Large Kinetic Isotope Effects for the Protonolysis of Metal-Methyl Complexes Are Not Reliable Mechanistic Indicators
Earlier work on protonolyses of several palladium and platinum methyl complexes (with release of methane) had suggested the possibility that observation of an unusually large kinetic isotope effect, consistent with significant contributions from quantum mechanical tunneling, might be diagnostic of a mechanism involving direct protonation of the metal–methyl bond, as opposed to one proceeding via a metal hydride intermediate. By extension of these measurements to a wider set of complexes, we find no support for the proposed correlation.
Additional Information© 2011 American Chemical Society. Received: May 23, 2011. Publication Date (Web): July 18, 2011. This research was funded by BP through the Methane Conversion Cooperative (MC2) program. We thank M. Findlater and M. Brookhart for providing the PONOP complexes and Dr. David Vander Velde for help with NMR experiments.
Supplemental Material - om200432b_si_001.pdf