Study of acidic (tetracaprolactam) dodecamolybdosilicate of the composition (C<sub>6</sub>H<sub>11</sub>NO)<sub>4.5</sub>Н<sub>4</sub>[SiМо<sub>12</sub>O<sub>40</sub>]
New caprolactam dodecamolybdosilicate of the composition (C<sub>6</sub>H<sub>11</sub>NO)<sub>4.5</sub>Н<sub>4</sub> [SiМо<sub>12</sub>O<sub>40</sub>] (I) is synthesized. Chemical and crystallographic analyses, NMR and IR spectroscopic studies are performed. Compound I is found to crystallize in the monoclinic system with the space group P 2<sub>1</sub>/ n. Unit cell parameters are: a = 19.945(4), b = 13.340(3), c = 28.110(6) Å, b = 110.75(3)°, r<sub>calc</sub> = 2.232 g/cm<sup>3</sup>, М = 2350.63, Z = 4, V = 6994(3) Å<sup>3</sup>.