Single-Crystal to Single-Crystal Transformations: Stepwise CO₂ Insertions into Bridging Hydrides of [(NHC)CuH]₂...

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Catalysis

Background:

• Dimeric [(N-heterocyclic carbene)CuH]2 complexes typically require dimer dissociation to reactive monomers for substrate insertion.
• Understanding reaction mechanisms in solid-state transformations offers unique insights into reactivity.
• Carbon dioxide (CO2) activation by metal complexes is crucial for catalysis and carbon capture.

Purpose of the Study:

• To investigate the mechanism of CO2 insertion into dimeric [(NHC)CuH]2 complexes.
• To explore alternative reaction pathways beyond complete dimer dissociation.
• To characterize novel dicopper formate complexes formed via solid-state reactions.

Main Methods:

• Single-crystal to single-crystal (SC-SC) X-ray diffraction studies.
• Mechanistic investigation of CO2 insertion into [(IPr*OMe)CuH]2.
• Characterization of intermediate and final dicopper formate products.

Main Results:

• A new pathway for stepwise CO2 insertion into [(NHC)CuH]2 was discovered, occurring without complete dimer dissociation.
• The first CO2 insertion yielded a dicopper formate hydride complex.
• A second CO2 insertion produced a dicopper bis(formate) with two distinct bridging formate bonding modes.
• These dicopper formate complexes are unstable in solution, readily dissociating into monomers.

Conclusions:

• Dimeric copper hydride complexes can undergo CO2 insertion via a stepwise mechanism in the solid state, bypassing complete monomer formation.
• SC-SC transformations provide access to unique organometallic structures not achievable through solution chemistry.
• The findings challenge previous assumptions about the necessity of monomeric species for substrate insertion in these systems.