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Atomic Carbon as a Terminal Ligand: Studies of a Carbidomolybdenum Anion Featuring Solid-State ^(13)C NMR Data and Proton-Transfer Self-Exchange Kinetics

Greco, Jane B. and Peters, Jonas C. and Baker, Thomas A. and Davis, William M. and Cummins, Christopher C. (2001) Atomic Carbon as a Terminal Ligand: Studies of a Carbidomolybdenum Anion Featuring Solid-State ^(13)C NMR Data and Proton-Transfer Self-Exchange Kinetics. Journal of the American Chemical Society, 123 (21). pp. 5003-5013. ISSN 0002-7863. https://resolver.caltech.edu/CaltechAUTHORS:20141210-093751439

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Abstract

Anion [CMo(N[R]Ar)_3]- (R = C(CD3)_2CH_3 or tBu, Ar = 3,5-C_6H_3Me_2) containing one-coordinate carbon as a terminal substituent and related molecules have been studied by single-crystal X-ray crystallography, solution and solid-state ^(13)C NMR spectroscopy, and density functional theory (DFT) calculations. Chemical reactivity patterns for [CMo(N[R]Ar)_3]- have been investigated, including the kinetics of proton-transfer self-exchange involving HCMo(N[R]Ar)_3, the carbidomolybdenum anion's conjugate acid. While the Mo⋮C bond lengths in [K(benzo-15-crown-5)_2][CMo(N[R]Ar)_3] and the parent methylidyne, HCMo(N[R]Ar)_3, are statistically identical, the carbide chemical shift of δ 501 ppm is much larger than the δ 282 ppm shift for the methylidyne. Solid-state ^(13)C NMR studies show the carbide to have a much larger chemical shift anisotropy (CSA, 806 ppm) and smaller 95Mo−13C coupling constant (60 Hz) than the methylidyne (CSA = 447 ppm, 1J_MoC = 130 Hz). DFT calculations on model compounds indicate also that there is an increasing MoC overlap population on going from the methylidyne to the terminal carbide. The pKa of methylidyne HCMo(N[R]Ar)_3 is approximately 30 in THF solution. Methylidyne HCMo(N[R]Ar)3 and carbide [CMo(N[R]Ar)3]- undergo extremely rapid proton-transfer self-exchange reactions in THF, with k = 7 × 10^6 M^(-1) s^(-1). Besides being a strong reducing agent, carbide [CMo(N[R]Ar)_3]- reacts as a nucleophile with elemental chalcogens to form carbon−chalcogen bonds and likewise reacts with PCl_3 to furnish a carbon−phosphorus bond.


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http://dx.doi.org/10.1021/ja003548eDOIArticle
http://pubs.acs.org/doi/abs/10.1021/ja003548ePublisherArticle
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ORCID:
AuthorORCID
Peters, Jonas C.0000-0002-6610-4414
Alternate Title:Atomic Carbon as a Terminal Ligand: Studies of a Carbidomolybdenum Anion Featuring Solid-State 13C NMR Data and Proton-Transfer Self-Exchange Kinetics
Additional Information:© 2001 American Chemical Society. Received September 29, 2000. The authors are grateful for support from the National Science Foundation (CHE-9988806) and for fellowships to C.C.C. from the Alfred P. Sloan and the David and Lucile Packard Foundations. C.C.C. also wishes to thank the National Science Board for awarding him the 1998 Alan T. Waterman Award. J.B.G. is grateful for a predoctoral fellowship from the National Science Foundation, J.C.P. appreciated greatly a predoctoral fellowship from the Department of Defense, and T.A.B. benefited from the support of the MIT UROP office. Also deserving of thanks are Dr. Daniel Mindiola for help with X-ray crystallography, Dr. Jeff Simpson for helpful discussions regarding solution NMR spectroscopy, and Professor Klaus Theopold for suggesting the possibility that proton transfer was occurring on the NMR time scale. We are grateful to Professor Joseph Templeton for providing information prior to publication. G. W. wishes to thank the Natural Sciences Engineering Research Council (NSERC) of Canada for research and equipment grants. We also are grateful to Professor Almeria Natansohn (Queen’s University) for providing access to the ASX200 spectrometer.
Funders:
Funding AgencyGrant Number
NSFCHE-9988806
Alfred P. Sloan FoundationUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
National Science BoardUNSPECIFIED
NSF Predoctoral Fellowship UNSPECIFIED
National Defense Science and Engineering Graduate (NDSEG) FellowshipUNSPECIFIED
MIT Undergraduate Research Opportunity Program (UROP)UNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Issue or Number:21
Record Number:CaltechAUTHORS:20141210-093751439
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20141210-093751439
Official Citation:Atomic Carbon as a Terminal Ligand:  Studies of a Carbidomolybdenum Anion Featuring Solid-State 13C NMR Data and Proton-Transfer Self-Exchange Kinetics Jane B. Greco, Jonas C. Peters, Thomas A. Baker, William M. Davis, Christopher C. Cummins, and Gang Wu Journal of the American Chemical Society 2001 123 (21), 5003-5013
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:52534
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:11 Dec 2014 17:08
Last Modified:26 Nov 2019 11:15

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