Relation between the bond lengths in an O-H…O bridge

The data in the literature on the bond lengths of O-H…O bridges formed in organic and inorganic crystals have been analyzed. The results of generalizations of these data on the basis of the generally accepted relation exp(?(r ₁ ? r ₀/b) + exp(?(r ₂ ? r ₀/b) = 1 are considered. The factors limiting its application are revealed and its limiting accuracy is estimated. A more universal expression relating the lengths of the same bonds is proposed: exp(?((r ₁ ? r ₀)/b) ^h ) + exp(?((r ₂ ? r ₀)/b) ^h ) = 1. On the basis of the generalization of all known neutron diffraction data on bridges with angles exceeding 165°, the coefficients in this relation are determined to be r ₀ = 0.950 ± 0.005, b = 0.33018 Å, and h = 5/3.     

Precision X-ray diffraction and Mössbauer studies and computer simulation of the structure and properties of malayaite CaSnOSiO<Subscript>4</Subscript>

The structure and some physical properties of malayaite CaSnOSiO₄ have been studied by the precision X-ray diffraction, Mössbauer spectroscopy, and computer simulation of the structure. The unit-cell parameters a = 7.152(2) Å, b = 8.888(2) Å, c = 6.667(2) Å, β = 113.37(2)°, V = 389.0(3) ų, and μr = 0.68 are refined on a synthetic impurity-free sample. The distribution of the deformation electron density is analyzed in the basic fragments of the crystal structure forming an anionic framework. The constructed potentials of pair and three-particle interaction reproduced quite well the elastic, dielectric, and energy characteristics and allowed us to predict their numerical values, which are in good agreement with the limited available experimental data.     

Synthesis and crystal structure of the iridium(I) carbene complex with a pair of hydrogen wing tips

The iridium(I) cyclooctadiene complex with two (3-tert-butylimidazol-2-ylidene) ligands [(H-Im^tBu)₂Ir(COD)]⁺PF₆^? (C₂₂H₃₂PF₆IrN₄) has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal atom, which is coordinated by two H-Im^tBu ligands and one cyclooctadiene group. The new iridium carbene complex has a pair of hydrogen wing tips. The Ir?C_carbene bond lengths are 2.066(5) and 2.052(5) Å, and the bond angle C?Ir?C between these bonds is 95.54(19)°. The dihedral angle between two imidazol-2-ylidene rings is 86.42°.     

Crystallographic analysis of the structure of livingstonite HgSb<Subscript>4</Subscript>S<Subscript>8</Subscript> from refined data

An X-ray diffraction study of mineral livingstonite (HgSb₄S₈) from Khaydarkan (Kyrgyzstan) has been performed on a Bruker Nonius X8Apex diffractometer with a 4K CCD detector (R = 0.031). The unit-cell parameters were found to be a = 30.1543(10) Å, b = 3.9953(2) Å, c = 21.4262(13) Å, β = 104.265(1)°, V = 2501.7(2) ų, Z = 8, d _calcd = 5.013 g/cm³, and sp. gr. A2/a. It was confirmed that livingstonite belongs to rod-layers structures. In one type of layer, two double Sb₂S₄ chains are bound by disulfide groups [S₂]^2? (S-S 2.078(2) Å); in the other type, these chains are bound via Hg²⁺ cations. A crystallographic analysis confirmed the existence of independent pseudotranslational ordering in the cation and anion matrices, which is characteristic of the lozenge-like structures of sulfides and sulfosalts.     

Crystal structures of two organic salts of 1,2,3,4-tetrahydro-1,10-phenanthroline

Two organic salts of 1,2,3,4-tetrahydro-1,10-phenanthroline (tphen), namely (oaH)(tphenH) (1) and (ssa)(tphenH)·H₂O (2) (oaH₂ is oxalic acid, ssaH is 5-sulfosalicylic acid), were synthesized and structurally characterized. Both compounds contain tphenH⁺ cations but illustrate different crystal structures. The tphenH⁺ cations show a cross-stacking packing model in 1 but display a herringbone packing model in 2.     

Unstrained bond lengths and corresponding cation radii in crystals with perovskite structure

A method for determining average lengths of unstrained bands A-X (l_0AX) and B-X (l_0BX) and the ratio of the rigidity constants of these bonds for ABX₃ compounds with perovskite structure is proposed. The values of l_0AX and l_0BX correspond to the minimum energies of cation-anion interaction of the crystal sublattices. Values of l_0AX and l_0BX are obtained for several groups of halide and oxide compounds: A⁺B²⁺F₃, Cs⁺B²⁺Cl₃, A⁺B⁵⁺O₃, A²⁺B⁴⁺O₃, and A³⁺B³⁺O₃. It is ascertained that, for most compounds studied, the values of l_0AX and l_0BX are equal or close to the interatomic distances in crystals of binary compounds. The values of l_0AX and l_0BX are compared with the sums of the radii of the corresponding cations (R _A , R _B ) and anions (\(^{VI} R_{O^{2 - } } ,^{VI} R_{F^ - } ,^{VI} R_{Cl^ - }\)). It is found that the differences \(l_{0AO^ - } ^{VI} R_{O^{2 - } } (L_{0AF^ - } ^{VI} R_{F^ - } )\) and \(l_{0BO^ - } ^{VI} R_{O^{2 - } } (l_{0BF^ - } ^{VI} R_{F^ - } )\), regarded as the radii of the A and B cations in unstrained bonds, are close to the Shannon radii for a coordination number of six. It is shown that the rigidity constant for A-X bonds is several times smaller than that for B-X bonds.     

Molecular structures of chalcone podands: A prognosis of photoinduced transformations in the crystals

A series of chalcone podands with the propenone group in the ortho position of the bridging aryl substituent with respect to the oxyethylene fragment is synthesized. The influence of the preorganization of the chalcone podand molecules in crystals on their ability to participate in topochemical reactions is investigated. From analyzing the X-ray structural data, the highest probability of the solid-state photochemical [2 + 2]cycloaddition is predicted for podands with phenyl substituents and the oxyethylene fragment containing two or three oxygen atoms. The X-ray structural data for the chalcone podand C₃₂H₂₆O₄ (3a) are as follows: a = 7.904(9) Å, b = 14.92(2) Å, c = 21.30(3) Å, β = 91.7(1)°, monoclinic system, space group P2₁/c, Z = 4, V = 2510(5) ų, ρ = 1.26 g/cm³, and R = 0.046; C₃₄H₃₀O₅ (3b): a = 15.738(9) Å, b = 11.889(2) Å, c = 15.0830(15) Å, β = 105.47(14)°, monoclinic system, space group C2/c, Z = 4, V = 2720.0(9) ų, ρ = 1.266 g/cm³, and R = 0.0418; C₃₂H₂₄N₂O₈ (4a): a = 17.9416(18) Å, b = 10.9703(8) Å, c = 41.699(2) Å, β = 105.970(11)°, monoclinic system, space group P2₁/c, Z = 4, V = 2781.4(5) ų, ρ = 1.348 g/cm³, and R = 0.0426; C₃₆H₃₂N₂O₁₀ (4c): a = 7.6286(5)Å, b = 17.9398(10) Å, c = 11.5890(3)Å, β = 95.287(4)°, monoclinic system, space group P2₁/n, Z = 2, V = 1579.27(14) ų, ρ = 1.372 g/cm³, and R = 0.0377; and C₂₈H₂₂O₆ (5a): a = 15.6032(10) Å, b = 8.1131(5) Å, c = 17.7334(11) Å, β = 91.381(5)°, monoclinic system, space group C2/c, Z = 4, V = 2244.2(2) ų, ρ = 1.345 g/cm³, and R = 0.0309.     

Synthesis and characterization of a lead(II) complex [Pb(phen)(H<Subscript>2</Subscript>O)(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>] (phen = 1,10-phenanthroline)

The monomeric lead(II) complex, [Pb(phen)(H₂O)(NO₃)₂] was prepared by a hydrothermal reaction of Pb(NO₃)₂, nitrilotriacetic acid, NaOH, 1,10-phenanthroline, and H₂O. The structure was determined by X-ray crystallography. It crystallizes in monoclinic P2(1)/n space group with the crystal cell parameters of a = 6.3568(6), b = 20.2345(19), c = 11.2722(9) Å, β = 98.337(4)^°, V = 1434.6(2) ų, and Z = 4. The crystal X-ray analysis shows that the lead atom is six-coordinated by two N atoms of phen ligand, three oxygen atoms of nitrate anions and one water molecule. Owing to the presence of a lone pair of electrons of lead atom, a significant gap occurs in the coordination geometry around Pb ion. A 3D architecture is formed through the strong hydrogen bonding and π–π stacking interactions.     

Synthesis and an X-ray diffraction study of Rb<Subscript>2</Subscript>[(UO<Subscript>2</Subscript>)<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>3</Subscript>]

The synthesis and X-ray diffraction study of compound Rb₂[(UO₂)₂(C₂O₄)₃], which crystallizes in the monoclinic crystal system, are performed. The unit cell parameters are as follows: a = 7.9996(6) Å, b = 8.8259(8) Å, c = 11.3220(7) Å, β = 105.394(2)°, and V = 770.7(1) ų; space group P2₁/n, Z = 2, and R ₁ = 0.0271. [(UO₂)₂(C₂O₄)₃]^2? layers belonging to the AK _0.5 ⁰² T ¹¹ crystal chemical group of uranyl complexes (A = UO ₂ ²⁺ , K ⁰² = C₂O ₄ ^2? , and T ¹¹ = C₂O ₄ ^2? ) are uranium-containing structural units of the crystals. The layers are connected with outer-sphere rubidium cations by electrostatic interactions.     

Stereoselective Synthesis and X-Ray Structure Determination of Labeled [1, 2, 3-<Superscript>13</Superscript>C<Subscript>3</Subscript>]-1-(Phenylsulfinyl)-3-Benzyloxyacetone

[1,2,3-¹³C₃]-1-(Phenylsulfinyl)-3-benzyloxyacetone, C₁₆H₁₆O₃S, (3) has been synthesized and its crystal structure has been determined by a single-crystal X-ray diffraction analysis. The X-ray diffraction study revealed that compound 3 crystallizes in the monoclinic crystal system in the acentric space group Pc, with cell constants at T = 100 K: a = 16.073(5), b = 5.5079(16), c = 7.949(2) Å, β = 100.221(4)^°, V = 692.6(3) ų, Z = 2, d _calc = 1.383 g/cm³. Compound 3 contains the chiral tetravalent three-coordinated sulfur atom, which has a distorted tetrahedral configuration with a lone electron pair occupying one of the tetrahedron vertices. In the crystal, the molecules are packed in stacks along the b axis; the stacks consist of the molecules of the same chirality. Furthermore, the stacks of the molecules of the opposite chirality alternate along the c axis. The molecules in neighboring stacks are arranged by head-to-tail orientations. There are no short intermolecular contacts in the crystal of 3.     

Investigation of structural transformations in pyridine nitrate at low temperatures and high pressures

The structural transformations in pyridine nitrate PyHNO₃ (C₅D₅NHNO₃) are investigated by neutron diffraction in the temperature range 16–300 K at normal pressure and in the high-pressure range 0–3.5 GPa at room temperature. A new high-pressure phase with a monoclinic structure (space group P2₁/c) is revealed in the PyHNO₃ compound at pressures P > P_tr ～ 1 GPa. The geometry of hydrogen bonds and the coordination of the PyH⁺ and NO ₃ ^? ions in the structure of the PyHNO₃ compound are studied as a function of the temperature and pressure.     

Structure of complexes of uranyl succinate with carbamide and dimethylurea

Three new succinate-containing complexes of uranyl with carbamide (Urea) and N,N'-dimethylurea (s-Dmur) are synthesized and studied by IR spectroscopy and X-ray diffraction. Structures of the same type, [UO₂(Urea)₄(H₂O)][(UO₂)₂(C₄H₄O₄)3] · 3H₂О and [UO₂(Urea)₄(H₂O)][(UO₂)₂(C₄H₄O₄)3] · 2Urea contain two sorts of uranium-containing complex groups, namely, mononuclear [UO₂(Urea)₄(H₂O)]²⁺ cations and two-dimensional [(UO₂)₂(C₄H₄O₄)₃]^2– anions described by crystal-chemical formulas AМ ₅ ¹ and A ₂ Q ₃ ⁰², respectively (A = UO₂ ²⁺, M ¹ = Urea or H₂O, Q ⁰² = C₄H₄O₄ ^2-), and differ only in the nature of noncoordinated molecules—water and carbamide. The main structural groups of the [(UO₂)₂(C₄H₄O₄)₂(s-Dmur)₃] crystals are [(UO₂)₂(C₄H₄O₄)₂(s-Dmur)₃] chains belonging to the А ₂ Q ₂ ⁰² M ₃ ¹ (A = UO₂ ²⁺, Q ⁰² = C₄H₄O₄ ^2-, M ¹ = s-Dmur) crystal-chemical group. Specific features of intermolecular interactions in the crystal structures are revealed using the Voronoi–Dirichlet method of molecular polyhedra.     

Structural study of 2,4,6-triisopropylbenzenesulfonyl chloride

The structure of 2,4,6-triisopropylbenzenesulfonyl chloride (TPSCl) (I) was studied by X-ray diffraction. Compound I is a highly selective condensing agent first suggested by Khorana for the formation of the C3′–C5′ interribonucleotide linkage in the oligo- and polyribonucleotide synthesis. I crystals are orthorhombic. At ?120°C, the unit-cell parameters are a = 14.184(4) Å, b = 11.344(5) Å, c = 19.883(6) Å, V = 3199(2) ų, d _calc = 1.257 g/cm³, Z = 8, sp. gr. Pbca. Molecule I adopts a strongly flattened boat conformation with the carbon atoms C-SO₂Cl (C ₁) and C-i-Pr (C4) of the benzene ring deviating from the bottom of the boat by 0.065(1) and 0.032(1) Å, respectively. Molecule I is sterically overcrowded, resulting in an increase in the bond lengths and bond-angle distortions in the fragment containing the SO₂Cl group and two ortho-i-Pr groups. Nonbonded contacts that are present in the molecule can be considered weak intramolecular hydrogen bonds (for example, the (CH₃)₂C-H?O=S bond). There is no rotation of the SO₂Cl, ortho-i-Pr, and CH₃ groups. The above-mentioned facts are, apparently, responsible for the specific selectivity of TPSCl. New readily available sterically hindered arenesulfonyl chlorides were designed.     

Crystal structure of zinc(II) hydrated trinuclear complex with monoprotonated ethylenediaminetetraacetate anion(3−), [Zn<Subscript>3</Subscript>(H<Emphasis Type="Italic">Edta</Emphasis>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>]

The crystal structure of the [Zn₃(HEdta)₂(H₂O)₆] complex (I) is determined by X-ray diffraction analysis. The crystals are orthorhombic, a = 14.780 Å, b = 29.699 Å, c = 7.032 Å, Z = 4, and space group Pna2₁. The structural units of crystals I are trinuclear linear molecules, in which the peripheral atoms Zn(1) and Zn(2) each coordinate two N atoms and three O atoms of the HEdta ^3? ligand and the O(w) atom of the H₂O molecule, whereas the central Zn(3) atom coordinates four O(w) atoms of the H₂O molecules and two terminal O atoms of the two HEdta ^3? ligands. The HEdta ^3? ligand fulfills a hexadentate chelating—bridging function. The bond lengths are as follows: Zn-O(HEdta), 2.006(4)–2.123(4) Å; Zn-N, 2.214(6) and 2.128(5) Å; and Zn-O(w), 2.006(6)–2.225(5) Å. In structure I, there is a specific contact formed by hydrogen bonds, owing to which the distance between the central atoms of individual molecules appears to be shorter than that in covalently bonded complexes.     

Synthesis and X-ray diffraction study of new uranyl malonate and oxalate complexes with carbamide

Two new malonate-containing uranyl complexes with carbamide of the formulas [UO₂(C₃H₂O₄)(Urea)₂] (I) and [UO₂(C₃H₂O₄)(Urea)₃] (II), where Urea is carbamide, and one uranyl oxalate complex of the formula [UO₂(C₂O₄)(Urea)₃] (III) were synthesized, and their crystals were studied by X-ray diffraction. The main structural units in crystals I are the electroneutral chains [UO₂(C₃H₂O₄)(Urea)₂]_∞ belonging to the crystal-chemical group AT¹¹M₂¹ (A = UO₂²⁺, T¹¹ = C₃H₂O₄^2-, M¹ = Urea) of uranyl complexes. Crystals II and III are composed of the molecular complexes [UO₂(L)(Urea)₃], where L = C₃H₂O₄^2- or C₂O₄^2-, belonging to the crystal-chemical group AB⁰¹M₃¹ (A = UO₂²⁺, B⁰¹ = C₃H₂O₄^2- or C₂O₄^2-, M¹ = Urea). The characteristic features of the packing of the uranium-containing complexes are discussed in terms of molecular Voronoi–Dirichlet polyhedra. The effect of the Urea: U ratio on the structure of uranium-containing structural units is considered.     

Specific features of the crystal structure and magnetic properties of KTaO<Subscript>3</Subscript> produced by electrolysis of melts

The magnetic susceptibility χ(T) at 4.2 K < T < 293 K; the dependence of the magnetic moment on the magnetic field strength, M(H), at 4.2, 77, and 293 K; and the electrical resistivity ρ(T) at 4.2 K < T < 293 K are studied for samples of perovskite-phase KTaO₃ obtained by both solid-phase synthesis (KTaO ₃ ^s ) and deposition on a cathode during electrolysis of melts (KTaO ₃ ^e ). Yellowish white KTaO ₃ ^s powders are diamagnetic and reveal dielectric properties. Dark polycrystalline KTaO ₃ ^e samples with metallic luster are characterized by the dependence ρ(T) typical of metals and additional paramagnetic contribution to the paramagnetic susceptibility as compared with KTaO ₃ ^e . Changes in the properties of KTaO₃ during electrocrystallization are attributed to partial reduction of tantalum. They are revealed in the structural features of KTaO ₃ ^e (excess of tantalum as compared to the stoichiometric composition of KTaO ₃ ^e , deficiency of the oxygen sublattice, and clearly pronounced anharmonicity of atomic vibrations). A change of the cation-anion-cation interactions, occurring owing to the overlapping of oxygen p orbitals with tantalum t_2g orbitals and the formation of impurity levels near the conduction band, leads to the generation of free carriers, which make a paramagnetic contribution to the magnetic susceptibility.     

Synthesis and crystal structure of Na<Subscript>3</Subscript>(H<Subscript>3</Subscript>O)[UO<Subscript>2</Subscript>(SeO<Subscript>3</Subscript>)<Subscript>2</Subscript>]<Subscript>2</Subscript>· H<Subscript>2</Subscript>O

Single crystals of the compound Na₃(H₃O)[UO₂(SeO₃)₂]₂ · H₂O (I) have been synthesized, and their structure has been investigated using X-ray diffraction. Compound I crystallizes in the triclinic system with the unit cell parameters a = 9.543(6)Å, b = 9.602(7)Å, c = 11.742(8)Å, α = 66.693(16)°, β = 84.10(2)°, γ = 63.686(14)°, space group P \(\bar 1\), Z = 2, and R = 0.0734. The uranium-containing structural units of the crystals are [UO₂(SeO₃)₂]^2? chains, which belong to the crystal-chemical group AB ² B ¹¹ (A = UO ₂ ²⁺ , B ² = SeO ₃ ^2? , B ¹¹ = SeO ₃ ^2? ) of the uranyl complexes. The structures of the compounds containing the [UO₂(SeO₃)₂]^2? anionic complexes are compared.     

Synthesis and structure of Cs[UO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)(OH)] · <Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O (<Emphasis Type="Italic">n</Emphasis> = 1.5 or 1)

The synthesis and single-crystal X-ray diffraction study of Cs[UO₂(SeO₄)(OH)] · 1.5H₂O (I) and Cs[UO₂(SeO₄)(OH)] · H₂O (II) are performed. Compound I crystallizes in the monoclinic crystal system, a = 7.2142(2) Å, b = 14.4942(4) Å, c = 8.9270(3) Å, β = 112.706(1)°, space group P2₁/m, Z = 4, and R = 0.0222. Compound II is monoclinic, a = 8.4549(2) Å, b = 11.5358(3) Å, c = 9.5565(2) Å, β = 113.273(1)°, space group P2₁/c, Z = 4, and R = 0.0219. The main structural units of crystals I and II are [UO₂(SeO₄)(OH)]^? layers which belong to the AT ³ M ² crystal chemical group of uranyl complexes (A = UO ₂ ²⁺ , T ³ = SeO₄ ^2?, and M ² = OH^?). In structure I, johannite-like layers are found. Structure II is a topological isomer of I. The two structures differ in the number of U(VI) atoms bound to the central atom by all bridging ligands.     

Structural chemistry of peroxo compounds of group VI transition metals: I. Peroxo complexes of chromium (a review)

The specific features revealed in the structure of the d ³ Cr(III), d ² Cr(IV), d ¹Cr(V), and d ⁰ 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_m A _p (n = 1, 2, 4; m = 0, 1; p = 0–4), the metal atoms can be in four oxidations states: +3 (d ³), +4 (d ⁴), +5 (d ¹), and +6 (d ⁰). This property distinguishes chromium peroxo compounds from molybdenum and tungsten dioxygen complexes, which, with one exception, are represented by the d ⁰ M(VI) compounds.     

X-ray diffraction study of Rb<Subscript>2</Subscript>[(UO<Subscript>2</Subscript>)<Subscript>2</Subscript>(CrO<Subscript>4</Subscript>)<Subscript>3</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>] · 4H<Subscript>2</Subscript>O

The compound Rb₂[(UO₂)₂(CrO₄)₃(H₂O)₂] · 4H₂O was studied by X-ray diffraction. The crystals are monoclinic, a = 10.695(2) Å, b = 14.684(3) Å, c = 14.125(3) Å, β = 108.396(4)°, sp. gr. P2₁/c, Z = 4, V = 2104.9(7) ų, and R = 0.0491. The main structural units are layers consisting of [(UO₂)₂(CrO₄)₃(H₂O)₂]^2? anions belonging to the crystal-chemical group A ₂ T ₂ ³ B ²M ₂ ¹ (A = UL ₂ ²⁺ , T ³ and B ² are CrO ₄ ^2? , and M ¹ is H₂O) of uranyl complexes. The uranium-containing layered groups are held together by electrostatic interactions with rubidium cations, as well as by hydrogen bonds with the participation of inner- and outer-sphere water molecules.