Abstract
Caesium propano-ate monohydrate, Cs+·C3H5O2 -·H2O, is composed of two symmetry-independent Cs+ cations, which are situated on the special position 4e of space group P 21 m, one symmetry-independent propano-ate mol-ecule in a general position and a pair of water mol-ecules also situated on special position 4e. Two pairs of these symmetry-independent cations, four propano-ate mol-ecules and two pairs of symmetry-independent water mol-ecules form a repeat unit. These units form columns that are directed along the c axis and possess symmetry mm2. There are four such columns passing through each unit cell. Each column is inter-connected to its neighbours by four bifurcated three-centred Ow-H⋯Op (w = water, p = propano-ate) hydrogen bonds of moderate strength. There are also four intra-molecular Ow-H⋯Op hydrogen bonds of moderate strength within each column. One Cs+ cation is coordinated by six oxygen atoms (two water and four carboxyl-ate) in a trigonal-prismatic geometry, while the other Cs+ cation is coordinated by four water and four carboxyl-ate O atoms in a tetra-gonal-prismatic arrangement.
Highlights
No structure of a simple hydrated alkali propanoate has been determined until now. (‘Simple’ means a structure where the constituting cation belongs just to one chemical species.) This is in contrast to alkali formates and acetates where water-free alkali salts and complexes with parent acids as well as hydrates are known
The structural differences between alkali formates and acetates on one hand and simple alkali propanoates such as Li(C3H5O2) (Martınez Casado et al, 2009) and M(C3H5O2); M = Na, K, Rb, Cs (Fabry & Samolova, 2020) on the other reflect the chemical differences between these two groups of compounds. The latter structures are characterized by stacking of layers that are composed of a metal–oxygen bilayer surrounded by hydrophobic layers comprising the ethyl groups
Mirnaya et al (1991) pointed out the tendency for various alkanoates to form hydrates. Such a case is reported in this study – see the Synthesis and crystallization section. It is of interest how strikingly different the title structure Cs(C3H5O2)ÁH2O is from Cs(C3H5O2) (Fabry & Samolova, 2020), despite the chemical similarity
Summary
No structure of a simple hydrated alkali propanoate has been determined until now. (‘Simple’ means a structure where the constituting cation belongs just to one chemical species.) This is in contrast to alkali formates and acetates where water-free alkali salts and complexes with parent acids as well as hydrates are known. The structural differences between alkali formates and acetates on one hand and simple alkali propanoates such as Li(C3H5O2) (Martınez Casado et al, 2009) and M(C3H5O2); M = Na, K, Rb, Cs (Fabry & Samolova , 2020) on the other reflect the chemical differences between these two groups of compounds. The latter structures are characterized by stacking of layers that are composed of a metal–oxygen bilayer surrounded by hydrophobic layers comprising the ethyl groups. It is of interest how strikingly different the title structure Cs(C3H5O2)ÁH2O is from Cs(C3H5O2) (Fabry & Samolova , 2020), despite the chemical similarity
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