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The crystallographic analysis of the structure of three inorganic compounds with Lindqvist polyanions establishes that their structural arrangement is determined by the geometry and symmetry of the [M6] cation octahedron by the coherent assembly of [M6O19] building blocks. The relative stability of the structures is estimated from the number of degrees of freedom of their atoms and the fundamental volumes characterizing the degree of symmetrization of the structures.

The structure and relative stability of 1,4-dioxane-water, (Diox)n·(H2O )m (n = 1, 2, m = 1–6), molecular complexes have been calculated by semiempirical MNDO/PM3 method. A considerable variety of (Diox)n·(H2O )m isomeric structures was stated. The mean energy of ODiox…HW-OW hydrogen bond in (Diox)n·(H2O)m complexes formed by 1,4-dioxane molecules in the chair conformation amounts to −2.293 ± 0.210 kcal/mol with the average bond length 2.797 0.015 A.

Potential interaction surface of polyhydrated monomethyl mercury cation with inorganic ligands (X = Cl, Br, I, HO, HS, HSe) has been studied by quantum chemical methods. Thermodynamic and kinetic parameters of complexation processes were determined. A relative stability of polyhydrated complexes (Me-Hg—X) to the dissociation of coordination bond Hg—X was found to increase in the series: HO ≪ I < Br < HS < HSe < Cl.

The structure and the relative stability of the N-, Cα-, and Cβ-anions of pyrrole, its mono- and dimethyl derivatives, and their adducts with carbon disulfide were studied by the ab initio method (MP2/6-31+G*//RHF/6-31+G*). The substituent effect on the reaction path is considered. For unsubstituted pyrrole, the stability of the adducts decreases in the series Cα > N > Cβ. The stability of the N-adducts decreases considerably in the presence of the methyl groups introduced into the α-position in view of steric interactions. Possible reasons for the experimentally observed formation of the thermodynamically less stable N-adduct of the unsubstituted pyrrole and for the absence of N-adducts in reactions of the methyl derivatives with CS2 are discussed.

The crystal structures of mercury oxosalts are described with isolation of oxocentered tetrahedrul groups [OHg4]. The bond topology of the oxocentered polycations is more diversified and rich than the motifs of canonic polyhedra in “classical” crystal chemistry and often is a more striking illustration of the unique nature of the structure of compounds from this class. The relative stability of the oxocentered polyions indicates that they play an important role in structure formation and possibly exist in various natuml media, making it appropriate to consider these groups in analysis of mercury transfer processes occurring in nature. The oxocentered approach proved to be useful for establishing structure-property type correlations and promotes the understanding and predicting the anisotropy of physical properties.

Stabilization of cyclic mercury clusters is discussed using the MNDO method. The bonding character of the highest occupied molecular orbital is shown to be one of the essential criteria of the relative stability of these systems. This criterion max be satisfied by structures with both direct and indirect (via the bridging chlorine atoms) bonding of mercury atoms.

The problem of stabilizing the linear clusters of mercury by terminal groups is discussed in terms of the MNDO method for the following model and real compounds: Hgn (I), HgnCl2 (II) and Hgn(AlCl4)2 (III) with n=2–4. It is shown that the terminal acceptor groups stabilize the linear mercury chains. It is established that in systems (II) and (III), unlike in (I), the highest occupied molecular orbitals are bonding.

Various cross-sections of the potential energy surfaces (PES) of intramolecular rearrangements in LiBH2, LiAlH2, LiCH2+, and LiSiH2+ in the lowest singlet states were calculated in the SCF/3–21G approximation. The geometric parameters of special points on the PES were refined on the SCF/3–21G* level and their relative energies were refined in the framework of the MP3/TEHD+PP approximation. The form of the PES is significantly altered both upon going from Period 2 compounds to Period 3 compounds and with change in the charge of the system despite the isoelectronic nature of the compounds examined. Predictions are made for the change in the relative stability of the classical and bridged isomers (LMX2 and L(X)2M) in monotypic systems upon change in the cations L+ and substituents X in various series.

1. Solubility in the systems NH4NO3−NH4I−H2O and KNO3−KI−H2O at 25° was studied. 2. Solubility in the systems named was compared with the structures of the component salts and their saturated solutions. 3. The varying solubility of salts in the studied systems is determined to a certain degree by the relative stability of the ionic close order taking part in the crystallization of salts from saturated solutions: the more stable this order is, the less soluble is the salt. 4. Joint solubility in both systems is characterized by a linear relation between xo−x (moles of salted-out salt) andy (moles of dissolved salt). 5. The linear relation between xo−x andy, its representation for KNO3 by two straight lines of different slope, and the difference in displacement coefficients indicate with one accord, that joint solubility is determined by the structural state of saturated solutions.