Study of the molecular and crystal structure of a new coordination polymer of copper(II) nitrate with 4,4,10,10-tetramethyl-1,3,7,9-tetraazospiro[5.5]undecane-2,8-dione

A coordination polymer {[Cu(C₁₁H₂₀N₄O₂)₂(H₂O)]²⁺·2(NO ₃ ^? )} _n (I) is synthesized and analyzed using single-crystal XRD. The crystals are monoclinic: space group P2/c, a = 12.5237(6) Å, b = 7.3310(3) Å, c = 16.8926(8) Å, β = 92.569(4)°, V = 1549.38(13) ų, ρ_calc = 1.47 g/cm³, and Z = 2. The copper atom is in a special position in the second-order axis. The coordination polyhedron of the metal is a trigonal bipyramid. In the axial direction, it is coordinated by two oxygen atoms O(1) of the organic ligand molecules connected by the symmetry operation [?x, y, 0.5-z]; the angle O(1)Cu(1)O(1) ⁱ is 175.16(15)°. In the equatorial direction, the copper atom is coordinated by oxygen atoms O(2) of two ligand molecules connected with the reference molecule by the symmetry operations [?x, y, 0.5-z] and [x, 1-y, ?0.5+z] and the water molecule O(6) in a special position on the twofold axis. The OCuO angles between the equatorial oxygen atoms are 96.80(16)–131.60(8)°, and those between the axial and equatorial atoms are 87.58(8)-91.60(10)°. It is noteworthy that the length of the Cu-O(1) bond (1.955(2) Å) with the axial carbonyl oxygen atom is somewhat shorter than the bond (2.060(3) Å) with the equatorial atom. Nitrate anions are outside the coordination sphere of the metal. The Cu…Cu distance in the polymer is 8.33 Å. To confirm the purity of the sample of I, the powder X-ray pattern is refined by the Rietveld method; the lattice parameters at room temperature are: a = 12.535(4) Å, b = 7.3161(13) Å, c = 16.841(5) Å, β = 92.11(2)°, and V = 1543.4(7) ų.