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Title: Transition State Characterization for the Reversible Binding of Dihydrogen to Bis(2,2'-bipyridine)rhodium(l) from Temperature- and Pressure-Dependent Experimental and Theoretical Studies

Abstract

Thermodynamic and kinetic parameters for the oxidative addition of H2 to [Rh{sup II}(bpy){sub 2}]{sup +} (bpy = 2,2'-bipyridine) to form [Rh{sup III}(H){sub 2}(bpy){sub 2}]{sup +}were determined from either the UV-vis spectrum of equilibrium mixtures of [Rh{sup II}(bpy){sub 2}]{sup +} and [Rh{sup III}(H){sub 2}(bpy){sub 2}]{sup +} or from the observed rates of dihydride formation following visible-light irradiation of solutions containing [Rh{sup III}(H){sub 2}(bpy){sub 2}]{sup +} as a function of H{sub 2} concentration, temperature, and pressure in acetone and methanol. The activation enthalpy and entropy in methanol are 10.0 kcal mol{sup -1} and -18 cal mol{sup -1} K{sup -1}, respectively. The reaction enthalpy and entropy are -10.3 kcal mol{sup -1} and -19 cal mol{sup -1} K{sup -1}, respectively. Similar values were obtained in acetone. Surprisingly, the volumes of activation for dihydride formation (-15 and -16 cm{sup 3} mol{sup -1} in methanol and acetone, respectively) are very close to the overall reaction volumes (-15 cm3 mol-1 in both solvents). Thus, the volumes of activation for the reverse reaction, elimination of dihydrogen from the dihydrido complex, are approximately zero. B3LYP hybrid DFT calculations of the transition-state complex in methanol and similar MP2 calculations in the gas phase suggest that the dihydrogen has a shortmore » H-H bond (0.823 and 0.810 Angstroms, respectively) and forms only a weak Rh-H bond (1.866 and 1.915 Angstroms, respectively). Equal partial molar volumes of the dihydrogenrhodium(I) transition state and dihydridorhodium(III) can account for the experimental volume profile found for the overall process.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914053
Report Number(s):
BNL-78621-2007-JA
Journal ID: ISSN 0020-1669; INOCAJ; TRN: US0801504
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Inorg. Chem.; Journal Volume: 45
Country of Publication:
United States
Language:
English
Subject:
10 SYNTHETIC FUELS; 43 PARTICLE ACCELERATORS; ACETONE; ENTHALPY; ENTROPY; IRRADIATION; KINETICS; METHANOL; MIXTURES; SOLVENTS; THERMODYNAMICS; NSLS; national synchrotron light source

Citation Formats

Fujita,E., Brunschwig, B., Creutz, C., Muckerman, J., Sutin, N., Szaida, D., and van Eldik, R.. Transition State Characterization for the Reversible Binding of Dihydrogen to Bis(2,2'-bipyridine)rhodium(l) from Temperature- and Pressure-Dependent Experimental and Theoretical Studies. United States: N. p., 2006. Web. doi:10.1021/ic0515498.
Fujita,E., Brunschwig, B., Creutz, C., Muckerman, J., Sutin, N., Szaida, D., & van Eldik, R.. Transition State Characterization for the Reversible Binding of Dihydrogen to Bis(2,2'-bipyridine)rhodium(l) from Temperature- and Pressure-Dependent Experimental and Theoretical Studies. United States. doi:10.1021/ic0515498.
Fujita,E., Brunschwig, B., Creutz, C., Muckerman, J., Sutin, N., Szaida, D., and van Eldik, R.. Sun . "Transition State Characterization for the Reversible Binding of Dihydrogen to Bis(2,2'-bipyridine)rhodium(l) from Temperature- and Pressure-Dependent Experimental and Theoretical Studies". United States. doi:10.1021/ic0515498.
@article{osti_914053,
title = {Transition State Characterization for the Reversible Binding of Dihydrogen to Bis(2,2'-bipyridine)rhodium(l) from Temperature- and Pressure-Dependent Experimental and Theoretical Studies},
author = {Fujita,E. and Brunschwig, B. and Creutz, C. and Muckerman, J. and Sutin, N. and Szaida, D. and van Eldik, R.},
abstractNote = {Thermodynamic and kinetic parameters for the oxidative addition of H2 to [Rh{sup II}(bpy){sub 2}]{sup +} (bpy = 2,2'-bipyridine) to form [Rh{sup III}(H){sub 2}(bpy){sub 2}]{sup +}were determined from either the UV-vis spectrum of equilibrium mixtures of [Rh{sup II}(bpy){sub 2}]{sup +} and [Rh{sup III}(H){sub 2}(bpy){sub 2}]{sup +} or from the observed rates of dihydride formation following visible-light irradiation of solutions containing [Rh{sup III}(H){sub 2}(bpy){sub 2}]{sup +} as a function of H{sub 2} concentration, temperature, and pressure in acetone and methanol. The activation enthalpy and entropy in methanol are 10.0 kcal mol{sup -1} and -18 cal mol{sup -1} K{sup -1}, respectively. The reaction enthalpy and entropy are -10.3 kcal mol{sup -1} and -19 cal mol{sup -1} K{sup -1}, respectively. Similar values were obtained in acetone. Surprisingly, the volumes of activation for dihydride formation (-15 and -16 cm{sup 3} mol{sup -1} in methanol and acetone, respectively) are very close to the overall reaction volumes (-15 cm3 mol-1 in both solvents). Thus, the volumes of activation for the reverse reaction, elimination of dihydrogen from the dihydrido complex, are approximately zero. B3LYP hybrid DFT calculations of the transition-state complex in methanol and similar MP2 calculations in the gas phase suggest that the dihydrogen has a short H-H bond (0.823 and 0.810 Angstroms, respectively) and forms only a weak Rh-H bond (1.866 and 1.915 Angstroms, respectively). Equal partial molar volumes of the dihydrogenrhodium(I) transition state and dihydridorhodium(III) can account for the experimental volume profile found for the overall process.},
doi = {10.1021/ic0515498},
journal = {Inorg. Chem.},
number = ,
volume = 45,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}