A comment on the structure of xenon hexafluoride

1978 ◽  
Vol 31 (9) ◽  
pp. 1917 ◽  
Author(s):  
DL Kepert
Keyword(s):  
Electron Pair ◽  
Lone Pair ◽  
Xenon Atom ◽  
Electron Pairs ◽  
Repulsion Energy ◽  
A Value ◽  
Bonding Electron

Calculations based on the minimization of the repulsion energy between electron pairs show that the structure of xenon hexafluoride is predicted if the non-bonding electron pair is situated close to the xenon atom. If a value of n = 6 is assumed in the repulsion law, the distance between the xenon atom and the effective centre of repulsion of the lone pair is approximately 10% of the distance between the xenon atom and the effective centres of repulsion of the bonding pairs.

The role of non-bonding electron pairs in the asymmetric coordination environments of 1,1-dithiolate complexes

1976 ◽  
Vol 29 (11) ◽  
pp. 2541 ◽  
Author(s):  
BF Hoskins ◽  
CD Pannan
Keyword(s):  
Electron Pair ◽  
Central Atom ◽  
Main Group ◽  
Valence Shell ◽  
Electron Pairs ◽  
Shell Electron ◽  
Dithiolate Complexes ◽  
Asymmetric Coordination ◽  
Bonding Electron

Various forms of asymmetry in the lengths of the bond between the central atom and sulphur, found in differing coordination environments of 1,1-dithiolate compounds involving main group atoms, have been successfully rationalized by considering both the valence shell electron pair repulsion theory and the effect of the restricted ligand bite distance.

Oxotellurate(IV) der Lanthanide: II. Die isotype Reihe M2Te5O13 (M = Dy – Lu) / Oxotellurates(IV) of Lanthanides: II. The Isotypic Series M2Te5O13 (M = Dy – Lu)

2005 ◽  
Vol 60 (7) ◽  
pp. 720-726 ◽  
Author(s):  
Steffen F. Meier ◽  
Thomas Schleid
Keyword(s):  
Electron Pair ◽  
Three Dimensional ◽  
Lone Pair ◽  
Formula Unit ◽  
Partial Structure ◽  
Tellurium Oxide ◽  
Stereochemical Activity ◽  
Formula Type ◽  
Trigonal Prismatic ◽  
Bonding Electron

For the shortly discovered formula type M2Te5O13 (triclinic, P1̄), the establishment of an isostructural series in the last third of the lanthanide family (M = Dy - Lu) was possible. The excessive formula unit TeO2 additional to the well-known composition M2Te4O11 (monoclinic, C2/c) leads to the slicing of the [M2O10]14− layers which are typical for the tellurium-oxide poorer compounds. By coupling together the bicapped trigonal prismatic (M1, CN = 8) and the pentagonal bipyramidal (M2, CN = 7) lanthanide-oxygen polyhedra via edges, [M4O20]28− bands are formed stretching along the a axis and piling up to a primitive rod-packing. The linkage of these bands occurs parallel to the (010) plane via Te3 as well as via Te4 parallel to (100). Besides the usual 3+1 coordination, two of the five crystallographically independent tellurium sites are coordinated regularly fourfold (d(Te−O) ≈ 186−213 pm) and even 3+2-fold by oxygen atoms. The tellurium-oxygen polyhedra form corrugated layers running parallel to (101) which follow so close to each other that the tellurium-oxygen partial structure appears to be almost three-dimensional at a passing glance. As in M2Te4O11-type representatives, the non-bonding electron pair (lone pair) of each Te4+ cation shows stereochemical activity which always appears to flock together in large tellurium neighboured positions.

Die Lanthanoid(III)-Oxid-Oxoselenate(IV) Ln2O[SeO3]2 (Ln=Sm–Tm)

2016 ◽  
Vol 71 (12) ◽  
pp. 1279-1285 ◽  
Author(s):  
Joseph Wontcheu ◽  
Sabine Zitzer ◽  
Thomas Schleid
Keyword(s):  
Crystal Structure ◽  
Three Dimensional ◽  
Lone Pair ◽  
Selenium Dioxide ◽  
Channel Structure ◽  
Solid State Reactions ◽  
Molar Ratio ◽  
Electron Pairs ◽  
Dimensional Network ◽  
Bonding Electron

AbstractSingle crystals of compounds with the composition Ln2O[SeO3]2 (Ln=Sm–Tm) were synthesized by solid-state reactions of the lanthanoid sesquioxides (Ln2O3) with the corresponding tribromides (LnBr3) and selenium dioxide (SeO2) in a molar ratio of 2:1:2 in evacuated torch-sealed silica ampoules. For the terbium case, Tb4O7 and SeO2 have been reacted with elemental Tb in a molar ratio of 3:14:2. These lanthanoid(III) oxide oxoselenates(IV) all crystallize tetragonally with the space group P42/ncm and decreasing lattice parameters from the lighter to the heavier Ln3+ cations (from a=1077.03(8) pm and c=526.38(4) pm for Ln=Sm to a=1049.60(8) pm and c=516.04(4) pm for Ln=Tm) according to the lanthanide contraction. They show a three-dimensional network of condensed [LnO8]13− polyhedra with a channel structure, where all ψ1-tetrahedral [SeO3]2− units are coordinating with their O2− anions to square antiprisms [LnO8]13− and pointing with their non-bonding electron pairs into the empty channels, which propagate along [001]. As another characteristic feature of the crystal structure, [OLn4]10+ tetrahedra containing the non-selenium-bonded O2− anions are trans-edge-connected to form ${}_\infty ^{\rm{1}}{\rm{\{ [O}}Ln_{4/2}^{\rm{e}}{{\rm{]}}^{{\rm{4}} + }}{\rm{\} }}$ chains, which run parallel to the lone-pair channels in [001] direction and build up a tetragonal rod-packing.

The Contribution To Bond Valences By Lone Electron Pairs

2004 ◽  
Vol 848 ◽  
Author(s):  
Xiqu Wang ◽  
Friedrich Liebau
Keyword(s):  
Coordination Sphere ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Lone Pair ◽  
Bond Valence ◽  
Alkali Cations ◽  
Continuous Increase ◽  
Electron Pairs ◽  
Effective Valence

ABSTRACTBond valence sums (BVS) calculated for lone-pair cations are found increasingly higher than their formal valences as the retraction of the lone electron pair (LEP) from the nucleus is more pronounced. The increase in BVS is interpreted as a continuous increase of an effective valence of an atom that is a measure of its actual ability to bind other atoms without changing its formal valence. How the LEP of a lone-pair cation affects the effective valence of other atoms in a structure is studied by bond valence calculations for specific structures. For structures rich in alkali cations, it is found that the high effective valence of the lone-pair cations tends to be balanced by low effective valence of alkali cations. The LEP transfers bonding power or effective valence from the alkali cations to the lone-pair cations by joining the coordination sphere of the alkali cations.

Structure and bonding in cyclic phosphoramidates as determined by carbon-13 magnetic resonance

1979 ◽  
Vol 57 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Gerald W. Buchanan ◽  
Frederick G. Morin
Keyword(s):  
Magnetic Resonance ◽  
Nitrogen Atom ◽  
Electron Pair ◽  
Chemical Shifts ◽  
Lone Pair ◽  
Ring Conformation ◽  
Delocalized Electron ◽  
Nitrogen Lone Pair ◽  
Structure And Bonding

13C chemical shifts and 13C–31P couplings are reported for 11 cyclic phosphoramidates of ring sizes from four to nine. Vicinal couplings are compared with those of carbocyclic analogs and provide insight regarding the degree of nitrogen lone pair derealization into the N—P bond. For six-membered and larger rings, there appears to be nearly complete lone pair delocalization, i.e., a trigonal planar nitrogen atom. In azetidine derivatives the nitrogen lone pair remains localized, giving rise to a highly puckered ring conformation. Pyrrolidine derivatives are viewed as having a nitrogen with a partially delocalized electron pair.

Studies on bond and atomic valences. I. correlation between bond valence and bond angles in SbIII chalcogen compounds: the influence of lone-electron pairs

1996 ◽  
Vol 52 (1) ◽  
pp. 7-15 ◽  
Author(s):  
X. Wang ◽  
F. Liebau
Keyword(s):  
Statistical Analysis ◽  
Valence State ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Bond Valence ◽  
Continuous Change ◽  
Oxidation Number ◽  
Electron Pairs ◽  
Atomic Valence ◽  
Bond Valence Parameter

In the present bond-valence concept the bond-valence parameter ro is treated as constant for a given pair of atoms, and it is assumed that the bond valence sij is a function of the corresponding bond length Dij , and that the atomic valence is an integer equal to the formal oxidation number for Vi derived from stoichiometry. However, from a statistical analysis of 76 [SbIIIS n ] and 14 [SbIIISe n ] polyhedra in experimentally determined structures, it is shown that for SbIII—X bonds (X = S, Se), ro is correlated with {\bar \alpha} i , the average of the X—Sb—X angles between the three shortest Sb—X bonds. This is interpreted as a consequence of a progressive retraction of the 5s lone-electron pair from the SbIII nucleus, which can be considered as continuous change of the actual atomic valence act Vi of Sb from +3 towards +5. A procedure is derived to calculate an effective atomic valence eff Vi of SbIII from the geometry, {\bar \alpha} i and Dij , of the [SbIII Xn ] polyhedra, which approximates act Vi and is a better description of the actual valence state of SbIII than the formal valence for Vi . Calculated eff V SbIII are found to vary between +2.88 and +3.80 v.u. for [SbIIIS n ] and between +2.98 and +3.88 v.u. for [SbIIISe n ] polyhedra. It is suggested that a corresponding modification of the present bond-valence concept is also required for other cations with lone-electron pairs.

scholarly journals Lone-pair effect on carrier capture in Cu2ZnSnS4solar cells

2019 ◽  
Vol 7 (6) ◽  
pp. 2686-2693 ◽  
Author(s):  
Sunghyun Kim ◽  
Ji-Sang Park ◽  
Samantha N. Hood ◽  
Aron Walsh
Keyword(s):  
Solar Cells ◽  
Fast Electron ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Lone Pair ◽  
Electron Hole ◽  
Carrier Capture ◽  
Hole Recombination

Fast electron–hole recombination in kesterite solar cells is linked to the chemistry of the Sn lone electron pair.

Structure of russellite (Bi2WO6): origin of ferroelectricity and the effect of the stereoactive lone electron pair on the structure

2018 ◽  
Vol 74 (3) ◽  
pp. 295-303 ◽  
Author(s):  
Hiroki Okudera ◽  
Yuka Sakai ◽  
Kentaro Yamagata ◽  
Hiroaki Takeda
Keyword(s):  
Low Temperature ◽  
Lone Electron Pair ◽  
Electron Pair ◽  
Lone Pair ◽  
Orthorhombic Phase ◽  
Electrostatic Charge ◽  
X Ray Diffraction ◽  
Coordination Environment ◽  
X Ray ◽  
Powder Neutron Diffraction

The structure of the low-temperature polar (orthorhombic) phase of russellite (Bi2WO6) was examined on artificial specimens with precise single-crystal X-ray diffraction experiments. The final atomic arrangement thus obtained was identical to that reported by Knight [Miner. Mag. (1992), 56, 399–409] with powder neutron diffraction. The residual density attributable to a stereochemically-active lone pair of electrons of bismuth was prominent at approximately the centre of a larger cap of BiO8 square antiprisms, that is on the line from the Bi sites to an adjacent WO4 2− slab along the b-axis direction. Quite uneven Bi—O distances and the formation of a vacant coordination hemisphere (within 3 Å) should, therefore, be ascribed to the strong demand of bismuth to form shorter Bi—O bonds to use up its electrostatic charge within its coordination environment. The shift of bismuth along −c propagates via the correlated shift of the W site and these cooperative shifts cause ferroelectricity in the compound. This propagation was easily effected by the intrusion of molecules such as acetone into the structure.

Die monoklinen Seltenerdmetall(III)-Chlorid-Oxidoarsenate(III) mit der Zusammensetzung SE5Cl3[AsO3]4 (SE=La–Nd, Sm)

2019 ◽  
Vol 74 (6) ◽  
pp. 497-506 ◽  
Author(s):  
Felix C. Goerigk ◽  
Svetlana Schander ◽  
Makram Ben Hamida ◽  
Dong-Hee Kang ◽  
Florian Ledderboge ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Lone Pair ◽  
Earth Metal ◽  
Metal Compounds ◽  
Coordination Polyhedra ◽  
Electron Pairs ◽  
Space Groups ◽  
Coordination Numbers ◽  
Oxygen Atoms

AbstractThe rare earth metal(III) chloride oxidoarsenates(III) with the composition RE5Cl3[AsO3]4 (RE = La–Nd, Sm) could be synthesized via solid-state methods through the reaction of arsenic sesquioxide (As2O3) with the corresponding rare earth metal compounds (La2O3, CeO2 + metallic Ce, Pr6O11, Nd2O3 or metallic Sm) using several chloride-containing fluxing agents in evacuated silica glass ampoules. The compounds build up non-isotypic crystal structures in the monoclinic space groups C2/c for RE = La–Pr, and P2/c for RE = Nd and Sm. All rare earth metal(III) cations exhibit coordination numbers of eight. While (RE1)3+ and (RE2)3+ are only surrounded by oxygen atoms in the form of distorted square antiprisms or prisms, (RE3)3+ is coordinated square antiprismatically by four oxygen atoms and four chloride anions. Although the coordination polyhedra in both structures differ only marginally, their connection patterns show more pronounced differences. This regards especially the (RE)3+ cations and results from different site symmetries of the (Cl1)− anions. All As3+ lone-pair cations are coordinated by three oxygen atoms to form ψ1-tetrahedral [AsO3]3− complex anions with their non-binding (lone) electron pairs pointing into empty channels along [010].

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