A catalytic probe of the surface of colloidal palladium particles using Heck coupling reactions

A series of well-defined homopolymer-stabilized Pd colloids with varying me tal particle size was used to study the Heck coupling reaction between aryl halides and olefins. Correlation of initial reaction rates and particle si zes determined by transmission electron microscopy demonstrates that the He ck reaction is a sensitive probe of metal surface structure. The presence o f the colloid-stabilizing homopolymer affords a much more stable catalyst t han that obtained using the colloid-precursor metal complexes alone. Extrem ely high total turnover numbers (TON, moles of substrate/moles of Pd; TON = 100 000) and turnover frequencies (TOF = TON/h; TOF > 80 000) are easily a ttainable with poly(vinylpyrrolidone)-stabilized colloidal palladium in the coupling of p-bromobenzaldehyde with butyl acrylate.