Dependence of the distortion of the square pyramids in N,N-dimethylethylenediammonium pentachloroantimonate(III) on the geometry of hydrogen bonds

N,N-Dimethylethylenediammonium pentachloroantimonate(III) crystallizes in t he monoclinic system, in space group P2(1)/c (a = 12.460(2), b = 10.252(2), c 10.330(2) Angstrom, p = 97.75(3)degrees, V = 1307.5(4) Angstrom (3) Z = 4, d(c) = 1.997, d(m) = 1.99(2) g/cm(3)). The crys tal structure of [(CH3)( 2)NH(CH2)(2)NH3] [SbCl5] consists of isolated [SbCl5](2-) anions and [(CH3) (2)NH(CH2)(2)NH3](2+) cations. The [SbCl5](2-) anion has a distorted square pyramidal geometry, presenting one short axial and four long equatorial Sb -Cl bonds. The square pyramids are characteristically stacked one close to the other, parallel to the c axis. The voids between the anionic sublattice are filled by [(CH3)(2)NH(CH2)(2)NH3](2+) cations. The five non-equivalent Sb-Cl bond distances within the [SbCl5](2-) square pyramid are significant ly different. The equatorial Sb-Cl bonds are in the range 2.427(2)-2.968(2) Angstrom, whereas the axial one is 2.384(1)Angstrom long. The study reveal s that N-H . . . Cl hydrogen bonds are responsible for the deformation of e quatorial Sb-Cl bonds from the mean value of 2.654(7) Angstrom. Analysis of intermolecular interactions between the [SbCl5](2-) pyramids in the struct ure, reflected in changes of Sb-Cl bond lengths from the values characteris tic of non-interacting pyramids, leads to the conclusion that the van der W aals radius of Sb is significantly smaller than that estimated by Pauling.