Hexavalent tungsten complexes were synthesized using ethylenediaminetetraacetic acid (EDTA) having the general formula A4 [W2O6Y].xH2O (where A is Na+ and/or K+ and/or NH4+, Y is C10H12N2O8 and x = 2,4 or 8). The goal of the study of these complexes was the verification of the interference of cations with different sizes in the physical-chemical properties of these complexes and the comparison of the obtained results for tungsten (VI) complexes + EDTA with the molibdenum (VI) complexes + EDTA. Elementary analysis, atomic absorption, thermogravimetric analysis, conductimetric analysis and X-ray power diffraction were used to characterize the complexes. It was concluded that the size of the cations did not interfere with the thermal stability nor with crystallization of these complexes. All the complexes crystallized in monoclinic systems and showed similar lattice parameters.