The crystal structure of cupric formate tetrahydrate, Cu(HCO2)2.4H2O

Abstract

The crystal structure of this compound has been determined by Patterson and Fourier syntheses and refined by Fo-Fc syntheses. Each copper atom is surrounded by four oxygen atoms of four different formate ions in an approximately square configuration and by two water molecules at a greater distance. The formate ion is nearly symmetrical with an O-C-O angle of 120 ° .In the course of our investigations on paramagnetic resonance absorption, it became desirable to know the atomic arrangements of the crystals of cupric formate tetra-and di-hydrates. The present note reports the structure analysis of the former carried out by us recently. Kabraji (1931) has already given the cell dimensions, the number of formula units and the space group.Useful X-ray data in the present experiments were obtained from oscillation photographs taken with Cu K~ radiation (4 = 1.542/~): The unit cell, containing two formula units, has the dimensions a = 8-18±0-02, b = 8.15±0.02, c = 6.35±0.02 J~, = 101 ° 5'±20', which almost agree with Kabraji's data, the morphological value of fl being taken. From the systematic absences, the space group was found to be P2i/a-C~h (not C2z/m-C~h as reported by Kabraji); The intensities of the reflexions were estimated visually and corrected for Lorentz and polarization factors. In view of the small size of the crystals used, absorption and extinction corrections were neglected. Because the general point position in P2z/a is fourfold, and since the unit cell contains only two formula units, it follows that the copper atoms must occupy special positions.From the ordinary Patterson maps projected along three crystallographic axes, approximate parameters for the O~, On, ~ and Ozv atoms could be determined, while those for the C atoms remained less certain. Next, the electron-density maps projected along the c and b axes were prepared by taking into account probable positions of the C atoms. The atomic parameters were refined by two-dimensional Fourier syntheses and structure-factor calculations Table 2.* The R factors are 0.10, 0.12 and 0.11 for (h/c0), (hO1) and (Ok/), respectively, when the absent and over-exposed spectra are excluded.

Synthesis and Crystal Structure of CuC4O4·2 H2O

“…They are as short as bond lengths observed in Cu -OH bonds. Jaggi and Oswald [7] found short Cu -OH distances of 193 and 194 pm in Cu(OH)2, and Subrata Ghose and Fehlmann [8] re ported Cu-OH bond lengths in the range from 189.4 to 194.9 pm in clinoclas (Cu3A s0 4(0 H )3), whereas Cu -H20 distances should have greater values like the 236 pm found in Cu(HCOO)2-4 H20 [9]. In NiC40 4(C3N2H4)4(H20 )2 [2] the N i-H 20 dis tance is 206.9 pm, whereas the Ni -Osquarate bond length is 212.1 pm.…”

Comment on three proposed hydrate structures

“…The space group P212121 and cell dimensions are said to be the same as those determined by Nitta (1928) (Kiriyama, Ibamoto & Matsuo, 1954) carbonoxygen distances in the formate group were found to be 1.26 and 1.25 A. Third, the oxygen neighbors of strontium do not produce a satisfactory coordination polyhedron.…”

The crystal and molecular structure of bis(hydrogen o-phthalato)diaquocopper(II)

“…A strong intramolecular hydrogen bond, O(2)H... 0(3)=2.422(6)A, determines the relative orientations of the carboxyl groups which are, for this reason, unable to act as bridges between adjacent metal atoms, as observed in other CuU-carboxylate complexes, e.g. Cu II acetate dihydrate (van Niekerk & Schoening, 1953), Cu L1 formate tetrahydrate (Kiriyama, Ibamoto & Matsuo, 1954) and Cu u benzoate trihydrate (Koizumi, Osaki & Watanabd, 1963). The same kind of behaviour is observed in Cu u salicylate tetrahydrate (Hanic & Michalov, 1960) in which the OH group is hydrogen-bonded to the carboxyl oxygen atom involved in the long bond with the metal atom.…”