A single Pd(0) center carries a fixed pair of spectator ligands and repeats a three-step turnover: oxidative addition inserts the metal into an R–X bond of the aryl-halide substrate, raising its formal oxidation state from Pd(0) to Pd(II) and expanding its coordination sphere. Transmetalation exchanges the halide for an organic group delivered by a second metal reagent (an aryl-boron species, as in a Suzuki coupling), so the metal now holds both organic fragments. Reductive elimination couples those two fragments into the C–C bonded product, releases it from the metal, and drops the center back to Pd(0) — regenerating the exact catalyst that started the cycle.
- Cycle speed — scales how fast the three stages advance; the catalyst geometry and coordination sphere respond identically at every speed, only the pacing changes.
- Play / Pause — freezes the current stage in place so the coordination sphere and ligand geometry can be inspected from any angle (drag to orbit).
- Reset — clears the cycle counter and returns the catalyst to Pd(0) at the start of stage 1.
- Cycle counter — the catalyst is never consumed: it turns over the same coordination sphere once per completed cycle, which is the defining feature of catalysis versus a stoichiometric reaction.