Whited, Matthew T. and Zhu, Yanjun and Timpa, Samuel D. and Chen, Chun-Hsing and Foxman, Bruce M. and Ozerov, Oleg V. and Grubbs, Robert H. (2009) Probing the C-H Activation of Linear and Cyclic Ethers at (PNP)Ir. Organometallics, 28 (15). pp. 4560-4570. ISSN 0276-7333 http://resolver.caltech.edu/CaltechAUTHORS:20090817-144813874
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Interaction of the amido/bis(phosphine)-supported (PNP)Ir fragment with a series of linear and cyclic ethers is shown to afford, depending on substrate, products of α,α-dehydrogenation (carbenes), α,β-dehydrogenation (vinyl ethers), or decarbonylation. While carbenes are exclusively obtained from tert-amyl methyl ether, sec-butyl methyl ether (SBME), n-butyl methyl ether (NBME), and tetrahydrofuran (THF), vinyl ethers or their adducts are observed upon reaction with diethyl ether and 1,4-dioxane. Decarbonylation occurs upon interaction of (PNP)Ir with benzyl methyl ether, and a mechanism is proposed for this unusual transformation, which occurs via a series of C−H, C−O, and C−C bond cleavage events. The intermediates characterized for several of these reactions as well as the α,α-dehydrogenation of tert-butyl methyl ether (MTBE) are used to outline a reaction pathway for the generation of PNP-supported iridium(I) carbene complexes, and it is shown that the long-lived, observable intermediates are substrate-dependent and differ for the related cases of MTBE and THF. Taken together, these findings highlight the variety of pathways utilized by the electron-rich, unsaturated (PNP)Ir fragment to stabilize itself by transferring electron density to ethereal substrates through oxidative addition and/or the formation of π-acidic ligands.
|Additional Information:||Copyright © 2009 American Chemical Society. Received May 14, 2009. Publication Date (Web): July 10, 2009. We gratefully acknowledge BP (MC2 Program), the Moore Foundation (Fellowship to M.T.W.), the National Science Foundation (CHE-0517798 and CHE-0809522), the Alfred P. Sloan Foundation, and the Dreyfus Foundation for funding. S.D.T. is a student of Centenary College of Louisiana who contributed to this work in the summer of 2008 at Brandeis University; his support through an NSF-REU program (CHE-0552767) is acknowledged with gratitude. We also thank the National Science Foundation for the partial support of this work through grant CHE-0521047 for the purchase of a new X-ray diffractometer at Brandeis University and Larry Henling for crystallographic assistance at Caltech. Supporting Information: Crystallographic details for complexes 6, 7, and 9 are provided in CIF format. This material is available free of charge via the Internet at http://pubs.acs.org.|
|Official Citation:||Probing the C−H Activation of Linear and Cyclic Ethers at (PNP)Ir Matthew T. Whited, Yanjun Zhu, Samuel D. Timpa, Chun-Hsing Chen, Bruce M. Foxman, Oleg V. Ozerov, Robert H. Grubbs Organometallics 2009 28 (15), 4560-4570|
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|Deposited By:||George Porter|
|Deposited On:||08 Sep 2009 21:55|
|Last Modified:||26 Dec 2012 11:12|
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