A new series of heterodinuclear nickel(II) -zinc(II) complexes, [NiL (.) ZnCl2.4-picoline] (1), [NiLDM (.) ZnCl2.4-picoline] (2), [NiL ZnBr2.4-picoline] (3), [NiLDM-ZnBr2.4-picoline] (4), [NiLDM-ZnBr2.3-picoline] (5), [NiLDM (.) ZnBr(2)(.)3,5-lutidine] (6) and [NiL. ZnI2.4-picoline] (7), where L is, N,N'-bis(salicylidene)-1,3-diaminopropane dianion and LDM is N,N'-bis(salicylidene)-2,2'dimethyl-1,3-diaminopropane dianion, were prepared. The complexes were characterized by elemental analysis, thermogravimetric analysis and IR spectroscopy. X-ray crystallographic analysis of complexes 1, 2 and 4 revealed that nickel(II) ion in heteronuclear complexes had a square-pyramidal coordination sphere. It is concluded that formation of square-pyramidal nickel(II) coordination depends strongly on the concentration of methyl pyridine present in the medium and occurs when methyl pyridine/Ni ratio is below 1.5. (C) 2002 Elsevier Science B.V. All rights reserved.