Polyoxometalates (POMs) are attractive for the design of new materials, due to diverse chemistry and favorable structural and electronic properties. Tungstates-containing polyoxometalates have become the object of interest in optoelectronics due to their putative electro-, photo-, and thermochromism, and potential applications as solid nanocomposite molecular devices. The design of polyoxometalate materials with targeted threedimensional structures has recently emerged as an active research area. Despite a number of successful efforts, much experimental and theoretical work remains before this can become a general approach. The single-crystals of title compound of general formula KNa2(C12H24O6)3(H3O)[H2W12CoO40]×1.5H2O were obtained by synthetic procedure described in [1]. The crystal structure of I has been determined by single-crystal X-ray method and proved the chemical structural formula [K(1)(18-Crown6)(H2O)]1+ [Na(1) (18-Crown-6)]1+ [Na(2) (18Crown-6)]1+ 0.5 [Na(3) (18-Crown-6) (H2O)]1+ 0.5[H3O]1+ [H2W12CoO40]4-. Compound crystallizes in triclinic space group P-1 (No.2), a= 12.8790(5) Å, b = 14.7390(7) Å, c = 22.7730(11) Å, a = 103.406(2)°, b = 101.219(3)°, g = 102.067(3) °, V=3975.7(3) Å3. The final R factor is 0.0723 for 11372 (Rint=0.1199) unique reflections and 1028 parameters. The structural analysis reveals that the crystals are build up from the Keggin-type [H2W12CoO40]4- polyoxoanions, [K(1) (18-Crown-6) (H2O)]1+, [Na(1) (18-Crown6)]1+, [Na(2) (18-Crown-6)]1+ 0.5, [Na(3) (18Crown-6) (H2O)]1+ 0.5, [H3O]1+ cations, and water molecules. In the polyoxoanion, the tungsten atoms exhibit a distorted {WO6} octahedral environment, with the W-O distances being within the 1.680(19)-2.260(16) Å range. The central Co(II)-atom is surrounded by four m4-O-atoms in a coordination geometry a distorted tetrahedron, with the Co - m4-O distances in the 1.897(18)1.938(16) Å range. The average W - m4-O bond lengths is 2.19(2) Å and very close to those described in the literature [2]. The [K(1) (18-Crown-6) (H2O)]1+ and [Na(1) (18-Crown-6)]1+ cations coordinate to polyoxoanion by means of the terminal oxygen atoms O(9T) and O(1T), K1-O= and Na1-O=. In the cation [Na(2)18C6]1+ 0.5 the Na(2) atom is disordered and occupied two positions. This work was supported by the RFFI - Moldova grant 08.820.08.035RF.figureFig. 1. A fragment of the crystal structure I.