CENTC Researchers Characterize Methane-Metal Complex

CENTC researchers at the University of North Carolina and the University of Washington have described the first observation of a metal complex that binds methane in solution. The finding is reported in the October 23 issue of Science. The binding of methane to a metal complex is a key first step in the selective breaking of the C-H bond in methane. While the breaking of all four C-H bonds in methane is quite easy to do (think burning natural gas to heat your stove or house), breaking just one bond has proven to be quite difficult. A few metal catalysts are known to carry out this bond activation, but they have proved to be too slow, too inefficient or too expensive for widespread industrial use. The research reported in Science gives new insight into this bond activation process. This information should be useful in the quest to formulate other catalysts that may one day lead to the easy conversion of methane into other useful chemical feedstocks and fuels. The research is directly related to CENTC’s goal to utilize methane stranded in remote areas.

The Science report describes a σ-methane complex that is shown to be quite stable in solution. This report is the first observation and full characterization of a relatively long-lived σ-methane complex in solution. Nuclear magnetic resonance (NMR) spectra of the complex were obtained by protonation of a rhodium-methyl precursor at -110 °C. The complex is observed to rapidly tumble in the coordination sphere of rhodium, exchanging free and bound hydrogens. Density functional theory calculations indicate that the complex is best described as η²-C,H methane coordination to the metal.

Geometry optimized structure of 2-CH₄+ at the PBE0/BS2 level.

The authors of the report are Wesley Bernskoetter, who participated in this project as a post-doctoral fellow with Maurice Brookhart at the University of North Carolina (he is now an Assistant Professor at Brown University),Cynthia Schauer, an Associate Professor at UNC, Karen Goldberg, a Professor at UW and Director of CENTC, and Maurice Brookhart, a Professor at UNC and a CENTC Principal Investigator.

Bernskoetter, Wesley H.; Schauer, Cynthia K.; Goldberg, Karen I.; Brookhart, Maurice “Characterization of a Rhodium(I) σ-Methane Complex in Solution” Science, 326 (5952), 2009, 553-556
DOI: 10.1126/science.1177485

Related links:

Read the Science paper
UNC press release
UW press release
RSC: Chemistry World Article