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Published May 7, 2008 | Supplemental Material
Journal Article Open

Oxygen-Atom Transfer from Carbon Dioxide to a Fischer Carbene at (PNP)Ir


Dehydrogenation of the dihydride (PNP)IrH_2 with norbornylene in the presence of t-butyl methyl ether leads to formation of an iridium(I) Fischer carbene complex, (PNP)Ir═C(H)O^tBu, by double C−H activation and loss of H_2. The square planar pincer-type carbene effects quantitative oxygen-atom transfer from CO_2 (1 atm) at ambient temperature to generate t-butyl formate and (PNP)Ir−CO. The iridium carbene reacts similarly with carbonyl sulfide and phenyl isocyanate, causing sulfur-atom and nitrene-group transfer, respectively. In the absence of a hydrogen acceptor, thermolysis of (PNP)IrH_2 in t-butyl methyl ether under an atmosphere of CO_2 also results in the formation of (PNP)Ir−CO and oxidation of t-butyl methyl ether to t-butyl formate via an iridium carbene. Preliminary mechanistic studies indicate that these reactions proceed through an intermediate four-membered metallalactone.

Additional Information

© 2008 American Chemical Society. Received 12 March 2008. Published online 15 April 2008. Published in print 1 May 2008. Dr. Patricio Romero is acknowledged for helpful discussions and insight. Lawrence Henling provided crystallographic assistance, and Chris Daeffler aided with low temperature NMR studies. The authors thank the Moore Foundation (fellowship to M.T.W.) and BP (MC2 program) for generous financial support of this research.

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Supplemental Material - ja801865c-file003.cif


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