The crystal and molecular structures of two isostructural complexes: [(H₃O•18-crown-6)₂(ZnCl₄)] and [(H₃O•18-crown-6)₂(MnCl₄)]

Abstract

. Can. J. Chem. 68, 797 (1990) New macrocycle polyether 18-crown-6 complexes of stoichiometry [(H30+. 1 8 -~r o w n -6 )~(~C l~~-) ] have been synthesized for M = Zn and Mn. The two complexes are isostructural and crystallize in the monoclinic system, space group C2/c. The unit cell dimensions are as follows: a = 16.229(9), b = 11.535(3), c = 20.134(8) A, P = 97.55(4)" and a = 16.255(6), b = 11.625(3), c = 20.122(8) A, P = 96.54(3)" for the Zn and Mn complexes respectively. In both crystal structures (final R,, = 0.048 with 1817 reflections for Zn and R, = 0.074 with 728 reflections for Mn), the crown ether molecule and the H30+ cation to which it is hydrogen-bonded are disordered over two sites. The M C~~~-anions, which have tetrahedral toordination, are on crystallographic twofold axes of rotation. The Mn-Cl and Zn-C1 distances average 2.270 and 2.361 A respectively. The hydronium cation, H30+, has pyramidal coordination. Of the two disordered crown ether molecules in the Zn and the Mn complexes, one has a slightly deformed (ttg)6 conformation while the other one may be described as having the distorted (ttg)5(ttc) conformation. These observations are in agreement with the infrared analyses of the complexes.Key words: 18-crown-6 complexes, hydronium ion, ~n C l~~-, M~c I~~-, crystal structure. pyramidale. Des deux molCcules dlCthers couronnes dtsordonnCes qui sont prksentes dans les complexes du Zn et du Mn, l'une posskde une conformation 1Cgkrement dCformCe (ttg)6 alors que l'on peut dtcrire la conformation dCformCe de l'autre par ( t~)~( t t c ) .Ces observations sont en accord avec les analyses infrarouges de ces complexes. Mots clis : complexes 18-couronne-6, ion hydronium, znC14'-, MnC142-, structure cristalline.[Traduit par la revue]

Crown ethers as stabilising ligands for oxonium ions

“…In many of the complexes discussed above, oxonium ions have been found to crystallise from toluene, in which the liquid clathrate effect [51][52][53] as been observed. Also involved in a number of these species, 31,34,35,39,40,[43][44][45][46][47][48][49] are transition metals which have potentially catalytic properties, so the possibility of studying catalysis in liquid clathrate media is an exciting prospect. The highly ionic medium and the potential for a simple separation mechanism 52,53 could have great merit.…”

Structural-chemical aspects of complexation in metal halide–macrocyclic polyether systems

“…Its formation can only be attributed to partial hydrolysis in the solution or to the use of the reagents containing water. 33 The oxonium ion in 34 is located in the centre of the cavity of the CE molecule. In the nearly regular tetrahedral anion, the Mn ± Cl distances vary from 2.35 to 2.37 # A. Interestingly, hydrolysis products were not detected in the analogous reaction performed in the presence of an excess of water.…”

Synthesis and crystal structural characterization of an unsymmetric neodymium(III) cryptate

“…26, 27 Although the Nd III ion in our complex is paramagnetic, the 1 H NMR spectrum shows a broad signal characteristic of the oxonium ion in the range δ 10-11, which is in agreement with that of analogous oxonium complexes. 28, 29 The other proton has been located on the water molecule from the Fourier-difference map. In the inner sphere of lanthanide macrocyclic complexes, the water molecule usually co-ordinates to the central lanthanide ion, thus decreasing its luminescence efficiency.…”