Dependence of the Distortion of the Square Pyramids in A^jV-Dimethylethylenediammonium Pentachloroantimonate(III) on the Geometry of Hydrogen Bonds

Z. Naturforsch. 56 b, 521-525 (2001); received March 12, 2001 /V,/V-Dimethylethylenediammonium Cation, Chloroantimonate(III) /V,/V-Dimethylethylenediammonium pentachloroantimonate(III) crystallizes in the mono­ clinic system, in space group P2i/c (a = 12.460(2), b = 10.252(2), c = 10.330(2) A, ß = 97.75(3)°, V = 1307.5(4) Ä3, Z = 4, dc = 1.997, dm = 1.99(2) g/cm3). The crys­ tal structure of [(CH3)2NH(CH2)2NH3][SbCl5j consists of isolated [SbCls]2 anions and [(CH3)2NH(CH2)2NH3r cations. The [SbCls] anion has a distorted square pyramidal ge­ ometry, 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)2NH(CH2)2NH3]2+ cations. The five non-equivalent Sb-Cl bond distances within the [SbCls]2square pyramid are significantly different. The equatorial Sb-Cl bonds are in the range 2.427(2)-2.968(2) Ä, whereas the axial one is 2.384(1) A long. The study reveals that N-H...C1 hydrogen bonds are responsible for the deformation of equa­ torial Sb-Cl bonds from the mean value of 2.654(7) A. Analysis of intermolecular interactions between the [SbCls]2pyramids in the structure, reflected in changes of Sb-Cl bond lengths from the values characteristic of non-interacting pyramids, leads to the conclusion that the van der Waals radius of Sb is significantly smaller than that estimated by Pauling.