The crystals of the title compounds (H3O)(C3H5N2)[Mn(OH)(6)Mo6O18](.)3.5H(2)O 1 and (H3O)(3)[Co(OH)(6)Mo6O18](.)7H(2)O 2 have been prepared and structurally determined by X-ray single-crystal diffraction. Compound, 1 crystallizes in monoclinic, space group C2/c with a = 21.5018(9), b = 10.9331(5), c = 11.8667(5) Angstrom, beta = 95.3570(10)degrees, V = 2777.5(2) Angstrom(3), Z = 4, D-c = 2.802 g/cm(3), M-r = 1171.80, mu(MoKalpha) = 3.173 mm(-1), F(000) = 223, the final R = 0.0458 and wR = 0.1041 for 2093 observed reflections (I > 2alpha(I)); Compound 2 crystallizes in monoclinic, space group P2(1)/c with a = 11.4042(12), b = 10.9481(11), c = 11.6722(12) Angstrom, beta = 99.948(2)degrees, V = 1435.4(3) Angstrom(3), Z = 2, D-c = 2.794 g/cm(3), M-r = 1207.80, mu(MoKalpha) = 3.223 mm(-1), F(000) = 1160, the final R = 0.0544 and wR = 0.1066 for 1906 observed reflections (I > 2sigma(I)). Both compounds 1 and 2 adopt the Anderson structure, in which the anion is of centrosymmetry and formed by six octahedral edge-sharing MoO6 units surrounding the central MO6 (M = Mn or Co) octahedron.