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Electrophilic, Ambiphilic, and Nucleophilic C−H Bond Activation: Understanding the Electronic Continuum of C−H Bond Activation Through Transition-State and Reaction Pathway Interaction Energy Decompositions

Ess, Daniel H. and Goddard, William A., III and Periana, Roy A. (2010) Electrophilic, Ambiphilic, and Nucleophilic C−H Bond Activation: Understanding the Electronic Continuum of C−H Bond Activation Through Transition-State and Reaction Pathway Interaction Energy Decompositions. Organometallics, 29 (23). pp. 6459-6472. ISSN 0276-7333. http://resolver.caltech.edu/CaltechAUTHORS:20110103-134227040

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Abstract

The potential energy and interaction energy profiles for metal- and metal−ligand-mediated alkane C−H bond activation were explored using B3LYP density functional theory (DFT) and the absolutely localized molecular orbital energy decomposition analysis (ALMO-EDA). The set of complexes explored range from late transition metal group 10 (Pt and Pd) and group 11 (Au) metal centers to group 7−9 (Ir, Rh, Ru, and W) metal centers as well as a group 3 Sc complex. The coordination geometries, electron metal count (d^8, d^6, d^4, and d^0), and ligands (N-heterocycles, O-donor, phosphine, and Cp*) are also diverse. Quantitative analysis using ALMO-EDA of both directions of charge-transfer stabilization (occupied to unoccupied orbital stabilization) energies between the metal−ligand fragment and the coordinated C−H bond in the transition state for cleavage of the C−H bond allows classification of C−H activation reactions as electrophilic, ambiphilic, or nucleophilic on the basis of the net direction of charge-transfer energy stabilization. This bonding pattern transcends any specific mechanistic or bonding paradigm, such as oxidative addition, σ-bond metathesis, or substitution. Late transition metals such as Au(III), Pt(II), Pd(II), and Rh(III) metal centers with N-heterocycle, halide, or O-donor ligands show electrophilically dominated reaction profiles with forward charge-transfer from the C−H bond to the metal, leading to more stabilization than reverse charge transfer from the metal to the C−H bond. Transition states and reaction profiles for d^6 Ru(II) and Ir(III) metals with Tp and acac ligands were found to have nearly equal forward and reverse charge-transfer energy stabilization. This ambiphilic region also includes the classically labeled electrophilic cationic species Cp*(PMe_3)Ir(Me). Nucleophilic character, where the metal to C−H bond charge-transfer interaction is most stabilizing, was found in metathesis reactions with W(II) and Sc(III) metal center complexes in reactions as well as late transition metal Ir(I) and Rh(I) pincer complexes that undergo C−H bond insertion. Comparison of pincer ligands shows that the PCP ligand imparts more nucleophilic character to an Ir metal center than a deprotonated PNP ligand. The PCP and POCOP ligands do not show a substantial difference in the electronics of C−H activation. It was also found that Rh(I) is substantially more nucleophilic than Ir(I). Lastly, as a qualitative approximation, investigation of transition-state fragment orbital energies showed that relative frontier orbital energy gaps correctly reflect electrophilic, ambiphilic, or nucleophilic charge-transfer stabilization patterns.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/om100879y DOIArticle
http://pubs.acs.org/doi/full/10.1021/om100879yPublisherArticle
ORCID:
AuthorORCID
Goddard, William A., III0000-0003-0097-5716
Periana, Roy A.0000-0001-7838-257X
Additional Information:© 2010 American Chemical Society. Received September 10, 2010. Publication Date (Web): October 29, 2010. D.H.E. thanks Brigham Young University for financial (start-up) and computer support (Fulton Supercomputing Lab) as well as the Materials and Process Simulation Center at Caltech for computer support. D.H.E. thanks Dr. Rustam Khaliullin for his help in using the ALMO-EDA method in Q-Chem. R.A.P. thanks Scripps Florida and Chevron for financial support. This work was partially 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 Number DE-SC0001298.
Funders:
Funding AgencyGrant Number
Brigham Young UniversityUNSPECIFIED
Scripps FloridaUNSPECIFIED
Department of Energy (DOE)DE-SC0001298
Chevron CorporationUNSPECIFIED
Record Number:CaltechAUTHORS:20110103-134227040
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20110103-134227040
Official Citation:Electrophilic, Ambiphilic, and Nucleophilic C−H Bond Activation: Understanding the Electronic Continuum of C−H Bond Activation Through Transition-State and Reaction Pathway Interaction Energy Decompositions Daniel H. Ess, William A. Goddard III, Roy A. Periana Organometallics 2010 29 (23), 6459-6472
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21549
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:25 Jan 2011 22:48
Last Modified:27 Apr 2017 18:47

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