Liaisons hydrogène et coordination du calcium dans les cristaux de CaCl₂.4H₂Oα

Abstract

The crystal structure of tt-CaC12.4H20 was redetermined from three-dimensional X-ray data collected by a Nonius CAD-4 diffractometer with Mo Kc~ radiation. The compound crystallizes in the triclinic space group P1 with two formula units in the cell. Cell dimensions are a = 6.5932 (6), b = 6.3673 (8), c = 8.5606 (15) A, a= 97.83(1),fl= 93.50(1), 7= 110.58(1) ° , V= 331.02 A 3. The H atoms were located by difference syntheses. After least-squares refinement R = 0.033, R w = 0.038. The Ca coordination is seven and not six as considered in previous work. The structure consists of [CaC12.4H20] 2 units held together by hydrogen bonds.

Vibrational and reorientational dynamics, crystal structure and solid–solid phase transition studies in [Ca(H2O)6]Cl2 supported by theoretical (DFT) calculations

“…Close inspection of the results showed that experimental pattern fits to [Ca(H 2 O) 4 ]Cl 2 . The theoretical patterns were generated with the use of the Fullprof package based on crystal structures data determined by us from X‐ray single‐crystal diffractions for [Ca(H 2 O) 6 ]Cl 2 and based on data available in the literature for [Ca(H 2 O) 4 ]Cl 2 and [Ca(H 2 O) 2 ]Cl 2 . To put it simply, during the measurements, the vacuum in the cryostat caused that [Ca(H 2 O) 6 ]Cl 2 lost two out of six H 2 O molecules despite the sample being closed in an Al envelope.…”

“…. The initial unit cell optimised in CASTEP periodic boundary condition calculations for [Ca(H 2 O) 2 ]Cl 2 and [Ca(H 2 O) 4 ]Cl 2 compounds was constructed based on the X‐ray single‐crystal diffraction data, respectively (Fig. S6 in the Supporting Information).…”

Neutron diffraction studies of polyiodides. III. Calcium decaiodide heptahydrate

“…Of these, only nine examples are of a metal ion coordinated to seven equivalent ligands but these do not include an ion coordinated to seven water molecules. Ca does, however, occur in a seven-coordinated state in Ca(C4H304)2.5H20 (Hsu & Schlemper, 1978), CaC12.4H20 (Leclaire & Borel, 1979), and CaVaO 7 (Bouloux & Galy, 1973).…”

La forme γ du dichlorure de calcium tétrahydraté

“…Apr6s avoir determin6 la structure de la forme fl (Leclaire & Borel, 1978) et complet6 celle de la forme stable - (Leclaire & Borel, 1979), nous avons entrepris I'&ude de la forme instable 7 du dichlorure de calcium t&rahydrat& Les cristaux ont 6t+ obtenus en laissant refroidir lentement jusqu'& 298 K, une solution obtenue par dissolution fi chaud de 52 g de CaCI 2 dans 48 g d'eau (Bassett et al, 1933).…”

“…La forme des cristaux obtenus correspond & celle d~crite par Shepelev, Lyashenko & Druzhinin (1950) (10) 170 (9) 3,2 (1,1) H (12) 407 (14) -220 (11) 14 (10) 3,6 (1,3) H (21) 96 (13) 57 (10) 334 (9) 3,1 (1,1) H (22) - 103 (16) -.-37 (12) 302 (11) 4,3 (1,5) A GNOSTC (Coppens, Leiserowitz & Rabinovich, 1965: de Meulenaer & Tompa, 1965 (Leclaire & Borel, 1979) et Ca(NO3)2.4H20. (Leclaire & Monier, 1977) (12) CP ~ 0.97 (10) 3.197(3) 2,25(10) 166 (7) O12) 11(21) CP t~ 0,82 (7) 3.206 (3) 2,40 (7) 167 (7) 105 (8) O (2) (Fig.…”