Active Lone Pair Of Electrons Research Articles

Sodium iodine(V) oxyfluoride, NaIO2F2

As an extension of a general structural study concerning fluorides and oxyfluorides of cations presenting a stereochemically active electronic lone pair, until now limited to tellurium(IV) phases, the previously unknown structure of NaIO(2)F(2) corresponds to a new structure type based on isolated IO(2)F(2)(-) polyhedra forming sheets separated by Na(+) layers. The sodium ion is octahedrally coordinated with 2/m site symmetry, while the I(V) atom has m2m symmetry with a stereochemically active lone electron pair. The O and F atoms (both with m symmetry) are bonded to the I(V) atoms in a fully ordered manner. A comparison with the structure of ferroelastic KIO(2)F(2) and with structures based on hexagonal close packing of anions, mainly rutile-type and FeTeO(3)F-type, reveals differences that are attributed to the smaller ionic radius of Na(+) and the ordering of the Na and I cations.

Crystal Structure of PbI2(ethylenediamine)2, catena-.MU.-Ethylenediamine-ethylenediaminediiodolead(II) at -150.DEG.C

The title complex is triclinic, P1, a = 7.585(3), b = 7.688(4), c = 12.737(6)A, α = 83.22(2), β = 73.731(19), γ = 63.38(2)°, V = 637.4(5)°3, and Z = 2 at -150°C; R is 0.0242. The structure shows a one-dimensional polymer extending along [111] with two crystallographically independent inversion centers lying at the middle of the C-C bond of each bridging ethylenediamine (en). The Pb atom is coordinated by two I atoms and four N atoms: the two I atoms occupy a cis-position, the two N atoms of a chelating en lie opposed to them, and the four atoms lie in a plane containing the Pb atom; the other two N atoms of the bridging en ligands lie at both axial positions. Since the I-Pb-I angle is 144.57(1)° wide, the Pb environment geometry might be described as being a distorted pentagonal bipyramid, providing a stereochemically active lone pair of electrons of the Pb atom may occupy one coordination site.

Tris(morpholine-4-dithiocarboxylato-κ2S,S′)antimony(III)

In the title compound, [Sb(C5H8NOS2)3], the SbIII ion adopts a distorted penta­gonal–pyramidal geometry because of its stereochemically active lone pair of electrons. In the crystal structure, the mol­ecules are associated into dimers by short inter­molecular Sb⋯S contacts [3.4111 (17) A].

Organotellurium Derivatives—Synthesis, Structure, Supramolecular Associations and SHG Efficiency

Non‐covalent interactions [Te‐‐‐X (X=Cl, Br, I, O, S)], secondary bonds, and C‐H‐‐‐X (X=O, I) hydrogen bonds induced supramolecular associations of organotelluriums have been synthesised and X‐ray characterised. The immediate coordination geometry around a central tellurium atom is a pseudotrigonal bipyramidal with a stereochemically active electron lone pair. Tetraorganotelluroxanes, charge transfer (CT) complexes and bis (ferrocenyl carboxylato) telluranes, possibly useful in material science, have been synthesised and X‐ray characterised. Select organotellurium derivatives have been tested for their second harmonic generation (SHG) efficiency. Cyclic voltammetric studies of ferrocenyl carboxylato derivatives show that they may be useful for two‐electron redox catalysis.

Synthesis and Structure of a Cadmium Selenite‐Sulfate Cd4(SeO3)2(SO4)2.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Crystal structure and chemical bonding in tin(II) acetate

Tin(II) acetate was prepared and its crystal structure was solved from X-ray powder diffraction data. Tin(II) acetate adopts a polymeric structure consisting of infinite Sn(CH 3COO) 2 chains running along the c-axis which are packed into groups of four. The acetate groups bridge the Sn atoms along the chains. The Sn atoms are asymmetrically surrounded by four oxygen atoms with two short Sn–O distances (2.170(6), 2.207(6) Å) and two longer ones (2.293(7), 2.372(8) Å). The coordination environment of the Sn atoms is completed up to a strongly distorted trigonal bipyramid SnO 4E by the sterically active lone electron pair E. The coordination environment of the Sn atoms is virtually identical for Sn(CH 3COO) 2 in the gaseous and solid phase: the two short Sn–O bonds and the lone electron pair are located in the equatorial plane of the trigonal bipyramid and the two longer Sn–O bonds are directed towards the apical vertexes. Localization of the lone electron pair on Sn(II) was confirmed by electron localization function (ELF) analysis. The polymeric nature of the tin(II) acetate crystal structure was confirmed by a MALDI-TOF experiment.

Crystal structure of the lead bromo-borate Pb2[B5O9]Br from precision single-crystal X-ray diffraction data and the problem of optical nonlinearity of hilgardites

The structural features responsible for the high nonlinear optical activity of crystals of the hilgardite-like anhydrous bromo-borate Pb2[B5O9]Br (space group Pnn2) are analyzed with the use of data obtained from two (precision and conventional) single-crystal X-ray diffraction experiments. The electron-density peaks associated with the stereochemically active lone electron pair are located in free space at two equally probable positions in the vicinity of the Pb(2) atom on the side of the two most distant atoms, Br(1) and Br(2). The stereochemical activity of two nonequivalent lead atoms in the crystal structure increases upon changing over from the Pb(1) atom to the Pb(2) atom. This is in agreement with the behavior of the lone electron pairs in the hilgardite-like hydrated borate Na0.5Pb2[B5O9](OH)1.5 · 0.5H2O and another nonlinear optical borate, namely, Pb2[B4O5(OH)4](OH)2 · H2O, which is related to the compound BiB3O6. The most pronounced nonlinear optical properties of the lead bromo-borate Pb2[B5O9]Br as compared to other orthorhombic hilgardites and lead borates are associated with the presence of highly polarized Pb-Br bonds. In this case, the electron density of the lone electron pair of the Pb(2) atom enhances the polarization effect.

Synthesis and Structure of a Cadmium Selenite-Sulfate Cd4(SeO3)2(SO4)2

Among them, however, no group-12 selenite-sulfate has been reported. Our interest in the selenite-basedstructures was concerned with the possible role of thestereochemically active lone pair of electrons as an invisiblestructure-directing agent to prepare unusual structures. Thestereochemically active lone pair of electrons in Se

Interaction of Different Metal Ions with Carboxylic Acid Group: A Quantitative Study

The binding strength of the carboxylic acid group (-COOH) with different divalent metal ions displays considerable variation in arachidic acid (AA) thin films. It is considered that in AA thin films the metal ions straddle the hydrophilic regions of the stacked bilayers of AA molecules via formation of carboxylates. In this study first the uptake of different divalent cations in films of AA is estimated by atomic absorption spectroscopy (AAS). Through the amount of cation uptake, it is found that the strength of binding of different cations varies as Ca2+>Co2+>Pb2+>Cd2+. Variation in the binding strength of different ions is also manifested in experiments where AA thin films are exposed to metal ion mixtures. The higher binding strength of AA with certain metal ions when exposed individually, as well as the preference over the other metal ions when exposed to mixtures, reveal some interesting deviation from the expected behavior based on considerations of ionic radii. For example, Pb2+ is always found to bind to AA much more strongly than Cd2+ even though the latter has smaller ionic radius, indicating that other factors also play an important role in governing the binding strength trends apart from the effects of ionic radii. Then, to get a more meaningful knowledge regarding the binding capability, first-principles calculations based on density functional theory have been applied to study the interaction of different cations with the simplest carboxylic acid, acetic acid, that can result in formation of metal diacetates. Their electronic and molecular structures, cohesive energies, and stiffness of the local potential energy well at the cation (M) site are determined and attempts are made to understand the diversity in geometry and the properties of binding of different metal ions with -COOH group. We find that the calculated M-O bond energies depend sensitively on the chemistry of M atom and follow the experimentally observed trends quite accurately. The trends in M-O bond energies and hence the total M-acetate binding energy trends can actually be related to their molecular structures that fall into different categories: Ca and Cd have tetrahedral coordination; Fe, Ni, and Co exhibit planar 4-fold coordination; and Pb is off-centered from the planar structure (forming pyramidal structure) due to its stereochemically active lone pair of electrons.

The solid solution Co3.6Mg1.4Cl2(TeO3)4

Single crystals of the cobalt magnesium dichloride tetra­kis[trioxotellurate(IV)] solid solution Co5−yMgy(TeO3)4Cl2 [y = 1.4] were obtained from solid–gas phase reactions in sealed evacuated silica tubes. The crystal symmetry is monoclinic and the compound is isostructural with Co5(TeO3)4X2 and Ni5(TeO3)4X2 (X = Cl, Br). The layered structure comprises distorted MO6 and MO5Cl octa­hedra (M = statistically occupied Co and Mg sites) and TeO3E tetra­hedra (E = stereochemically active electron lone pair of TeIV). Five face-sharing MO6 octa­hedra make up claw-like [M5O16Cl2] units which form layers by corner-sharing with four other such units and by corner- and edge-sharing with TeO3E tetra­hedra. The layers are held together only by weak van der Waals forces with a closest Te⋯Cl distance of 3.184 (2) A between two layers.

Hydrostatic compression of galenobismutite (PbBi2S4): elastic properties and high-pressure crystal chemistry

A single-crystal sample of galenobismutite was subjected to hydrostatic pressures in the range of 0.0001 and 9 GPa at room temperature using the diamond-anvil cell technique. A series of X-ray diffraction intensities were collected at ten distinct pressures using a CCD equipped 4-circle diffractometer. The crystal structure was refined to R1(|F0| > 4σ) values of approximately 0.05 at all pressures. By fitting a third-order Birch-Murnaghan equation of state to the unit-cell volumes V 0 = 700.6(2) A3, K 0 = 43.9(7) GPa and dK/dP = 6.9(3) could be determined for the lattice compression. Both types of cations in galenobismutite have stereochemically active lone electron pairs, which distort the cation polyhedra at room pressure. The cation eccentricities decrease at higher pressure but are still pronounced at 9 GPa. Galenobismutite is isotypic with CaFe2O4 (CF) but moves away from the idealised CF-type structure during compression. Instead of the two octahedral cation sites and one bi-capped trigonal-prismatic site, PbBi2S4 attains a new high-pressure structure characterised by one octahedral site and two mono-capped trigonal-prismatic sites. Analyses of the crystal structure at high pressure confirm the preference of Bi for the octahedral site and the smaller one of the two trigonal-prismatic sites.

Synthesis and crystal structure of two new Bi(III) complexes {(Me2NCS2)3Bi}2 and {[(CH2)5NCS2]2BiI}2

Six bismuth(III) complexes containing dithio-ligands formulated as (R2NCS2)3Bi [R2NCS2M = Me2NCS2Na, C4H8NCS2Na, Bz2NCS2Na] and [(R2NCS2)2BiI]2 [R2NCS2M = C5H10NCS2Na, n Bu2NCS2Na, OC4H8NCS2Na] have been obtained by reactions of bismuth(III) halides with dithiocarbamate ligands in 1 : 2 or 1 : 3 stoichiometry. All compounds were characterized by elemental and IR analyses. The crystal structures of complexes 1 and 4 have been determined by X-ray single crystal diffraction. The structure analyses reveal that BiIII in complex 1 adopts a distorted pentagonal–pyramidal coordination, due to its stereochemically active lone pair of electrons. A long Bi · S contact of 3.218 (3) Å leads to dimeric associations of molecules in the crystal structure. The structure of complex 4 is six-coordination with a distorted octahedral configuration. Intramolecular S · S weak interactions contribute to the stability and lead to a one-dimensional chain structure.

Thallium Halides — New Aspects of the Stereochemical Activity of Electron Lone Pairs of Heavier Main‐Group Elements

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Three new tellurite halides with unusual Te 4+ coordinations and iron honeycomb lattice variants

The crystal structure of three new iron and copper-iron tellurite halides are presented; ( I) Cu 3Fe 8Te 12O 32Cl 10 that crystallizes in the orthorhombic space group Pmmn, ( II) Fe 8Te 12O 32Cl 3Br 3 that crystallizes in the monoclinic space group P2 1/ c, and ( III) Fe 5(TeO 3) 6Cl 2 that crystallizes in the triclinic space group P-1. The crystal structures were solved from single crystal X-ray diffraction data. All three compounds have layered crystal structures where the Fe atoms form variants of the honeycomb lattice. Highly unusual Te 4+ coordination polyhedra are exemplified: [TeO 3+1 E], [TeO 3 XE], [TeO 3+1 XE], and [TeO 3 X 2 E] ( X=halide ion, E=the lone–pair valence electrons). The crystal structures contain large non-bonding volumes occupied by the stereochemically active lone–pair electrons on Te 4+.

Synthesis, spectral and structural characterisation of ditelluroxanes: μ-oxo-bis[nitrato-; 2,4,6-trinitrophenolato-dialkyl tellurium (IV)

The synthesis of ditelluroxanes: μ-oxo-bis[nitrato dimethyl tellurium (IV)] [(CH 3) 2TeNO 3] 2O ( 1), μ-oxo-bis[(2,4,6-trinitro)phenolato dimethyl tellurium (IV)] [(CH 3) 2TeOC 6H 2(NO 2) 3] 2O ( 2) and μ-oxo-bis[1-(2,4,6-trinitro)phenolato-1,1,2,3,4,5-hexahydrotellurophene] [C 4H 8TeOC 6H 2(NO 2) 3] 2O ( 3) was achieved. 1 was synthesised by the reaction of (CH 3) 2TeI 2 with fuming HNO 3 while 2 and 3 were synthesised by the reactions of R 2Te(OH) 2 [R 2 = (CH 3) 2, (C 4H 8)] ( in situ) with 2,4,6-trinitrophenol [ 2,4,6-(NO 2) 3C 6H 2OH] (picric acid). 1– 3 have been investigated through UV/Vis; FT-IR, ( 1H, 13C) NMR spectroscopy and single crystal X-ray diffraction studies. In 1– 3 the immediate coordination geometry about the central tellurium atom can be described as pseudo trigonal bipyramidal and the stereochemically active electron lone pair occupying equatorial position. The supramolecular self-organisations of these tetraorgano ditelluroxanes ( 1– 3) are explained through cooperative participation of Te⋯O secondary bonds, C–H⋯O hydrogen bonds and π-stacking of the organic substituents.

Modification of supramolecular assemblies based on C4H7(CH3)Te heterocycle and cooperative participation of intermolecular I···I, Te···I, Te···O secondary bonds; C(sp3)–H···O and C(sp2)–H···O hydrogen bonds

2-Methyl-1,1-dicarboxylato-1-telluracyclopentanes C4H7(CH3)Te(OCOR)2 (R=OCO, C6H5, 4-NO2C6H4, 3,5-(NO2)2C6H3, C6H5CH=CH, 4-OCH3C6H4) (2–7) were synthesised from the reactions of 2-methyl-1,1-diiodo-1-telluracyclopentane (1) and corresponding silver salts and characterised by (IR &1HNMR) spectroscopy. The structures of C4H7(CH3)TeI2 (1), C4H7(CH3)Te(OCOC6H5)2 (3) and C4H7(CH3)Te(4-NO2C6H4OCO)2 (4) were established by single crystal X-ray diffraction studies. The structures of 1, 3 & 4 (the immediate environment about tellurium is that of distorted trigonal bipyramidal geometry with a stereochemically active electron lone pair) are described in the context of their ability to generate intermolecular I···I, Te···I, Te···O secondary bonds; C(sp3)–H···O and C(sp2)–H···O hydrogen bonds leading to the formation of polymeric, tetrameric and trimeric supramolecular assemblies. The modification of supramolecular assembly present in the precursor 1 is demonstrated and the cooperative participation of C(sp2)–H···O & C(sp3)–H···O hydrogen bonds, probably, helpful in strengthening the supramolecular assembly is discussed.

Thallium Halides – New Aspects of the Stereochemical Activity of Electron Lone Pairs of Heavier Main‐Group Elements

AbstractDensity functional theory studies in the linear muffin tin approximation on thallium halides (TlX; X = F, Cl, Br, I) show that structural distortions due to a stereochemically active lone pair of electrons depend crucially on cation–anion interactions. Such distortions do not originate from a 6s–6p hybridisation on the heavy metal as the Tl 6s and 6p states are energetically too far apart to mix directly. In the case of TlF, the Tl 6s and the F 2p states are located in the same energy region, which leads to an efficient interaction that produces strongly antibonding Tl–F states directly below the Fermi level that would destabilize the solid. Minimisation of these unfavourable covalent antibonding interactions is the driving force for structural distortion. In the case of the heavier thallium halides, the growing energetic mismatch between Tl 6s states and X np states leads to weaker covalent interactions. Thus, the compounds become more ionic and high symmetry structures are adopted as covalent interactions play only a minor role. The low symmetry structure of TlI observed at low temperatures is stabilized by attractive metal–metal bonding. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Theoretical investigation of magnetoelectric behavior inBiFeO3

The magnetoelectric behavior of BiFeO$_3$ has been explored on the basis of accurate density functional calculations. The structural, electronic, magnetic, and ferroelectric properties of BiFeO$_3$ are predicted correctly without including strong correlation effect in the calculation. Moreover, the experimentally-observed elongation of cubic perovskite-like lattice along the [111] direction is correctly reproduced. At high pressure we predicted a pressure-induced structural transition and the total energy calculations at expanded lattice show two lower energy ferroelectric phases, closer in energy to the ground state phase. Band-structure calculations show that BiFeO$_3$ will be an insulator in A- and G-type antiferromagnetic phases and a metal in other magnetic configurations. Chemical bonding in BiFeO$_3$ has been analyzed using various tools and electron localization function analysis shows that stereochemically active lone-pair electrons at the Bi sites are responsible for displacements of the Bi atoms from the centro-symmetric to the noncentrosymmetric structure and hence the ferroelectricity. A large ferroelectric polarization (88.7 $\mu$C/cm$^{2}$) is predicted in accordance with recent experimental findings. The net polarization is found to mainly ($>$ 98%) originate from Bi atoms. Moreover the large scatter in experimentally reported polarization values is due to the large anisotropy in the spontaneous polarization.

A new nonlinear optical borate, Na0.5Pb2[B5O9](OH)1.5 · 0.5H2O, from the orthorhombic hilgardite family

A new polar representative of the hilgardite structural family, Na0.5Pb2[B5O9](OH)1.5 · 0.5H2O (space group Pnn2), is synthesized under hydrothermal conditions. The crystal structure of the compound synthesized is similar to the structure of the previously studied polar compound Na0.5Pb2[B5O9]Cl(OH)0.5 and is intermediate between the latter compound and the centrosymmetric hydrate Pb2[B5O9](OH) · 0.5H2O. The additional peak revealed in the electron density in the vicinity of the Pb(1) atom is attributed to the stereochemically active lone electron pair of this atom. The lone electron pair is oriented toward the two most distant oxygen atoms involved in the Pb(1) coordination environment, namely, O(7) and O(2), which are located in a boron-oxygen framework layer in the ac plane, not toward the (00z) channel occupied by water molecules. The nonequivalence in the stereochemical activity of two lead atoms [Pb(1) > Pb(2)] is similar to that observed in the nonlinear optical borate Pb2[B4O5(OH)4](OH)2 · H2O related to BiB3O6.

(Morpholine-1-dithiocarboxylato-κ2 S,S′)bis(piperidine-1-dithiocarboxylato-κ2 S,S′)bismuth(III)

In the title compound, [Bi(C5H8NOS2)(C6H10NS2)2], the BiIII atom adopts a distorted pentagonal–pyramidal coordination, due to its stereochemically active lone pair of electrons. A long Bi...S contact of 3.2727 (19) Å leads to dimeric associations of molecules in the crystal structure.