The methodology of this study relies on the screening of three sets of CO pressure (5, 15 and 50 bar) and ten common organic solvents: toluene, anisole, acetonitrile (MeCN), dimethyl carbonate (DMC), 1,4-dioxane, dimethoxyethane (DME), ethyl acetate (EtOAc), acetone, tetrahydrofurane (THF), and N,N-dimethylformamide (DMF). There is an interplay between CO pressure and the nature of the solvent for the generation of a potential active species (Scheme 3). While this step depends of course on the coordination properties of the LB, balance should also be found in terms of CO pressure: CO may be released during the disproportionation, which is then favoured at lower pressure, but concurrently CO pressure is required for the carbonylation itself.