Single-site palladium on sulfur-doped carbon for olefin alkoxycarbonylation: Performance determined by coordination environments

Alkoxycarbonylation of alkenes has rarely been studied in heterogeneous catalysis with heterogeneous single-metal-site catalysts (HSMSCs). Engineering the coordination environment and identifying the nature of different active sites for HSMSCs are more challenging. Herein, we elaborately construct diverse coordination surroundings of a single Pd site on sulfur-doped carbon (Pd–Sx/S–C, where x indicates 1, 2, and 4) via changing the thermal treatment conditions, exhibiting distinct reactivity and regioselectivity in olefin alkoxycarbonylation dispensing with mineral acid promoter. Pd–S1/S–C exhibits the highest catalytic activity with the activity (TOF) of 1,471 molproduct/(molPd⋅h) and the ratio of linear to branched esters of 4.6 for 1-butene alkoxycarbonylation. The activity (TOF) could reach as high as 4,174 molproduct/(molPd⋅h) for ethene substrate. Coordination-dependent catalytic performance is rationalized by possible reaction pathways, demonstrating the evolution of the active species during the key steps of alkene activation, CO activation and insertion, as well as chlorine-assisted alcoholysis and nucleophilic attack.