CaltechAUTHORS
  A Caltech Library Service

DFT Virtual Screening Identifies Rhodium–Amidinate Complexes As Potential Homogeneous Catalysts for Methane-to-Methanol Oxidation

Fu, Ross and Nielsen, Robert J. and Goddard, William A., III and Fortman, George C. and Gunnoe, T. Brent (2014) DFT Virtual Screening Identifies Rhodium–Amidinate Complexes As Potential Homogeneous Catalysts for Methane-to-Methanol Oxidation. ACS Catalysis, 4 (12). pp. 4455-4465. ISSN 2155-5435. http://resolver.caltech.edu/CaltechAUTHORS:20141117-094150749

[img]
Preview
PDF - Supplemental Material
See Usage Policy.

1457Kb
[img]
Preview
PDF - Supplemental Material
See Usage Policy.

5Mb

Use this Persistent URL to link to this item: http://resolver.caltech.edu/CaltechAUTHORS:20141117-094150749

Abstract

In the search for new organometallic catalysts for low-temperature selective conversion of CH_4 to CH_3OH, we apply quantum mechanical virtual screening to select the optimum combination of ligand and solvent on rhodium to achieve low barriers for CH_4 activation and functionalization to recommend for experimental validation. Here, we considered Rh because its lower electronegativity compared with Pt and Pd may allow it to avoid poisoning by coordinating media. We report quantum mechanical predictions (including implicit and explicit solvation) of the mechanisms for Rh^(III)(NN) and Rh^(III)(NN^F) complexes [where (NN) = bis(N-phenyl)benzylamidinate and (NN^F) = bis(N-pentafluorophenyl)pentafluorobenzylamidinate] to catalytically activate and functionalize methane using trifluoroacetic acid (TFAH) or water as a solvent. In particular, we designed the (NN^F) ligand as a more electrophilic analogue to the (NN) ligand, and our results predict the lowest transition state barrier (ΔG‡ = 27.6 kcal/mol) for methane activation in TFAH from a pool of four different classes of ligands. To close the catalytic cycle, the functionalization of methylrhodium intermediates was also investigated, involving carbon–oxygen bond formation via S_N2 attack by solvent, or S_R2 attack by a vanadium oxo. Activation barriers for the functionalization of methylrhodium intermediates via nucleophilic attack are lower when the solvent is water, but CH_4 activation barriers are higher. In addition, we have found a correlation between CH_4 activation barriers and rhodium–methyl bond energies that allow us to predict the activation transition state energies for future ligands, as well.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/cs5005322DOIArticle
http://pubs.acs.org/doi/abs/10.1021/cs5005322PublisherArticle
http://pubs.acs.org/doi/suppl/10.1021/cs5005322PublisherSupporting Information
ORCID:
AuthorORCID
Nielsen, Robert J.0000-0002-7962-0186
Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2014 American Chemical Society. Received: April 21, 2014, Revised: August 26, 2014, Publication Date (Web): October 20, 2014. This work was supported as part of the Center for Catalytic Hydrocarbon Functionalization, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award No. DOE DE-SC0001298.
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0001298
Subject Keywords:rhodium; catalysis; quantum mechanical screening; C−H activation; methane functionalization; amidinate; fluorinated ligands
Record Number:CaltechAUTHORS:20141117-094150749
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20141117-094150749
Official Citation:DFT Virtual Screening Identifies Rhodium–Amidinate Complexes As Potential Homogeneous Catalysts for Methane-to-Methanol Oxidation Ross Fu, Robert J. Nielsen, William A. Goddard, III, George C. Fortman, and T. Brent Gunnoe ACS Catalysis 2014, 4, pp 4455–4465
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51827
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:17 Nov 2014 21:17
Last Modified:21 Sep 2017 18:05

Repository Staff Only: item control page