The synthesis of the complexes [PdR2(SPPynPh3-n)](1, n = 1, R = C6F5; 2: n = 2, R = C6F5; 3, n = 2, R = C6F3Cl2; 4, n = 3, R = C6F5; Py = 2-pyridyl) is reported, 2-4 show N,N- and N,S-bonded isomers In slow equilibrium, For the N,S-bonded isomers of 2 and 3, the intramolecular nature of the substitution process observed (pendant Py group for coordinated Fy group), together with the restricted rotation of the fluoroaryl ligands, allows the determination of the relative directions of the entering and leaving ligands with respect to the metal center and the simultaneous motion of the SPPynPh3-n ligand with respect to the fluoroaryl rings, phis information supports the occurrence of a turnstile mechanism in a square-pyramidal intermediate, rather than the common Berry pseudorotation in a trigonal-bipyramidal intermediate. This is probably induced by the disinclination of the ligands to coordinate in the latter geometry.