Delineating the critical role of acid additives in Mn-catalysed C-H bond functionalisation processes

Addition of co-catalytic Cy2NH to Mn-catalysed C-H bond activation reactions suggests that the conjugate acid, Cy2NH2X, influences catalysis. Here, acids are shown to positively influence C-H bond alkenylation catalysis involving alkynes. For certain types of alkynes an acid additive is critical to catalysis. In stark contrast, acids retard catalysis involving acrylates. [Cy2NH2]X salts also play a key role in thwarting catalyst degradation to manganese clusters. Our findings enable unreactive substrates to be alkenylated.