBu-Ph) (7). Complexes 2-5 and 7 have been characterized by X-ray diffraction (XRD) and are pseudotetrahedral monomers in the solid state. Complex 1 reacts readily with oxygen to form the four-electron-oxidation product, [[PhB(CH2POPh2)2(CH2PPh2)]NiCl] (8A or 8B), which features a solid-state structure that is dependent on its method of crystallization. Chemical reduction of 1 using Na/Hg or other potential 1-electron reductants generates a product that arises from partial ligand degradation, [PhBP3]Ni(eta2-CH2PPh2) (9). The more sterically hindered chloride 3 reacts with Li(dbabh) (Hdbabh = 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene) to provide the three-coordinate complex [kappa2-PhBPiPr3]Ni(dbabh) (11), also characterized by XRD. Chemical reduction of complex 1 in the presence of L-type donors produces the tetrahedral Ni(I) complexes [PhBP3]Ni(PPh3) (12) and [PhBP3]Ni(CNtBu) (13). Reduction of 3 following the addition of PMe3 or tert-butyl isocyanide affords the Ni(I) complexes [PhBPiPr3]Ni(PMe3) (14) and [PhBPiPr3]Ni(CNtBu) (15), respectively. The reactivity of these [PhBP3]NiIL and [PhBPiPr3]NiIL complexes with respect to oxidative group transfer reactions from organic azides and diazoalkanes is discussed. The zerovalent nitrosyl complex [PhBP3]Ni(NO) (16) is prepared by the reaction of 1 with excess NO or by treating 12 with stoichiometric NO. The anionic Ni(0) complexes [[kappa2-PhBP3]Ni(CO)2][nBu4N] (17) and [[kappa2-PhBPiPr3]Ni(CO)2][ASN] (18) (ASN = 5-azoniaspiro[4.4]nonane) have been prepared by reacting [PhBP3]Tl or [PhBPiPr3]Tl with (Ph3P)2Ni(CO)2 in the presence of R4NBr. The photolysis of 17 appears to generate a new species consistent with a zerovalent monocarbonyl complex which we tentatively assign as [[PhBP3]Ni(CO)][nBu4N], although complete characterization of this complex has been difficult. Finally, theoretical DFT calculations are presented for the hypothetical low spin complexes [PhBP3]Ni(NtBu), [PhBPiPr3]Ni(NtBu), [PhBPiPr3]Ni(NMe), and [PhBPiPr3]Ni(N) to consider what role electronic structure factors might play with respect to the relative stability of these species.
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Affiliation(s)
- Cora E MacBeth
- Division of Chemistry and Chemical Engineering, Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of Technology, Pasadena, California 91125, USA
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Autissier V, Zarza PM, Petrou A, Henderson RA, Harrington RW, Clegg WC. Proton Transfer to Nickel−Thiolate Complexes. 2. Rate-Limiting Intramolecular Proton Transfer in the Reactions of [Ni(SC6H4R-4)(PhP{CH2CH2PPh2}2)]+ (R = NO2, Cl, H, Me, or MeO). Inorg Chem 2004; 43:3106-15. [PMID: 15132616 DOI: 10.1021/ic0303237] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The protonation of [Ni(SC(6)H(4)R-4)(triphos)](+) (triphos = PhP[CH(2)CH(2)PPh(2)](2); R = NO(2), Cl, H, Me, or MeO) by [lutH](+) (lut = 2,6-dimethylpyridine) to form [Ni(S(H)C(6)H(4)R-4)(triphos)](2+) is an equilibrium reaction in MeCN. Kinetic studies, using stopped-flow spectrophotometry, reveal that the reactions occur by a two-step mechanism. Initially, [lutH](+) rapidly binds to the complex (K(2)(R)) in an interaction which probably involves hydrogen-bonding of the acid to the sulfur. Subsequent intramolecular proton transfer from [lutH](+) to sulfur (k(3)(R)) is slow because of both electronic and steric factors. The X-ray crystal structures of [Ni(SC(6)H(4)R-4)(triphos)](+) (R = NO(2), H, Me, or MeO) show that all are best described as square-planar complexes, with the phenyl substituents of the triphos ligand presenting an appreciable barrier to the approach of the sterically demanding [lutH](+) to the sulfur. The kinetic characteristics of the intramolecular proton transfer from [lutH](+) to sulfur have been investigated. The rate of intramolecular proton transfer exhibits a nonlinear dependence on Hammett sigma(+), with both electron-releasing and electron-withdrawing 4-R-substituents on the coordinated thiolate facilitating the rate of proton transfer (NO(2) > Cl > H > Me < MeO). The rate constants for intramolecular proton transfer correlate well with the calculated electron density of the sulfur. The temperature dependence of the rate of the intramolecular proton transfer reactions shows that deltaH() is small but increases as the 4-R-substituent becomes more electron-withdrawing [deltaH = 4.1 (MeO), 6.9 (Me), 11.4 kcal mol(-)(1) (NO(2))], while DeltaS() becomes progressively less negative [deltaS = -50.1 (MeO), -41.2 (Me), -16.4 (NO(2)) cal K(-)(1) mol(-)(1)]. Studies with [lutD](+) show that the rate of intramolecular proton transfer varies with the 4-R-substituent [(k(3)(NO)2)(H)/(k(3)(NO)2)(D) = 0.39; (k(3)(Cl))(H)/(k(3)(Cl))(D) = 0.88; (k(3)(Me))(H)/(k(3)(Me))(D) = 1.3; (k(3)(MeO))(H)/(k(3)(MeO))(D) = 1.2].
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Affiliation(s)
- Valerie Autissier
- Department of Chemistry, School of Natural Sciences, University of Newcastle, Newcastle upon Tyne, NE1 7RU UK
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Autissier V, Clegg W, Harrington RW, Henderson RA. Proton Transfer to Nickel−Thiolate Complexes. 1. Protonation of [Ni(SC6H4R-4)2(Ph2PCH2CH2PPh2)] (R = Me, MeO, H, Cl, or NO2). Inorg Chem 2004; 43:3098-105. [PMID: 15132615 DOI: 10.1021/ic030322e] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The kinetics of the equilibrium reaction between [Ni(SC(6)H(4)R-4)(2)(dppe)] (R= MeO, Me, H, Cl, or NO(2); dppe = Ph(2)PCH(2)CH(2)PPh(2)) and mixtures of [lutH](+) and lut (lut = 2,6-dimethylpyridine) in MeCN to form [Ni(SHC(6)H(4)R-4)(SC(6)H(4)R-4)(dppe)](+) have been studied using stopped-flow spectrophotometry. The kinetics for the reactions with R = MeO, Me, H, or Cl are consistent with a single-step equilibrium reaction. Investigation of the temperature dependence of the reactions shows that DeltaG = 13.6 +/- 0.3 kcal mol(-)(1) for all the derivatives but the values of DeltaH and DeltaS vary with R (R = MeO, DeltaH() = 8.5 kcal mol(-)(1), DeltaS = -16 cal K(-)(1) mol(-)(1); R = Me, DeltaH() = 10.8 kcal mol(-)(1), DeltaS = -9.5 cal K(-)(1) mol(-)(1); R = Cl, DeltaH = 23.7 kcal mol(-)(1), DeltaS = +33 cal K(-)(1) mol(-)(1)). With [Ni(SC(6)H(4)NO(2)-4)(2)(dppe)] a more complicated rate law is observed consistent with a mechanism in which initial hydrogen-bonding of [lutH](+) to the complex precedes intramolecular proton transfer. It seems likely that all the derivatives operate by this mechanism, but only with R = NO(2) (the most electron-withdrawing substituent) does the intramolecular proton transfer step become sufficiently slow to result in the change in kinetics. Studies with [lutD](+) show that the rates of proton transfer to [Ni(SC(6)H(4)R-4)(2)(dppe)] (R = Me or Cl) are associated with negligible kinetic isotope effect. The possible reasons for this are discussed. The rates of proton transfer to [Ni(SC(6)H(4)R-4)(2)(dppe)] vary with the 4-R-substituent, and the Hammett plot is markedly nonlinear. This unusual behavior is attributable to the electronic influence of R which affects the electron density at the sulfur.
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Affiliation(s)
- Valerie Autissier
- Chemistry, School of Natural Sciences, University of Newcastle, Newcastle upon Tyne, NE1 7RU UK
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BURGESS JOHN, HUBBARD COLIND. LIGAND SUBSTITUTION REACTIONS. ADVANCES IN INORGANIC CHEMISTRY 2003. [DOI: 10.1016/s0898-8838(03)54002-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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