Starting from 4,5-(ethylenedithio)-1,3-dithiol-2-one and 1,3-dithiol-2-one the disodium 5,6-dihydro-1,4-dithiin-2,3- dithiolate (Na2dddt) and disodium 1,2-dithiolate (Na2edt) salts were prepared, which react with NiCl2 in air to give the complex Ni(dddt)(edt) (3ab). This compound was characterized analytically and spectroscopically. The method is applicable for the preparation of similar unsymmetrical complexes.