The four electron-transfer complexes trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))nickel, trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))copper, trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))palladium and trans-(di(N,N-diethyl-(2-phenyldiazenyl)thioformamide-kappaS,kappaN2))platinum have been crystallized, and their structures have been determined at low temperature. All the complexes are of the M-N2S2 type. The crystals of both the nickel and the copper complex belong to the tetragonal P4(1)2(1)2 system, in which the central metal ion lies on a twofold axis. The tetrahedral molecular symmetry around the central metal ion is unusual for the M-N2S2 electron-transfer complexes. The crystals of the palladium and platinum complexes on the other hand belong to the monoclinic C2/c system in which the metal ion lies on an inversion centre. The molecular symmetry around these metal ions is square planar. It is demonstrated that the pi electron density in the ligand planes has a high degree of delocalization. Furthermore, unusually large line broadening of the 1H NMR spectra was observed and investigated as a function of temperature for the palladium complex.