Complexes of general formulation [Cr(Schiff-base)(H 2 0)2 ] X, where Schiff-base = 1, 2-bis(saticylideneamino)ethane (salen), 1, 3-bis(salicylideneamino) propane (salprn) and 1, 4-bis(salicylideneamino)butane (salbuen) and X = CIO, or CI have been prepared and characterised. Single-crystal structure of the complex trans[Cr(salprn)(H20)2]C1 has been resolved. Evidence for less distorted coordination geometry around chromium in the salprn analogue as compared to that in trans-[Cr(salen)(H20)2] ÷ has been presented. The kinetics of the aqua ligand substitution in the complexes Cr(Schiff-base)(HzO)~-by thiocyanate have been investigated under pseudo-first order conditions with [NCS-]>>[Cr(III)], T= 10-50°C, [H ÷ ] = 10 -8-10-1 M, I = 1"0 M (LiC10,). An attempt has been made to discuss the anomalous lability of trans-[Cr(salen)(H20)2] ÷ reported earlier in comparison to the reactivities of salprn and salbuen analogues. Bimolecular rate constants for the aqua ligand substitution by NCS-in [Cr(Schiffbase)(H2 0)2 ] ÷ at 25°C vary by more than two orders of magnitude depending on the nature of the Schiff-base ligand. The reactivity order is discussed in terms of the possible steric strain imposed by the equatorially coordinated quadridentate ligand.