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Published April 19, 2010 | Supplemental Material
Journal Article Open

Thermodynamic Studies of [H_(2)Rh(diphosphine)_2]^+ and [HRh(diphosphine)_(2)(CH_(3)CN)]^(2+) Complexes in Acetonitrile


Thermodynamic studies of a series of [H_(2)Rh(PP)_2]^+ and [HRh(PP)_(2)(CH_(3)CN)]^(2+) complexes have been carried out in acetonitrile. Seven different diphosphine (PP) ligands were selected to allow variation of the electronic properties of the ligand substituents, the cone angles, and the natural bite angles (NBAs). Oxidative addition of H_2 to [Rh(PP)_2]^+ complexes is favored by diphosphine ligands with large NBAs, small cone angles, and electron donating substituents, with the NBA being the dominant factor. Large pK_a values for [HRh(PP)_(2)(CH_(3)CN)]^(2+) complexes are favored by small ligand cone angles, small NBAs, and electron donating substituents with the cone angles playing a major role. The hydride donor abilities of [H_(2)Rh(PP)_2]^+ complexes increase as the NBAs decrease, the cone angles decrease, and the electron donor abilities of the substituents increase. These results indicate that if solvent coordination is involved in hydride transfer or proton transfer reactions, the observed trends can be understood in terms of a combination of two different steric effects, NBAs and cone angles, and electron-donor effects of the ligand substituents.

Additional Information

© 2010 American Chemical Society. Published In Issue: April 19, 2010; Article ASAP: March 24, 2010 Received: January 19, 2010. This research was funded by BP through the Methane Conversion Cooperative (MC2). D. L. DuBois would like to acknowledge the support of the Chemical Sciences program of the Office of Basic Energy Sciences, Division of Chemical Sciences, Biosciences and Geosciences of the Department of Energy and by the National Science Foundation. The Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

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August 19, 2023
October 20, 2023