Tracking C-H activation with orbital resolution

• Published in: Science (American Association for the Advancement of Science) 2023-06, Vol.380 (6648), p.955-960
• Main Authors: Jay, Raphael M, Banerjee, Ambar, Leitner, Torsten, Wang, Ru-Pan, Harich, Jessica, Stefanuik, Robert, Wikmark, Hampus, Coates, Michael R, Beale, Emma V, Kabanova, Victoria, Kahraman, Abdullah, Wach, Anna, Ozerov, Dmitry, Arrell, Christopher, Johnson, Philip J M, Borca, Camelia N, Cirelli, Claudio, Bacellar, Camila, Milne, Christopher, Huse, Nils, Smolentsev, Grigory, Huthwelker, Thomas, Odelius, Michael, Wernet, Philippe
• Format: Article
• Language: English
• Subjects: Carbon monoxide; Chemical reactions; Electron states; Heavy metals; Hydrogen bonding; Hydrogen bonds; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Palladium; Rhodium; X-ray spectroscopy
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.adf8042

Transition metal reactivity toward carbon-hydrogen (C-H) bonds hinges on the interplay of electron donation and withdrawal at the metal center. Manipulating this reactivity in a controlled way is difficult because the hypothesized metal-alkane charge-transfer interactions are challenging to access experimentally. Using time-resolved x-ray spectroscopy, we track the charge-transfer interactions during C-H activation of octane by a cyclopentadienyl rhodium carbonyl complex. Changes in oxidation state as well as valence-orbital energies and character emerge in the data on a femtosecond to nanosecond timescale. The x-ray spectroscopic signatures reflect how alkane-to-metal donation determines metal-alkane complex stability and how metal-to-alkane back-donation facilitates C-H bond cleavage by oxidative addition. The ability to dissect charge-transfer interactions on an orbital level provides opportunities for manipulating C-H reactivity at transition metals.