Product kinetic energy release distributions as a probe of the energetics and mechanisms of organometallic reactions involving the formation of metallacyclobutanes in the gas phase

Koppen, Petra A. M. van; Jacobson, D. B.; Illies, Andreas J.; Bowers, Michael T.; Hanratty, Maureen A.; Beauchamp, J. L.

doi:10.1021/ja00188a007

Cited by 50 publications

(18 citation statements)

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“…Considering the second step of this process in more detail, metallacyclobutanes have been described as having three basic routes to rearrangement and decomposition: retrocyclization, β-elimination, and reductive elimination (Scheme ). , When the β-carbon is substituted, as in 1 , the β-elimination process is usually blocked, leaving [2 + 2] retrocyclization and reductive elimination of cyclopropanes as the dominant decompositionpathways. It was therefore surprising that the product obtained from heating 1 was the apparent product of β-elimination.…”

Section: Discussionmentioning

confidence: 99%

“…1 H NMR (400 MHz, C 6D6): δ 1. 64 (3 H, d, J ) 7.7 Hz, PMe), 1.57 (3 H, d, J ) 6.3 Hz, PMe), 1.29 (9 H, d, J ) 5.4 Hz, PMe 3), 1.26 (3 H, d, J ) 6.8 Hz, PMe), 1.08 (3 H, d, J ) 5.9 Hz, PMe), 1.06 (3 H, d, J ) 6.8 Hz, PMe), 0.92 (3 H, d, J ) 7.3 Hz, PMe), 0.34-0.5 (2 H, m, SiP 3 CH2), 0.2-0.3 (7 H, m, SiP3 CH2 + Ru-CH3), 0.24 (3 H, s, Si-CH3). 31 P{ 1 H} NMR (162 MHz, C6D6): δ 22.9 (ddd, J ) 24, 31, 40 Hz), 5.8 (ddd, J ) 25, 44, 324 Hz), -7.3 (ddd, J ) 28, 30, 32 Hz), -9.8 (ddd, J ) 23, 23, 23 Hz).…”

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confidence: 99%

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C−C and C−H Bond Activation at Ruthenium(II): The Stepwise Degradation of a Neopentyl Ligand to a Trimethylenemethane Ligand

1997

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Ruthenacyclobutane complexes (SiP3)(PMe3)Ru(CH2EMe2CH2) (SiP3 = MeSi(CH2PMe2)3; 1, E = C; 2, E = Si) were synthesized from (SiP3)(PMe3)RuCl2 (3) and 2 equiv of the Grignard reagents, Me3ECH2MgCl. Metallacycle 1 was found to reversibly interconvert with the allyl complex (SiP3)Ru(Me)(η3-CH2CMeCH2) (4) and PMe3 when heated above 75 °C. From the results of kinetic studies and thermolysis of labeled material, the interconversion is proposed to take place by reversible β-methyl elimination/insertion. Conversion of 1 to 4 is an endothermic process (ΔH° = 14.3 ± 1.1 kcal mol-1), but it is entropically favorable (ΔS° = 40.9 ± 2.8 cal K-1 mol-1) due to the loss of the PMe3 ligand. Activation parameters for the β-insertion were determined to be ΔH ⧧ = 26.0 ± 1.2 kcal mol-1 and ΔS ⧧ = −10.5 ± 0.9 cal K-1 mol-1. Allyl complex 4 has been isolated as a mixture of isomers (7:1 endo:exo). The mechanism of interconversion of 4 endo and 4 exo was determined by 1H{31P} NMR spectroscopy (EXSY) to be a process involving a stereochemically rigid, square-pyramidal η1-intermediate. Thermolysis of 4 leads to loss of CH4 and the production of the trimethylenemethane complex (SiP3)Ru(η4-C(CH2)3) (7). The solid state structures of 1 and 7 were determined by X-ray diffraction.

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Section: Discussionmentioning

confidence: 99%

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confidence: 99%

C−C and C−H Bond Activation at Ruthenium(II): The Stepwise Degradation of a Neopentyl Ligand to a Trimethylenemethane Ligand

1997

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“…After the barrier leading to (R)(RЈ)YCO is crossed, if excess energy cannot be channeled efficiently into vibrational and rotational energy as the complex dissociates to RYRЈϩCO, there will be a nonstatistical partitioning of the available energy into the products, yielding a P(E) that will peak significantly away from the zero of energy. 26 Several important factors likely contribute to inefficient energy randomization prior to CO elimination. Using RRKM theory for the YϩH 2 CO reaction, the rate constant for dissociation of ͑H͒͑H͒YCO to YH 2 and CO was Ϸ10 14 s Ϫ1 , which is greater than even the largest vibrational frequency in the complex.…”

Section: Translational Energy Distributionsmentioning

confidence: 99%

Dynamics of CO elimination from reactions of yttrium atoms with formaldehyde, acetaldehyde, and acetone

Schroden

Teo

Davis

2002

The Journal of Chemical Physics

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Reactions of neutral, ground-state yttrium atoms with formaldehyde, acetaldehyde, and acetone (YϩRRЈCO, where R,RЈϭH,CH 3) were studied in crossed molecular beams. At collision energies greater than 24 kcal/mol, four product channels were observed corresponding to elimination of CO, H 2 , H, and nonreactive scattering. For the dominant CO elimination channel, a large fraction ͑34%-41%͒ of the available energy appeared as kinetic energy of the products. RRKM modeling indicated this was a result of two factors: a large potential energy barrier for RЈ migration leading to (R)(RЈ)YCO and dissociation of this complex prior to complete energy randomization. The CM angular distributions were all forward-backward symmetric, indicating the existence of at least one long-lived reaction intermediate. The angular distributions ranged from being quite forwardbackward peaking for the YϩH 2 CO reaction to isotropic for Yϩ͑CH 3 ͒ 2 CO. A simple equation is derived based on statistical complex theory that relates the shape of the CM angular distributions to the structure of the dissociating complex.

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“…The chemical simplicity of the lowpressure gas-phase environment and the possibility of separating solvent effects from intrinsic bonding thermochemistry have been key factors in making this a rewarding new area of metal ion chemistry. Established techniques for determining ligandmetal bond strengths include ligand exchange equilibrium, 5,6 bracketing by exothermic ion-neutral reactions, 1 metastable ion dissociation, 7 collision-induced dissociation, [8][9][10][11][12] and photodissociation methods, [13][14][15][16][17] as well as Hess's law calculations from independently determined thermochemical data. 1 A recent, promising addition to this array of tools is the kinetic analysis of radiative association reactions (the RA kinetics approach).…”

Section: Introductionmentioning

confidence: 99%

Binding Energies of Ag⁺ and Cd⁺ Complexes from Analysis of Radiative Association Kinetics

Yang

Klippenstein

et al. 1997

J. Phys. Chem. A

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Association reactions of Cd+ with benzene and of Ag+ with acetone and several unsaturated hydrocarbons were observed in the Fourier-transform ion cyclotron resonance (FT-ICR) spectrometer. The reactions were presumed to occur by radiative association (RA) involving infrared photon emission, and the kinetics were analyzed to derive bond strengths for the ion−neutral complexes. To supply the structures, infrared frequencies, and infrared intensities required for this analysis, ab initio calculations at the Hartree−Fock (HF) and second-order Moeller−Plesset perturbation theory (MP2) levels were carried out for the reactants and the association complexes, and the results are reported. The RA kinetics analysis yielded values for the binding energies of 1.41 ± 0.2 eV for Cd+(benzene), 1.68 ± 0.2 eV for Ag+(benzene), 1.66 ± 0.2 eV for Ag+(acetone), 1.70 ± 0.2 eV for Ag+(isoprene), and 1.71 ± 0.2 eV for Ag+(2-pentene). The MP2-derived modeling gave higher (and more reliable) binding energies than the HF-derived modeling, but the HF-level modeling was found to provide estimates of useful precision, except for the Ag+(benzene) case. Binding energies were also estimated for the observed Ag+L2 complexes, and within experimental and modeling error the second ligand was found to bind with the same energy as the first. Clustering of six or more acetaldehydes with Ag+ was observed, but it was considered most likely that this reflected fast association with low-abundance polymeric impurities in the acetaldehyde sample.

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Product kinetic energy release distributions as a probe of the energetics and mechanisms of organometallic reactions involving the formation of metallacyclobutanes in the gas phase

Cited by 50 publications

References 2 publications

C−C and C−H Bond Activation at Ruthenium(II): The Stepwise Degradation of a Neopentyl Ligand to a Trimethylenemethane Ligand

C−C and C−H Bond Activation at Ruthenium(II): The Stepwise Degradation of a Neopentyl Ligand to a Trimethylenemethane Ligand

Dynamics of CO elimination from reactions of yttrium atoms with formaldehyde, acetaldehyde, and acetone

Binding Energies of Ag⁺ and Cd⁺ Complexes from Analysis of Radiative Association Kinetics

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Product kinetic energy release distributions as a probe of the energetics and mechanisms of organometallic reactions involving the formation of metallacyclobutanes in the gas phase

Cited by 50 publications

References 2 publications

C−C and C−H Bond Activation at Ruthenium(II): The Stepwise Degradation of a Neopentyl Ligand to a Trimethylenemethane Ligand

C−C and C−H Bond Activation at Ruthenium(II): The Stepwise Degradation of a Neopentyl Ligand to a Trimethylenemethane Ligand

Dynamics of CO elimination from reactions of yttrium atoms with formaldehyde, acetaldehyde, and acetone

Binding Energies of Ag+ and Cd+ Complexes from Analysis of Radiative Association Kinetics

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Product

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Binding Energies of Ag⁺ and Cd⁺ Complexes from Analysis of Radiative Association Kinetics