Two reversible sigma-bond metathesis pathways for B-B bond activation to give borylpalladium complexes are demonstrated in the reaction of eta(2)-(Si-H)Pd(0) complexes with B(2)pin(2). These two pathways are connected by fluxional behavior of the Si-H bond and can be efficiently controlled by the appropriate choice of phosphine ligand, enabling the selective synthesis of two types of five-coordinate borylpalladium complexes.