Activation of sp3 Carbon-Hydrogen Bonds Mediated by Bis(NHC) Iridium Complexes
The activation and functionalization of C-H bonds remains a significant challenge for organometallic chemistry, with wide implications for organic synthesis. Many transition-metal systems that initiate stochiometric C-H activation are known, but complexes capable of both C-H activation and subsequent transformations of the substrate are relative rare,1 especially for substrates with sp3 C-H bonds.2 Considering the high activity of iridium complexes in mediating C–H bond activation, in particular when bound to triazolylidene ligands,3 we became interested in investigating a range of iridium complexes containing bis(carbene) ligands for facilitating alkyl C-H bond activation.4
Herein, we describe the C-H bond cleavage of acetonitrile and nitromethane by iridium(III) complexes bearing bis(triazolylidene) ligands. Metal hydroxide species formed during the metalation step have been demonstrated to be responsible of the bond scission.5 Moreover, we will discuss opportunities to couple this alkyl fragment to substrates, potentially providing a new method for alkyl functionalization.
[1] Olafs Daugulis, James Roane, Ly Dieu Tran, Acc. Chem. Res. 2015, 48, 1053.
[2] Francisco Juliá-Hernández, Toni Moragas, Josep Cornella, Ruben Martin, Nature 2017, 545, 84.
[3] a) Kate F. Donnelly, Ralte Lalrempuia, Helge Müller-Bunz, Eric Clot, Martin Albrecht, Organometallics 2015, 34, 858. b) Ralte Lalrempuia, Helge Müller-Bunz, Martin Albrecht, Angew. Chem. Int. Ed. 2011, 50, 9969.
[4] Ángela Vivancos, Martin Albrecht, Organometallics 2017, 36, 1580.
[5] Byron J. Truscott, David J. Nelson, Cristina Lujan, Alexandra M. Z. Slawin, Steven P. Nolan, Chem. Eur. J. 2013, 19, 7904.