Single‐Crystal to Single‐Crystal Transformations: Stepwise CO<sub>2</sub> Insertions into Bridging Hydrides of [(NHC)CuH]<sub>2</sub> Complexes
Evan A. Patrick, Mark Bowden, Jeremy D. Erickson, R. Morris Bullock, Ba L. Tran
Abstract
Abstract Mechanistic studies of substrate insertion into dimeric [(NHC)CuH] 2 (NHC=N‐heterocyclic carbene) complexes with two bridging hydrides have been shown to require dimer dissociation to generate transient, highly reactive (NHC)Cu−H monomers in solution. Using single‐crystal to single‐crystal (SC‐SC) transformations, we discovered a new pathway of stepwise insertion of CO 2 into [(NHC)CuH] 2 without complete dissociation of the dimer. The first CO 2 insertion into dimeric [(IPr*OMe)CuH] 2 (IPr*OMe=N,N′‐bis(2,6‐bis(diphenylmethyl)‐4‐methoxy‐phenyl)imidazole‐2‐ylidene) produced a dicopper formate hydride [(IPr*OMe)Cu] 2 (μ‐1,3‐O 2 CH)(μ‐H). A second CO 2 insertion produced a dicopper bis(formate), [(IPr*OMe)Cu] 2 (μ‐1,3‐O 2 CH)(μ‐1,1‐O 2 CH), containing two different bonding modes of the bridging formate. These dicopper formate complexes are inaccessible from solution reactions since the dicopper core cleanly ruptures to monomeric complexes when dissolved in a solvent.