Anion symmetry

Salt Anion symmetry Transition temperature T (K) Wave vector" Unit cell References... 

Another interesting observation is that alkyl substitution causes a substantial decrease in the lifetime of benzene anions ( ). We believe that this is due to the presence of the = 1 and 1=2 partial waves in the charge density of the LUMO of the alkylbenzenes. The benzene anion symmetry) itself has a leading partial wave of = 3. 

Carbonyl metalates of alkali metals have been studied in solution by IR spectroscopy (see Section 5). Considerable ion pairing occurs with consequent lowering of the anion symmetry, as evidenced by the appearance of more bands than expected in the 1900 1700 cm region. The alkali metal cation is assumed to establish an ion dipole interaction with the carbonyl oxygens. 

Ionic oxysalts are the most stable. Where anionic-cationic interactions introduce some covalent character, the decrease in anionic symmetry is accompanied by a marked decrease in stability. Transition metal perchlorates, and perchloric acid, tend to be explosives with unpredictable and often dangerous properties. 

CeOi2 icosahedron. The set of ideal oxygen positions has very nearly icosahedral symmetry, but because of the presence of the Mo atoms and the marked distortion of each octahedron (23) the true anion symmetry is Tft. Isomorphous anions containing Th(IV) (130) and U(IV) (131) are known and the existence of anions containing Pr(IV), Np(IV), Pu(IV), and Am(IV) has been predicted (131). An unstable 12-molybdostannate-(IV) anion (121) of unknown structure has never been re-examined. 

Rode has calculated the electronic structures for two monomeric forms of IO2F3, with C2V (trigonal bipyramidal) and Cj (tetragonal pyramidal) symmetry. He reports that the C2 isomer is strongly favoured. Aubke et have reported the preparation of CsF,I02F3 and I02F3,SbFs. The Raman spectra of these new compounds have been interpreted in terms of an ionic formulation for Cs IO2F4, with C2V, cis-octahedral anion symmetry, and of an O-donor interaction in the SbFs adduct. 

The vibrational frequencies of some crystalline perteehnetates arc listed in the following tables. The factor group symmetry is Q/ the anion symmetry is I, /. 

The anions of the MY type are involved in the formation of hydrogen bonds with the acidic hydrogens of the ammonium- and hydroxonium-type cations The interaction of anions with the cationic part of the arenium ion salts results in decreasing the anion symmetry to be recognized by the splitting of the AICI4 lines in the Raman spectrum of the mesitylenium tetrachloroaluminate. 

The fivefold symmetry of this anion is completed by the linkage of five PWe groups and the central sodium ion lies in the center of a plane defined by the oxygen atoms of the phosphate groups. It appears that the kinetically inert (on the NMR timescale) sodium ion is essential for the construction of the cluster. The presence of the sodium cation reduces the overall anion symmetry from Dsh to Csv The P5W30 anion is even more robust than the PgW48 one (pH stability range ->0 10). Under hydrothermal conditions the central Na+ can be replaced by other cations of similar size, e.g., most Ln , and Reduction of Eu to Eu in these... 

The lattice symmetry is directly influenced by the complex anion symmetry. Generally, the structure can derive from simple structures considering the deformation of the symmetry as a result of the orientation of the complex anion in relation to the symmetry elements of the lattice. 

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