The cobalt(II) and nickel(II) nitrate complexes with an island structure (Na{sub 2}[Co(NO{sub 3}){sub 4}] (I) and K{sub 2}[Co(NO{sub 3}){sub 4}] (II)] and a chain structure [Ag[Co(NO{sub 3}){sub 3}] (III) and K{sub 2}[Ni(NO{sub 3}){sub 4}] (IV)] are synthesized and investigated using X-ray diffraction. In the anionic complex [Co(NO{sub 3}){sub 4}]{sup 2-} of the crystal structure of compound I, the Co coordination polyhedron is a twisted tetragonal prism formed by the O atoms of four asymmetric bidentate nitrate groups. In the anion [Co(NO{sub 3}){sub 4}]{sup 2-} of the crystal structure of compound II, one of the four NO{sub 3} groups is monodentate and the other NO{sub 3} groups are bidentate (the coordination number of the cobalt atom is equal to seven, and the cobalt coordination polyhedron is a monocapped trigonal prism). The crystal structures of compounds III and IV contain infinite chains of the compositions [Co(NO{sub 3}){sub 2}(NO{sub 3}){sub 2/2}]{sup -} and [Ni(NO{sub 3}){sub 3}(NO{sub 3}){sub 2/2}]{sup 2-}, respectively. In the crystal structure of compound III, seven oxygen atoms of one monodentate and three bidentate nitrate groups form a dodecahedron with an unoccupied vertex of the A type around the Co atom. In the crystal structure of compound IV, the octahedral polyhedronmore » of the Ni atom is formed by five nitrate groups, one of which is terminal bidentate. The data on the structure of Co(II) coordination polyhedra in the known nitratocobaltates are generalized.« less