Chelation of the tetradentate pyridyl di-Schiff-base ligands, N,N′-bis-(1-pyridin-2-yl-ethylidene)-propane-1,3-diamine (L1) or N,N′-bis-(1-pyridin-2-yl-ethylidene)-ethane-1,2-diamine (L2) to a cadmium(II) centre reveals interesting structural deviations from regular octahedral geometry in the resulting hexacoordinated complexes [Cd(L 1)(NCS)2] (1) and [Cd(L2)(NCS)2] (2), respectively. The two tetradentate ligands L1 and L2 differ only in the polymethylene chain - (CH2)3 and (CH2)2, respectively, which connects the two halves of the symmetric ligands. Complex 1 assumes a trigonal prismatic (TP) geometry. The structure of 2 reveals a severely distorted octahedral geometry. The structural differences between [Cd(L1)(NCS)2] (1) and [Cd(L 2)(NCS)2] (2) can be traced to the length of the polymethylene spacers and the formation of a six- versus a five-membered metal-chelate ring together with the pyramidal Cd(L1) and planar Cd(L2) arrangement. © 2005 Elsevier Ltd. All rights reserved.