(540e) Molecular Active Sites in Heterogeneous Ir-La/C Catalyzed Carbonylation of Methanol to Acetates

We report that when Ir and La halides are deposited on carbon, exposure to CO spontaneously generates a discrete molecular heterobimetallic structure, containing an Ir-La covalent bond that acts as a highly active, selective, and stable heterogeneous catalyst for the carbonylation of methanol to produce acetic acid.  This catalyst exhibits a very high productivity of ~1.5 mole acetyl/mole Ir•s with >99% selectivity to acetyl (acidic acid and methyl acetate) without detectable loss in activity or selectivity for more than one month of continuous operation.  The enhanced activity can be mechanistically rationalized by the presence of La within the ligand sphere of the discrete molecular Ir-La heterobimetallic structure which acts as a Lewis acid to accelerate the normally rate-limiting CO insertion in Ir catalyzed carbonylation.