On the Structure of Tri- and Tetrahydroxolead(II) Complex Anions

2008 ◽  
Vol 73 (1) ◽  
pp. 59-72 ◽  
Author(s):  
Stanislava Šoralová ◽  
Martin Breza
Keyword(s):  
Hydrogen Bonds ◽  
Electronic Structures ◽  
Steric Effect ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Conformational Isomers ◽  
Conformational Isomer ◽  
Complex Anions

Optimal geometries and corresponding electronic structures of various [Pb(OH)3]- and [Pb(OH)4]2- conformational isomers are investigated by the B3LYP and MP2 treatments. Unlike highly symmetric [Pb(OH)3]- structure (C3 symmetry), the most stable [Pb(OH)4]2- conformational isomer has only C2 symmetry. Hydrogen bonds exhibit a lower influence on the stereochemistry of lead(II) hydroxocomplexes in comparison with the steric effect of the Pb(II) lone electron pair. The picture of the Pb(II) lone electron pair cannot explain the lowered symmetry of isolated [Pb(OH)4]2- complexes with four equivalent hydrogen bonds.

scholarly journals Crystal structures of the dioxane hemisolvates ofN-(7-bromomethyl-1,8-naphthyridin-2-yl)acetamide and bis[N-(7-dibromomethyl-1,8-naphthyridin-2-yl)acetamide]

2017 ◽  
Vol 73 (10) ◽  
pp. 1409-1413 ◽  
Author(s):  
Robert Rosin ◽  
Wilhelm Seichter ◽  
Monika Mazik
Keyword(s):  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Three Dimensional ◽  
Supramolecular Network ◽  
Halogen Bonds ◽  
Host Interactions ◽  
Compound Ii ◽  
Noncovalent Bonding

The syntheses and crystal structures ofN-(7-bromomethyl-1,8-naphthyridin-2-yl)acetamide dioxane hemisolvate, C11H10BrN3O·0.5C4H8O2, (I), and bis[N-(7-dibromomethyl-1,8-naphthyridin-2-yl)acetamide] dioxane hemisolvate, 2C11H9Br2N3O·0.5C4H8O2, (II), are described. The molecules adopt a conformation with the N—H hydrogen pointing towards the lone electron pair of the adjacent naphthyridine N atom. The crystals of (I) are stabilized by a three-dimensional supramolecular network comprising N—H...N, C—H...N and C—H...O hydrogen bonds, as well as C—Br...π halogen bonds. The crystals of compound (II) are stabilized by a three-dimensional supramolecular network comprising N—H...N, C—H...N and C—H...O hydrogen bonds, as well as C—H...π contacts and C—Br...π halogen bonds. The structure of the substituent attached in the 7-position of the naphthyridine skeleton has a fundamental influence on the pattern of intermolecular noncovalent bonding. While the Br atom of (I) participates in weak C—Br...Oguestand C—Br...π contacts, the Br atoms of compound (II) are involved in host–host interactionsviaC—Br...O=C, C—Br...N and C—Br...π bonding.

Structure at 200 and 298 K and X-ray investigations of the phase transition at 242 K of [NH2(CH3)2]3Sb2Cl9 (DMACA)

1996 ◽  
Vol 52 (2) ◽  
pp. 287-295 ◽  
Author(s):  
J. Zaleski ◽  
A. Pietraszko
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Hydrogen Bonds ◽  
Room Temperature ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Temperature Phase ◽  
Space Group ◽  
X Ray ◽  
Low Temperature Phase

[NH2(CH3)2]3Sb2Cl9 (dimethylammonium nonachlorodiantimonate, DMACA) has, at 200 K, a monoclinic Pc space group, with a = 9.470 (3), b = 9.034 (3), c = 14.080 (4) Å, β = 95.81 (3)°, V = 1198.4 (4) Å3, Z = 2 [R = 0.024, wR = 0.025 for 4613 independent reflections with F > 4σ(F)]. At 298 K DMACA has P21/c space group with a = 9.686 (3), b = 9.037 (3), c = 14.066 (4) Å, β = 95.57 (3)°, V = 1225.3 (5) Å3, Z = 2 [R = 0.034, wR = 0.035 for 2736 reflections with F > 4σ(F)]. The anionic sublattice of DMACA consists of polyanionic (Sb2Cl9 3−), layers. In the low-temperature phase there are three crystallographically non-equivalent dimethylammonium cations in the crystal structure. One of the cations is located inside the polyanionic layers, two others – one ordered and one disordered – between the polyanionic layers. In the room-temperature phase there are two non-equivalent cations – both disordered – in the crystal structure. Temperature dependencies of lattice parameters between 200 and 300 K were determined. The occurrence of a second-order phase transition at T = 242 K was confirmed. The dependence of lengths of Sb—Cl contacts on the presence and strength of N—H...CI hydrogen bonds was discussed. It was found that lengths of Sb—Cl bonds may differ from each other by as much as 0.3 Å, because of the presence of N—H...Cl hydrogen bonds. These differences were attributed to distortion of the lone-electron pair on antimony(Ill).

A new proposal for the electronic structure of carbon monoxide

2021 ◽  
Vol 34 (2) ◽  
pp. 193-200
Author(s):  
Stephan J. G. Gift
Keyword(s):  
Carbon Monoxide ◽  
Electronic Structure ◽  
Carbon Atom ◽  
Electronic Structures ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Cyanide Ion ◽  
Electron Transfer Mechanism ◽  
Pi Bonds ◽  
Sigma Bond

A new proposal for the electronic structure of carbon monoxide CO is presented. The approach involves the creation of an additional half-filled 2p orbital in the oxygen atom by the transfer of an electron from the filled 2p orbital to one of two half-filled hybridized <mml:math display="inline"> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi>s</mml:mi> <mml:msub> <mml:mi>p</mml:mi> <mml:mi>z</mml:mi> </mml:msub> </mml:mrow> </mml:math> orbitals in the carbon atom. The result is a triple bond comprising one sigma bond and two pi bonds between C and O strengthened by an ionic bond contribution. The proposed structure accounts for many unusual features of the molecule CO including the observed direction of the dipole moment, which is considered anomalous based on the concept of electronegativity of the constituent atoms as well as the increased bond dissociation energy compared with isoelectronic nitrogen <mml:math display="inline"> <mml:mrow> <mml:msub> <mml:mi>N</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> . It also provides a basis for the CO molecule being a stable ligand combining with transition metals using the lone electron pair in the filled <mml:math display="inline"> <mml:mrow> <mml:mn>2</mml:mn> <mml:mi>s</mml:mi> <mml:msub> <mml:mi>p</mml:mi> <mml:mi>z</mml:mi> </mml:msub> </mml:mrow> </mml:math> orbital of the carbon atom. The electron transfer mechanism is effectively applied to the isoelectronic compound boron monofluoride BF and predicts properties of the undetected isoelectronic molecule BeNe. Finally, the method proposes new electronic structures for the cyanide ion <mml:math display="inline"> <mml:mrow> <mml:mi>C</mml:mi> <mml:msup> <mml:mi>N</mml:mi> <mml:mo>−</mml:mo> </mml:msup> </mml:mrow> </mml:math> which resolves the long-standing puzzle of “charge reversal” on the molecule and the carbon monofluoride ion <mml:math display="inline"> <mml:mrow> <mml:mi>C</mml:mi> <mml:msup> <mml:mi>F</mml:mi> <mml:mo>+</mml:mo> </mml:msup> </mml:mrow> </mml:math> .

Two new thiophosphoramide structures:N,N′,N′′-tricyclohexylphosphorothioic triamide andO,O′-diethyl (2-phenylhydrazin-1-yl)thiophosphonate

2014 ◽  
Vol 70 (12) ◽  
pp. 1147-1152 ◽  
Author(s):  
Mehrdad Pourayoubi ◽  
Mozhgan Abrishami ◽  
Václav Eigner ◽  
Marek Nečas ◽  
Michal Dušek ◽  
...  
Keyword(s):  
Hydrogen Bonds ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Bond Angle ◽  
Mirror Plane ◽  
Acta Cryst ◽  
Bond Lengths ◽  
Planar Configuration ◽  
Structural Database ◽  
The Ideal

The compoundN,N′,N′′-tricyclohexylphosphorothioic triamide, C18H36N3PS or P(S)[NHC6H11]3, (I), crystallizes in the space groupPnmawith the molecule lying across a mirror plane; one N atom lies on the mirror plane, whereas the bond-angle sum at the other N atom has a deviation of some 8° from the ideal value of 360° for a planar configuration. The orientation of the atoms attached to this nonplanar N atom corresponds to anantiorientation of the corresponding lone electron pair (LEP) with respect to the P=S group. The P=S bond length of 1.9785 (6) Å is within the expected range for compounds with a P(S)[N]3skeleton; however, it is in the region of the longest bond lengths found for analogous structures. This may be due to the involvement of the P=S group in N—H...S=P hydrogen bonds. InO,O′-diethyl (2-phenylhydrazin-1-yl)thiophosphonate, C10H17N2O2PS or P(S)[OC2H5]2[NHNHC6H5], (II), the bond-angle sum at the N atom attached to the phenyl ring is 345.1°, whereas, for the N atom bonded to the P atom, a practically planar environment is observed, with a bond-angle sum of 359.1°. A Cambridge Structural Database [CSD; Allen (2002).Acta Cryst. B58, 380–388] analysis shows a shift of the maximum population of P=S bond lengths in compounds with a P(S)[O]2[N] skeleton to the shorter bond lengths relative to compounds with a P(S)[N]3skeleton. The influence of this difference on the collective tendencies of N...S distances in N—H...S hydrogen bonds for structures with P(S)[N]3and P(S)[O]2[N] segments were studied through a CSD analysis.

scholarly journals Localization and steric effect of the lone electron pair of the tellurium Te4+ cation and other cations of the p-block elements. A systematic study

2020 ◽  
Vol 53 (5) ◽  
pp. 1243-1251
Author(s):  
D. Hamani ◽  
O. Masson ◽  
P. Thomas
Keyword(s):  
Steric Effect ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Simple Method ◽  
Large Size ◽  
Oxide Crystal ◽  
Geometrical Concepts ◽  
Bottom Left ◽  
Anion Type ◽  
Small Charge

A simple method has been developed based on pure geometrical concepts to localize lone pairs (LPs) of cations of the p-block elements and model their steric effect. The method was applied to 1185 structures containing LP cations in 2439 non-equivalent positions. For oxide crystal structures, it is observed that, going from bottom left to top right in the periodic table, LPs move away from the cation core and decrease in size. For a given kind of cation M*, the LP radius increases linearly with the M*–LP distance, the smallest rate being observed for Tl+ and the largest for Cl5+. The influence of the anion type was also studied in the case of the Te4+ cation. Overall, the same trends were observed. The smallest Te–LP distances and LP radii are found for anions of large size and small charge.

scholarly journals Metal-Rich Metallaboranes: Synthesis, Structures and Bonding of Bi- and Trimetallic Open-Faced Cobaltaboranes

Inorganics ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 28
Author(s):  
Kriti Pathak ◽  
Chandan Nandi ◽  
Jean-François Halet ◽  
Sundargopal Ghosh
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Room Temperature ◽  
Electron Pair ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Cluster 2 ◽  
Cobalt Center

Synthesis, isolation, and structural characterization of unique metal rich diamagnetic cobaltaborane clusters are reported. They were obtained from reactions of monoborane as well as modified borohydride reagents with cobalt sources. For example, the reaction of [Cp*CoCl]2 with [LiBH4·THF] and subsequent photolysis with excess [BH3·THF] (THF = tetrahydrofuran) at room temperature afforded the 11-vertex tricobaltaborane nido-[(Cp*Co)3B8H10] (1, Cp* = η5-C5Me5). The reaction of Li[BH2S3] with the dicobaltaoctaborane(12) [(Cp*Co)2B6H10] yielded the 10-vertex nido-2,4-[(Cp*Co)2B8H12] cluster (2), extending the library of dicobaltadecaborane(14) analogues. Although cluster 1 adopts a classical 11-vertex-nido-geometry with one cobalt center and four boron atoms forming the open pentagonal face, it disobeys the Polyhedral Skeletal Electron Pair Theory (PSEPT). Compound 2 adopts a perfectly symmetrical 10-vertex-nido framework with a plane of symmetry bisecting the basal boron plane resulting in two {CoB3} units bridged at the base by two boron atoms and possesses the expected electron count. Both compounds were characterized in solution by multinuclear NMR and IR spectroscopies and by mass spectrometry. Single-crystal X-ray diffraction analyses confirmed the structures of the compounds. Additionally, density functional theory (DFT) calculations were performed in order to study and interpret the nature of bonding and electronic structures of these complexes.

Synthesis, Electronic Structure and Anti-Cancer Activity of the Phenyl Substituted Pyrazolo[1,5-a][1,3,5]triazines

2021 ◽  
Vol 25 ◽  
Author(s):  
Evgenia S. Veligina ◽  
Nataliya V. Obernikhina ◽  
Stepan G. Pilyo ◽  
Oleksiy D. Kachkovsky ◽  
Volodymyr S. Brovarets
Keyword(s):  
Electronic Transition ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Anti Cancer ◽  
Protein Molecules ◽  
Biological Affinity ◽  
Cancer Types ◽  
Derivatives Of ◽  
Cancer Activity

: Background: Synthesis of a series of 2-(dichloromethyl)pyrazolo[1,5- a][1,3,5]triazines was carried out and evaluated in vitro for their anticancer activity against a panel of 60 cell lines derived from nine cancer types. The joint quantum-chemical and experimental study of the influence of the extended πconjugated phenyl substituents on the electron structure of the pyrazolo[1,5-a][1,3,5]triazines as Pharmacophores were performed. It is shown that the decrease in the barriers to the rotation of phenyl substituents in compounds 1-7 possibly leads to an increase in the anti-cancer activity, which is in agreement with the change in the parameter biological affinity ϕ0. Analysis of the S0 → S1 electronic transitions (π→π*) of the pyrazolo[1,5-a][1,3,5]triazines shows that an increase in their intensity correlates with anti-cancer activity. Thus, the introduction of phenyl substituents increases the likelihood of investigated pyrazolo[1,5-a][1,3,5]triazines interacting with protein molecules (Biomolecule) by the π stacking mechanism. In both methyl and phenyl derivatives of pyrazolo[1,5-a][1,3,5]triazines, the second electronic transition includes the n-MO (the level of the lone electron pair in two-coordinated nitrogen atoms). The highest intensity of the η→π* electronic transition is observed in pyrazolo[1,5-a][1,3,5]triazine with pyridine residue, which does not exhibit anti-cancer activity, but exhibits antiviral activity [13]. It can be assumed that the possibility of the formation of [Pharmacophore-Biomolecule] complex by hydrogen bonding ([H-B]) mechanism with protein molecules increases.

scholarly journals Synthesis, Crystal Structure and Vibrational Properties of bis (N-benzylmethylammonium) Pentachlorobismuthate (III)

2012 ◽  
Vol 8 (2) ◽  
pp. 1566-1580 ◽  
Author(s):  
Hiba Khili ◽  
Najla Chaari ◽  
Mohamed Fliyou ◽  
Slaheddine Chaabouni
Keyword(s):  
Lone Electron Pair ◽  
Electron Pair ◽  
Crystal Packing ◽  
Three Dimensional ◽  
Average Density ◽  
Infrared And Raman Spectra ◽  
Organic Layers ◽  
Dimensional Network ◽  
Anionic Layer ◽  
Inorganic Layers

The [C8H12N]2 BiCl5 compound crystallised in the triclinic system with space group  P-1  with a = 9,833(4),                     b = 10,044(7), c = 12,225(7) Å, a= 78.82(4), β = 75,42(4), g= 76.89°(5)  and Z = 2. The average density value, ρx = 1.518 g.cm-3  is in agreement with the calculated one, ρx = 1.494 g.cm-3. The atomic arrangement can be described as an alternation of organic and inorganic layers. The anionic layer is built up of octahedral [Bi2Cl10]-4. The organic layers are arranged in sandwich between the anionic ones. The crystal packing is governed by means of the ionic N–H---Cl hydrogen bonds, forming a three dimensional network. The nature of the distortion of the inorganic polyhedra has been studied and can be attributed to the stereo activity of the Bi(III) lone electron pair. The infrared and Raman spectra was recorded in the 4000–400 cm-1 frequency region.

Darstellung und Kristallstruktur von Tl4TiS4, TI4SnS4 und Tl4TiSe4 / Preparation and Crystal Structure of Tl4TiS4, TI4SnS4 and Tl4TiSe4

1984 ◽  
Vol 39 (6) ◽  
pp. 705-712 ◽  
Author(s):  
Kurt O. Klepp ◽  
Günther Eulenberger
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Crystal Structures ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Monoclinic System ◽  
The Mean ◽  
Similar Description ◽  
Oriented Parallel ◽  
Stereochemical Activity

AbstractThe isostructural compounds Tl4TiS4, Tl4SnS4 and Tl4TiSe4 crystallize in the monoclinic system, space group P21/c with a = 8.328, b = 8.191, c = 15.248 Å, β = 104.53°; a = 8.395, b = 8.280, c = 15.398 A, ft = 103.69°, and a = 8.517, b = 8.389, c = 15.672 Å, β = 103.50°, respectively. There are four formula units in the unit cell. The crystal structures were determined and refined from single crystal diffractometer data. They are characterized by isolated tetrahedral thioanions which are connected with each other by Tl+ ions. The mean bond lengths are Ti-S = 2.26 Å, Sn-S = 2.40 Å and Ti -Se = 2.38 Å. The Tl atoms are surrounded by six and seven chalcogen atoms, respectively, in an irregular and polar arrangement, thus indicating stereochemical activity of the lone electron pair of the Tl+ ions. Tl-S distances vary from 2.93 to 3.98 Å, Tl-Se distances from 3.03 to 3.96 Å. The Tl atoms have nearest Tl neighbours at distances ranging from 3.46 to 3.65 Å. The crystal structure can be described as built from pseudotetragonal slabs oriented parallel to (001) which contain the cations and the tetrahedral anions. It is shown that a similar description is valid also for the crystal structures of Tl4GeS4 [1] and Na4SnS4 [2, 3].

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