AbstractThe kinetics of the formation and dissociation of Ni complexes of meso‐tartrate, malate and D‐tartrate have been investigated with a pressure jump method. In solutions of Ni‐meso‐tartrate and Ni‐malate only one relaxation time is observed, the concentration dependence of which can be explained by the equilibrium Ni2++ L2‐→ NiL. The measurements indicate that only one hydroxy group and one carboxylate group of the meso‐tartrate are coordinated in the Ni‐meso‐tartrate complex. The second carboxylate group is also coordinated in the Ni‐malate complex. The rate determining step for the formation of the chelate is the closing of the ring and not the formation of the first bond.A second relaxation time that is observed in Ni‐D‐tartrate can be explained by assuming a dimerisation reaction according to NiL + NiL → Ni2L2. A structure for the