The kinetics of axial ligation by pyridine of Ch3Rh(DH)2H2O and the reverse hydrolysis reactions were studied in aquaeous solution as a function of pH. The kinetic data indicate that the lability of this complex is strongly influenced by the extent of protonation of the equatorial chelating ring, both the doubly protonated Ch3Rh(DH2)(DH)L+ and the deprotonated Ch3Rh(DH2)(DH)L− species being more reactive than the species Ch3Rh(DH)2L, containing intact intramolecular hydrogen bonds. A comparison is made with the behaviour of the analogous Co(III) complexes.