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Jay RM, Coates MR, Zhao H, Winghart MO, Han P, Wang RP, Harich J, Banerjee A, Wikmark H, Fondell M, Nibbering ETJ, Odelius M, Huse N, Wernet P. Photochemical Formation and Electronic Structure of an Alkane σ-Complex from Time-Resolved Optical and X-ray Absorption Spectroscopy. J Am Chem Soc 2024; 146:14000-14011. [PMID: 38713061 PMCID: PMC11117182 DOI: 10.1021/jacs.4c02077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 04/29/2024] [Accepted: 04/30/2024] [Indexed: 05/08/2024]
Abstract
C-H bond activation reactions with transition metals typically proceed via the formation of alkane σ-complexes, where an alkane C-H σ-bond binds to the metal. Due to the weak nature of metal-alkane bonds, σ-complexes are challenging to characterize experimentally. Here, we establish the complete pathways of photochemical formation of the model σ-complex Cr(CO)5-alkane from Cr(CO)6 in octane solution and characterize the nature of its metal-ligand bonding interactions. Using femtosecond optical absorption spectroscopy, we find photoinduced CO dissociation from Cr(CO)6 to occur within the 100 fs time resolution of the experiment. Rapid geminate recombination by a fraction of molecules is found to occur with a time constant of 150 fs. The formation of bare Cr(CO)5 in its singlet ground state is followed by complexation of an octane molecule from solution with a time constant of 8.2 ps. Picosecond X-ray absorption spectroscopy at the Cr L-edge and O K-edge provides unique information on the electronic structure of the Cr(CO)5-alkane σ-complex from both the metal and ligand perspectives. Based on clear experimental observables, we find substantial destabilization of the lowest unoccupied molecular orbital upon coordination of the C-H bond to the undercoordinated Cr center in the Cr(CO)5-alkane σ-complex, and we define this as a general, orbital-based descriptor of the metal-alkane bond. Our study demonstrates the value of combining optical and X-ray spectroscopic methods as complementary tools to study the stability and reactivity of alkane σ-complexes in their role as the decisive intermediates in C-H bond activation reactions.
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Affiliation(s)
- Raphael M. Jay
- Department
of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
| | - Michael R. Coates
- Department
of Physics, AlbaNova University Center, Stockholm University, 10691 Stockholm, Sweden
| | - Huan Zhao
- Center
for Free-Electron Laser Science, Department of Physics, University of Hamburg, 22761 Hamburg, Germany
| | - Marc-Oliver Winghart
- Max
Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, 12489 Berlin, Germany
| | - Peng Han
- Max
Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, 12489 Berlin, Germany
| | - Ru-Pan Wang
- Center
for Free-Electron Laser Science, Department of Physics, University of Hamburg, 22761 Hamburg, Germany
| | - Jessica Harich
- Center
for Free-Electron Laser Science, Department of Physics, University of Hamburg, 22761 Hamburg, Germany
| | - Ambar Banerjee
- Department
of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
| | - Hampus Wikmark
- Department
of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
| | - Mattis Fondell
- Institute
for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und
Energie GmbH, 12489 Berlin, Germany
| | - Erik T. J. Nibbering
- Max
Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, 12489 Berlin, Germany
| | - Michael Odelius
- Department
of Physics, AlbaNova University Center, Stockholm University, 10691 Stockholm, Sweden
| | - Nils Huse
- Center
for Free-Electron Laser Science, Department of Physics, University of Hamburg, 22761 Hamburg, Germany
| | - Philippe Wernet
- Department
of Physics and Astronomy, Uppsala University, 75120 Uppsala, Sweden
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Turner JJ, George MW, Poliakoff M, Perutz RN. Photochemistry of transition metal carbonyls. Chem Soc Rev 2022; 51:5300-5329. [PMID: 35708003 DOI: 10.1039/d1cs00826a] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The purpose of this Tutorial Review is to outline the fundamental photochemistry of metal carbonyls, and to show how the advances in technology have increased our understanding of the detailed mechanisms, particularly how relatively simple experiments can provide deep understanding of complex problems. We recall some important early experiments that demonstrate the key principles underlying current research, concentrating on the binary carbonyls and selected substituted metal carbonyls. At each stage, we illustrate with examples from recent applications. This review first considers the detection of photochemical intermediates in three environments: glasses and matrices; gas phase; solution. It is followed by an examination of the theory underpinning these observations. In the final two sections, we briefly address applications to the characterization and behaviour of complexes with very labile ligands such as N2, H2 and alkanes, concentrating on key mechanistic points, and also describe some principles and examples of photocatalysis.
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Affiliation(s)
- James J Turner
- School of Chemistry University of Nottingham, NG7 2RD, UK.
| | | | | | - Robin N Perutz
- Department of Chemistry, University of York, York, YO10 5DD, UK.
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3
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Bartlett SA, Besley NA, Dent AJ, Diaz-Moreno S, Evans J, Hamilton ML, Hanson-Heine MWD, Horvath R, Manici V, Sun XZ, Towrie M, Wu L, Zhang X, George MW. Monitoring the Formation and Reactivity of Organometallic Alkane and Fluoroalkane Complexes with Silanes and Xe Using Time-Resolved X-ray Absorption Fine Structure Spectroscopy. J Am Chem Soc 2019; 141:11471-11480. [DOI: 10.1021/jacs.8b13848] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Stuart A. Bartlett
- DySS, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0FA, U.K
- School of Chemistry, The University of Sydney, Eastern Avenue, Sydney, NSW 2006, Australia
- Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, U.K
| | - Nicholas A. Besley
- School of Chemistry, University of Nottingham, University Park NG7 2RD, U.K
| | - Andrew J. Dent
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, U.K
| | - Sofia Diaz-Moreno
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, U.K
| | - John Evans
- DySS, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0FA, U.K
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, U.K
- Chemistry, University of Southampton, Southampton SO17 1BJ, U.K
| | - Michelle L. Hamilton
- DySS, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0FA, U.K
- School of Chemistry, University of Nottingham, University Park NG7 2RD, U.K
| | | | - Raphael Horvath
- School of Chemistry, University of Nottingham, University Park NG7 2RD, U.K
| | - Valentina Manici
- DySS, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0FA, U.K
- School of Chemistry, University of Nottingham, University Park NG7 2RD, U.K
| | - Xue-Zhong Sun
- School of Chemistry, University of Nottingham, University Park NG7 2RD, U.K
| | - Michael Towrie
- DySS, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0FA, U.K
- Central Laser Facility, Research Complex at Harwell, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, U.K
| | - Lingjun Wu
- School of Chemistry, University of Nottingham, University Park NG7 2RD, U.K
| | - Xiaoyi Zhang
- X-ray Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Michael W. George
- DySS, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot OX11 0FA, U.K
- School of Chemistry, University of Nottingham, University Park NG7 2RD, U.K
- Department of Chemical and Environmental Engineering, University of Nottingham Ningbo China, 199 Taikang East Road, Ningbo 315100, China
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4
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Wu X, Liu Z, Murphy TS, Sun XZ, Hanson-Heine MWD, Towrie M, Harvey JN, George MW. The effect of coordination of alkanes, Xe and CO 2 (η 1-OCO) on changes in spin state and reactivity in organometallic chemistry: a combined experimental and theoretical study of the photochemistry of CpMn(CO) 3. Faraday Discuss 2019; 220:86-104. [PMID: 31608916 DOI: 10.1039/c9fd00067d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A combined experimental and theoretical study is presented of several ligand addition reactions of the triplet fragment 3CpMn(CO)2 formed upon photolysis of CpMn(CO)3. Experimental data are provided for reactions in n-heptane and perfluoromethylcyclohexane (PFMCH), as well as in PFMCH doped with C2H6, Xe and CO2. In PFMCH we find that the conversion of 3CpMn(CO)2 to 1CpMn(CO)2(PFMCH) is much slower (τ = 18 (±3) ns) than the corresponding reactions in conventional alkanes (τ = 111 (±10) ps). We measure the effect of the coordination ability by doping PFMCH with alkane, Xe and CO2; these doped ligands form the corresponding singlet adducts with significantly variable formation rates. The reactivity as measured by the addition timescale follows the order 1CpMn(CO)2(C5H10) (τ = 270 (±10) ps) > 1CpMn(CO)2Xe (τ = 3.9 (±0.4) ns) ∼ 1CpMn(CO)2(CO2) (τ = 4.7 (±0.5) ns) > 1CpMn(CO)2(C7F14) (τ = 18 (±3) ns). Electronic structure theory calculations of the singlet and triplet potential energy surfaces and of their intersections, together with non-adiabatic statistical rate theory, reproduce the observed rates semi-quantitatively. It is shown that triplet adducts of the ligand and 3CpMn(CO)2 play a role in the kinetics, and account for the variable timescales observed experimentally.
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Affiliation(s)
- Xue Wu
- School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
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Abstract
The dioxomolybdenum(vi) complex ((t)BuClipH2)MoO2 ((t)BuClipH4 = 4,4'-di-tert-butyl-N,N'-bis(3,5-di-tert-butyl-2-hydroxyphenyl)-2,2'-diaminobiphenyl) reacts with 3,5-di-tert-butylcatechol to form oxo-free ((t)BuClip)Mo(3,5-(t)Bu2Cat). The bis(amidophenoxide)-monocatecholate complex is monomeric and exhibits a cis-β geometry in the solid state. Variable-temperature NMR data are consistent with two fluxional processes, one that interconverts several geometric isomers at low temperature, and a second that interchanges the ends of the (t)BuClip ligand at ambient temperatures. The high-temperature fluxional process can be explained by a single Bailar trigonal twist coupled with atropisomerization of the chiral diaminobiaryl backbone. Addition of excess catechol to ((t)BuClipH2)MoO2 results in formation of a dimolybdenum mono-oxo complex ((t)BuClip)Mo(μ-3,5-(t)Bu2Cat)2Mo(O)(3,5-(t)Bu2Cat). This complex, which contains a seven-coordinate bis(amidophenoxide)molybdenum center and a six-coordinate oxomolybdenum center, represents a structural hybrid between dimeric oxomolybdenumbis(catecholate) and molybdenum tris(catecholate) complexes. Both mono- and dimolybdenum complexes are best formulated as containing Mo(vi), but there is structural evidence for significant π donation from the amidophenolates. ((t)BuClip)Mo(3,5-(t)Bu2Cat) binds pyridine to form a mixture of isomeric seven-coordinate adducts. The Lewis acidity of the mixed amidophenoxide-catecholate appears to be lower than its tris(catecholate) or oxobis(amidophenoxide) analogues, which manifests itself principally in relatively slow binding of pyridine to the six-coordinate complex (k = 8 × 10(4) L mol(-1) s(-1) at 0 °C) rather than in the rate of dissociation of pyridine from the seven-coordinate adduct.
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Affiliation(s)
- Sukesh Shekar
- Department of Chemistry and Biochemistry, 251 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556-5670, USA.
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Goldberg MJ, Clabes JG, Viehbeck A, Kovac CA. Chromium-Polyimide Interface Chemistry. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-108-225] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTWe have studied the reactions occurring for the deposition of chromium onto pyromellitic dianhydride -4,4′-oxydianiline (PMDA-ODA) polyimide for a wide range of metal coverages, using X-ray photoelectron spectroscopy as well as solution studies involving model compounds. A multi-step, coverage-dependent, mechanism is proposed which includes an initial electron transfer from Cr to PMDA-ODA. followed by formation of Cr-O and and Cr-N polymer-bound intermediates, At higher metal coverage, Cr-oxides and Cr-nitrides are formed which may activate the polymer for subsequent formation of Cr-carbide. No evidence was obtained in support of a model involving initial formation of a π-arene complex between chromium atoms and PMDA-ODA. In the course of this work we have shown that similarities exist between the chemistry of metal atoms in condensed phases and the reactions occurring between metal atoms and surfaces.
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Swennenhuis BH, Benjamin Cieslinski G, Brothers EN, Bengali AA. Reactivity of the M-(η2-alkyne) bond [M=Cr, W]: A kinetic and DFT study. J Organomet Chem 2010. [DOI: 10.1016/j.jorganchem.2010.01.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
Fast time-resolved infrared (TRIR) spectroscopy has been useful for studying the reactions of a wide range of organometallic alkane and noble gas complexes at ambient temperature following irradiation of metal carbonyl precursor complexes. The reactivity of organometallic alkane and xenon complexes decreases both across and down groups V, VI, and VII, and for a given metal/ligand combination the alkane and xenon complexes have similar reactivities. Systematic studies of reactivity have produced long-lived Re complexes which have allowed such complexes to be characterized using NMR spectroscopy. A new approach using liquid propane at low temperature as a solvent to monitor the interaction of such weakly coordinating ligands with transition-metal centers is outlined. TRIR studies monitoring the coordination and activation of methane and ethane in supercritical methane and liquid ethane solvents at room temperature are also reviewed.
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Dobson GR, Zhang S. Octahedral Metal Carbonyls. 68. Kinetics and Mechanism of the Displacement of Chlorobenzene by Piperidine from the Photoproduced [Chlorobenzene-Pentacarbonylchromium(0)] Solvate. J COORD CHEM 2009. [DOI: 10.1080/00958979009409184] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Gerard R. Dobson
- a Department of Chemistry and Center for Organometallic Research , University of North Texas , Demon , Texas , 76203-5068 , USA
| | - Shulin Zhang
- a Department of Chemistry and Center for Organometallic Research , University of North Texas , Demon , Texas , 76203-5068 , USA
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11
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12
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Leadbeater NE. Organometallic Photochemistry: The Study of Short-Lived Intermediates. COMMENT INORG CHEM 2006. [DOI: 10.1080/02603599808012252] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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13
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Grills DC, Huang KW, Muckerman JT, Fujita E. Kinetic studies of the photoinduced formation of transition metal–dinitrogen complexes using time-resolved infrared and UV–vis spectroscopy. Coord Chem Rev 2006. [DOI: 10.1016/j.ccr.2006.01.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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14
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Montiel-Palma V, Pattison DI, Perutz RN, Turner C. Photochemistry of Ru(etp)(CO)H2 (etp = PhP(CH2CH2PPh2)2): Fast Oxidative Addition and Coordination Following Exclusive Dihydrogen Loss. Organometallics 2004. [DOI: 10.1021/om049729x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Virginia Montiel-Palma
- Department of Chemistry, University of York, York, YO10 5DD, U.K., and Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, Col Chamilpa, Cuernavaca, Morelos, 62210 México
| | - David I. Pattison
- Department of Chemistry, University of York, York, YO10 5DD, U.K., and Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, Col Chamilpa, Cuernavaca, Morelos, 62210 México
| | - Robin N. Perutz
- Department of Chemistry, University of York, York, YO10 5DD, U.K., and Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, Col Chamilpa, Cuernavaca, Morelos, 62210 México
| | - Claire Turner
- Department of Chemistry, University of York, York, YO10 5DD, U.K., and Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Avenida Universidad 1001, Col Chamilpa, Cuernavaca, Morelos, 62210 México
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Lees AJ. Quantitative photochemistry of organometallic complexes: insight to their photophysical and photoreactivity mechanisms. Coord Chem Rev 2001. [DOI: 10.1016/s0010-8545(00)00283-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Ford PC, Bridgewater JS, Massick S, Marhenke J. Photochemical strategies for investigating organometallic intermediates relevant to catalysis mechanisms. Catal Today 1999. [DOI: 10.1016/s0920-5861(98)00456-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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20
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Breheny CJ, Kelly JM, Long C, O'Keeffe S, Pryce MT, Russell G, Walsh MM. Photochemistry of (η6-arene)Mo(CO)3and the Role of Alkane Solvents in Modifying the Reactions of Coordinatively Unsaturated Metal Carbonyl Fragments. Organometallics 1998. [DOI: 10.1021/om9801812] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Dunwoody N, Lees AJ. Quantitative Measurements of CpRh(CO)2 (Cp = η5-C5H5) Photochemistry in Various Hydrocarbon Solutions: Mechanisms for Ligand Photosubstitution and Intermolecular C−H and Si−H Bond Activation Reactions. Organometallics 1997. [DOI: 10.1021/om970855t] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nicholas Dunwoody
- Department of Chemistry, State University of New York at Binghamton, Binghamton, New York 13902-6016
| | - Alistair J. Lees
- Department of Chemistry, State University of New York at Binghamton, Binghamton, New York 13902-6016
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Affiliation(s)
- Herbert Plenio
- Institut für Anorganische und Analytische Chemie, Universität Freiburg, Albertstr. 21, 79104 Freiburg, Germany
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Lee DW, Jensen CM. Influence of arene and alkane coordination on reversible hydrogen elimination from IrXH2(H2)(PPri3)2 (X = Cl,Br,I). Inorganica Chim Acta 1997. [DOI: 10.1016/s0020-1693(97)05444-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Szymańska-Buzar T. Photochemical reactions of Group 6 metal carbonyls catalytic transformation of alkenes and alkynes. Coord Chem Rev 1997. [DOI: 10.1016/s0010-8545(96)01291-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Boese W, McFarlane K, Lee B, Rabor J, Ford PC. Photochemistry as a tool for elucidating organometallic reaction mechanisms. Coord Chem Rev 1997. [DOI: 10.1016/s0010-8545(96)01309-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Affiliation(s)
- Chris Hall
- Department of Chemistry, University of York YO1 5DD, U.K
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Purwoko AA, Tibensky SD, Lees AJ. Substrate and Solvent Influence on the Photochemical C-H Bond Activation Reactivity of (HBPz'(3))Rh(CO)(2) (Pz' = 3,5-Dimethylpyrazolyl). Inorg Chem 1996; 35:7049-7055. [PMID: 11666886 DOI: 10.1021/ic960479p] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The photochemically-induced intermolecular C-H bond activation reaction of (HBPz'(3))Rh(CO)(2) (Pz' = 3,5-dimethylpyrazolyl) has been investigated in various hydrocarbon solutions at 293 K following excitation at 366 and 458 nm. UV-visible and FTIR spectra recorded throughout photolysis illustrate that the dicarbonyl complex can be converted readily to the corresponding (HBPz'(3))Rh(CO)(R)H derivatives at each of the excitation wavelengths. The photochemistry proceeds without interference from secondary photoprocesses or thermal reactions and the reactivity has been measured quantitatively with the determination of absolute quantum efficiencies for intermolecular C-H bond activation (phi(CH)). These measurements indicate that the C-H activation reaction proceeds very efficiently (phi(CH) = 0.13-0.32) on excitation at 366 nm but is much less effective (phi(CH) = 0.0059-0.011) on photolysis at 458 nm for each of the hydrocarbon substrates. The observed dependence of phi(CH) on irradiation wavelength is consistent with different reactivities from two rapidly dissociating low-energy ligand field (LF) excited states and the generation of monocarbonyl (HBPz'(3))Rh(CO) and ligand-dechelated (eta(2)-HBPz'(3))Rh(CO)(2) intermediates upon UV and visible excitation, respectively. The former species is attributed to be responsible for the unusually efficient C-H bond activation, whereas it is suggested that the latter complex effectively lowers the quantum efficiency by undergoing a facile eta(2)-->eta(3) ligand rechelation process. Significantly, the photoefficiencies are found to be unaffected on increasing the dissolved CO concentration, illustrating that the monocarbonyl reaction intermediate is extremely short-lived and is solvated before CO is able to coordinate. Additionally, the lack of a [CO] dependence on phi(CH) indicates that this solvated intermediate is not subject to a competitive back-reaction with CO prior to the C-H activation step, illustrating that the quantum efficiencies in (HBPz'(3))Rh(CO)(2) appear to be solely determined by the branching ratio between the dissociative and nondissociative routes. At any particular excitation wavelength the photoefficiencies are observed to be similar across the series of alkanes but are significantly reduced for the aromatic solvents, even though the aryl hydrido photoproducts are found to be more thermodynamically stable. These phi(CH) differences are also rationalized in terms of photophysical effects on the upper LF level and are related to variations in the nonradiative relaxation rates for the excited (HBPz'(3))Rh(CO)(2) complex in the hydrocarbon solutions.
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Affiliation(s)
- Agus A. Purwoko
- Department of Chemistry, State University of New York at Binghamton, Binghamton, New York 13902-6016
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29
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Lee DW, Jensen CM. Substitution of η2-Dihydrogen by Toluene and Alkanes in IrXH2(H2)(PPri3)2 Complexes. J Am Chem Soc 1996. [DOI: 10.1021/ja9619014] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Do W. Lee
- Department of Chemistry, University of Hawaii Honolulu, Hawaii 96822
| | - Craig M. Jensen
- Department of Chemistry, University of Hawaii Honolulu, Hawaii 96822
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30
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Chambers RD, Sandford G, Shah A. Perfluorocarbons as Novel Reaction Media for Photooxidation Reactions. SYNTHETIC COMMUN 1996. [DOI: 10.1080/00397919608003538] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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31
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Purwoko AA, Lees AJ. Photochemical C−H Bond Activation Reactivity of (HBPz‘3)Rh(CO)2 (Pz‘ = 3,5-Dimethylpyrazolyl) in Alkane Solutions. Inorg Chem 1996. [DOI: 10.1021/ic951199x] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Agus A. Purwoko
- Department of Chemistry, Binghamton University, State University of New York, Binghamton, New York 13902-6016
| | - Alistair J. Lees
- Department of Chemistry, Binghamton University, State University of New York, Binghamton, New York 13902-6016
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32
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Matrix-isolation studies of alkyne complexes in the photochemical reactions of Mo(CO)6 with alkynes. J Organomet Chem 1995. [DOI: 10.1016/0022-328x(95)05481-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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33
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Pereira SM, Paul Savage G, Simpson GW. Perfluorohexane As a Novel Reaction Medium For Bromination Reactions. SYNTHETIC COMMUN 1995. [DOI: 10.1080/00397919508012663] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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34
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Some reactions of metal atoms with arenes illustrating the importance of half sandwich molecules, M(arene), as reaction intermediates. J Organomet Chem 1995. [DOI: 10.1016/0022-328x(94)05104-j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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