[en] The specific features revealed in the structure of the d³ Cr(III), d² Cr(IV), d¹Cr(V), and d⁰ Cr(VI) peroxo complexes with the ratios M:O₂ = 1:1, 1:2, and 1:4 are considered. It is noted that, in eleven compounds of the general formula Cr(O₂)_nO_mA_p (n = 1, 2, 4; m = 0, 1; p = 0-4), the metal atoms can be in four oxidations states: +3 (d³), +4 (d⁴), +5 (d¹), and +6 (d⁰). This property distinguishes chromium peroxo compounds from molybdenum and tungsten dioxygen complexes, which, with one exception, are represented by the d⁰M(VI) compounds

[en] The specific features revealed in the structure of the molybdenum and tungsten peroxo complexes with the ratios M: O₂ = 1: 1, 1: 2, and 1: 4 are considered. It is demonstrated that the geometry of the coordination polyhedron of the metal atom is primarily determined by the 'metal: peroxo ligand' ratio. Formally, the pentagonal bipyramidal coordination polyhedra of the Mo(VI) and W(VI) oxo monoperoxo and oxo diperoxo complexes (the coordination numbers of the metal atoms are equal to seven) have different geometries, namely, the MO(O₂)A₄ pseudooctahedral and MO(O₂)₂A₂ pseudotrigonal bipyramidal configurations

[en] Specific structural features of mononuclear octahedral monooxo complexes of rhenium(V) with nitrogen atoms at the trans positions to the multiply bound oxo ligands are considered

[en] The specific structural features of technetium mononuclear octahedral oxo complexes have been considered. The structures of d²-Tc(V) mono- and dioxo complexes, d²-Tc(V) pseudodioxo compounds (Tc(V) mono-oxo complexes with an additional multiply bonded RO⁻ ligand), and d⁰-Tc(VII) trioxo compounds are analyzed.

[en] The crystal structure of (HPhen)₂S₂O₈ . 2H₂O is studied using X-ray diffraction. The crystals are monoclinic, a = 23.716(5) A, b = 10.220(2) A, c = 13.103(3) A, β = 128.03(2)^o, V = 2501.6(9) A³, Z = 4, space group C2/c, and R = 0.0745 for 1579 reflections with I > 2σ(I). The crystal is built of S₂O₈^2- centrosymmetric anions, HPhen⁺ cations, and molecules of crystallization water. Hydrogen bonds link the structural units into chains. Within a chain, stacking interactions are observed between the phenanthroline rings (the interplanar spacing between the rings is 3.8 A, and the dihedral angle between their planes is 8^o). The data of IR spectroscopy confirm the formation of the N(Phen)-H bond.

[en] The synthesis and X-ray diffraction study of three Ca[CuX(Nta)] . 2H₂O complexes, where X = Cl (I) or Br (II and III are the monoclinic and orthorhombic modifications, respectively), are performed. Structures I-III are built of [CuX(Nta)]^2- anionic complexes and hydrated Ca²⁺ cations, which are linked by Ca-O bonds into a three-dimensional framework. In I-III, the coordination of the Cu atom includes the N atom and three O atoms of the tetradentate chelate Nta^3- ligand and the X^- anion in the trans position with respect to N. The Cu-O bond lengths vary in the ranges 1.971-2.268 A in I, 1.958-2.289 A in II, and 2.040-2.110 A in III. The Cu-X bond lengths are 2.223, 2.364, and 2.354 A in I, II, and III, respectively. In I and II, the coordination polyhedron of the Cu atom is approximated by a distorted square pyramid with an O atom at the apical vertex, whereas in III, the polyhedron is described as a distorted trigonal bipyramid with the N and Br atoms at the axial sites. The structures are additionally stabilized by O(w)-H-O and O(w)-H-X hydrogen bonds

[en] 3-amino-4-hydroxy benzenesulfonamide and its hydrochloride have been isolated in the crystalline state. Their crystal and molecular structures are determined by X-ray diffraction. The equilibrium between neutral tautomeric forms of the 3-amino-4-hydroxy benzenesulfonamide molecule is studied within the approximation of density functional theory (B3LYP/aug-cc-pVDZ). The constants of acid-base equilibrium of 3-amino-4-hydroxy benzenesulfonamide are deter-mined using spectrophotometry.

[en] The crystal structure of 2,2’-(quinoxaline-2,3-diyl)dipyridinium dinitrate (H_2L)(NO_3)_2 is studied by X-ray diffraction (T = 150 K, R1 = 0.0467). The H_2L"2"+ cation is located on the twofold rotation axis and connected with two NO_3"− anions by strong N–H···O hydrogen bonds. Planar quinoxaline fragments of cations form stacks with the interplanar spacing of 3.308 Å. The structure of the diprotonated H_2L"2"+ cation is compared with those of the monoprotonated H_2L"2"+ cation and neutral L molecule.

[en] The structure of three complexes of bivalent metals (cobalt, nickel, and cadmium) with anions of benzoic (HL¹) and 2-(acetylamino)-5-nitrobenzoic (HL²) acids, namely, [Co₂¹ (H₂O)₂(μ-C₄H₄N₂)]_n (I), [NiL²(H₂O)₅]L² · 2H₂O (II), and [Cd(μ-L²)₂(H₂O)₂]_n · 2nH₂O (III), is determined. In chainlike structure I, cobalt atoms are connected by bridging pyrazine molecules; structure II contains isolated complexes. In structure III, centrosymmetric (CdOCO)₂ cycles and polymeric ribbons are formed due to the coordination of the carboxylate group of the L² ligand to two cadmium atoms.

[en] 5-Bromo-3-methoxysalicylidene-2-furfurylamine (HL⁵) and 3-nitrosalicylidene-2-furfurylamine (HL⁶) were synthesized and studied by X-ray diffraction. Both structures are stabilized by strong intramolecular N1–H1···O2 hydrogen bonds. Both molecules exist as zwitterions. The structure of the HL⁶ molecule has a contribution of the tautomeric quinoid form.