Catalytic Decarboxylative Coupling of Allyl Acetate:Role of the Metal Centers in the Organometallic Cluster Cations [CH3Cu2]+, [CH3AgCu]+, and [CH3Ag2]+.

Metal-catalyzed decarboxylative couplingreactions offer new opportunitiesfor formation of C–C bonds. Here, multistage ion trap massspectrometry experiments together with DFT calculations are used toexamine the role of the metal centers in coinage metal cluster catalyzeddecarboxylative coupling of allyl acetate in the gas phase via a simpletwo-step catalytic cycle. In step 1, the metal acetate cluster cation[CH3CO2Cu2]+, [CH3CO2AgCu]+, or [CH3CO2Ag2]+is subjected to collision-induceddissociation to yield the organometallic cluster cation [CH3Cu2]+, [CH3AgCu]+, or[CH3Ag2]+, respectively. Step 2 involvessubjecting these organometallic cluster cations to ion–moleculereactions with allyl acetate with the aim of generating 1-butene andre-forming the metal acetate cluster cations to close the catalyticcycle. Experiment and theory reveal the role of the two metal centersin both steps of the gas-phase catalytic reaction. All three metalacetates undergo decarboxylation (step 1), although when competingreactions are taken into account, the yield of [CH3Cu2]+is highest (83.3%). Ion–molecule reactionsof the organometallic cations with allyl acetate all proceed at thecollision rate; however, the types of products formed and their yieldsvary considerably. For example, only [CH3Cu2]+and [CH3AgCu]+undergo the C–Cbond-coupling reaction (step 2) in yields of 52.7% and 1.2%, respectively.Overall the dicopper clusters are the superior decarboxylative couplingcatalysts, since they give the highest yields of the desired productsfor both steps 1 and 2. These results highlight that the reactivityof organometallic coinage metal clusters can be “tuned”by varying the composition of the metal core. [ABSTRACT FROM AUTHOR]