Divergent CO2 Activation by Tuning the Lewis Acid in Iron-Based Bimetallic Systems

摘要

Bimetallic motifs mediate the selective activation and functionalization of CO2 in metalloenzymes and some recent synthetic systems. In this work, we build on the nascent concept of bimetallic frustrated Lewis pairs (FLPs) to investigate the activation and reduction of CO2. Using the Fe~0 fragment (depe)2Fe (depe = 1,2-bis(diethylphosphino)ethane) as base, we modify the nature of the partner Lewis acid to accomplish a divergent and highly chemoselective reactivity towards CO2. Au(PMe2Ar)~+ irreversibly dissociates CO2, Zn(C6F5)2 and B(C6F5)3 yield different CO2 adducts stabilized by push-pull interactions, while Al(C6F5)3 leads to a rare heterobimetallic C-O bond cleavage, and thus to contrasting reduced products after exposure to dihydrogen. Computational investigations provide a rationale for the divergent reactivity, while Energy Decomposition Analysis-Natural Orbital for Chemical Valence (EDA-NOCV) method substantiates the heterobimetallic bonding situation.