ELECTRON CORRELATION AND MOLECULAR SHAPE

1960 ◽  
Vol 38 (6) ◽  
pp. 818-826 ◽  
Author(s):  
R. J. Gillespie
Keyword(s):  
Electron Correlation ◽  
Polyatomic Molecule ◽  
Central Atom ◽  
Molecular Shape ◽  
Electron Pairs ◽  
Bond Lengths ◽  
Inverse Square Law ◽  
Lone Pairs ◽  
Electrostatic Repulsions

It is proposed that the arrangements of the electron pairs in the valency shell of a central atom of a polyatomic molecule can be predicted by considering the equilibrium arrangements of similar particles on the surface of a sphere with an appropriate law of force between the particles. The arrangements resulting from an inverse square law of force, corresponding to electrostatic repulsions, and a force which is proportional to 1/rn where n is large, corresponding to Pauli forces, are considered specifically. It is shown that the arrangements predicted agree with those found experimentally for molecules containing only non-transitional elements. The possible arrangements for seven, eight, and nine pairs of electrons in a valency shell are discussed in detail. A method is suggested for predicting the arrangements of electron pairs in valency shells containing lone pairs which can occupy alternative non-equivalent positions. The effect of the interactions of electron pairs on bond lengths in certain molecules is discussed. The extension of the same principles to molecules containing transitional elements is briefly outlined.

The duodecet rule: Part 3. Fluoro species of the third period elements

1992 ◽  
Vol 70 (6) ◽  
pp. 1696-1705 ◽  
Author(s):  
E. A. Robinson
Keyword(s):  
Bond Length ◽  
Molecular Species ◽  
Central Atom ◽  
Covalent Radius ◽  
Valence Shell ◽  
Single Bond ◽  
Electron Pairs ◽  
Bond Lengths ◽  
The Third

On the basis of the suggested new value of 54 pm for the single bond covalent radius of fluorine, the previously established duodecetrule for period 3 elements in molecular species with highly electronegative ligands is extended to fluorides. It is shown, for species such as SiF4, (F3Si)2O, F3SiNH2, F3PO, and PF5, that the observed bond lengths are consistent with significant partial double bonding involving all the ligands, including fluorine, and with a total of six electron pairs in the valence shell of the central atom. Empirical rules based on d/d1, the ratio of an observed bond length to the corresponding single bond length calculated from the sum of covalent radii, are developed as a simple approximate guide to the extent of partial double bonding in bonds to third period elements. It is also shown that bond lengths in species such as Al2F5, AlO45−, and Al(NH2)4− are consistent with a duodecet rule.

BOND LENGTHS AND BOND ANGLES IN OCTAHEDRAL, TRIGONAL- BIPYRAMIDAL, AND RELATED MOLECULES OF THE NON-TRANSITION ELEMENTS

1961 ◽  
Vol 39 (2) ◽  
pp. 318-323 ◽  
Author(s):  
R. J. Gillespie
Keyword(s):  
Central Atom ◽  
Lone Pair ◽  
Pauli Exclusion Principle ◽  
Exclusion Principle ◽  
Transition Elements ◽  
Electron Pairs ◽  
Bond Angles ◽  
Bond Lengths ◽  
Trigonal Bipyramidal ◽  
The Difference

The stereochemistry of molecules in which there are five or six pairs of electrons in the valency shell of a central atom is discussed in terms of the repulsions that exist between pairs of electrons in the valency shell as a consequence of the operation of the Pauli exclusion principle. An explanation is given for the difference in lengths of the axial and equatorial bonds in molecules such as PCl5 and ClF3 whose structures are based on the trigonal-bipyramidal arrangement of five valency-shell electron pairs. The fact that in molecules with a central atom with a valency shell of six electron pairs, one of which is a lone pair and which have the structure of a square pyramid, the central atom always lies below rather than in, or above, the base of the square pyramid, is also accounted for.

Extremal Electron Pairs — Application to Electron Correlation, Especially the R12 Method

1999 ◽  
pp. 21-42 ◽  
Author(s):  
Wim Klopper ◽  
Werner Kutzelnigg ◽  
Hendrik Müller ◽  
Jozef Noga ◽  
Stefan Vogtner
Keyword(s):  
Electron Correlation ◽  
Electron Pairs

Electron pairs, localized orbitals and electron correlation

2002 ◽  
Vol 100 (6) ◽  
pp. 757-781 ◽  
Author(s):  
LAIMUTIS BYTAUTAS ◽  
KLAUS RUEDENBERG
Keyword(s):  
Electron Correlation ◽  
Localized Orbitals ◽  
Electron 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.

Lone Pair Interactions in Zintl Phases and Intermetallic Compounds: Influence on Electronic Properties in Stannides and Plumbides

1998 ◽  
Vol 547 ◽  
Author(s):  
Thomas F. Fässler
Keyword(s):  
Intermetallic Compounds ◽  
Chemical Bond ◽  
Tight Binding ◽  
Lone Pair ◽  
Real Space ◽  
Localized States ◽  
Zintl Phases ◽  
Electron Pairs ◽  
Lone Pairs ◽  
Lone Pair Interactions

AbstractThe phases K6Sn23Bi2, K6Sn25, NaSn5, BaSn3, BaSn5, and K5Pb24 depict the structural transition from Zintl phases with localized chemical bonds to typical intermetallic compounds which may even have superconducting properties. The question of the nature of the chemical bond in these compounds is studied with the help of quantum mechanical calculations. Tight binding band structure calculations and real space representations using the Electron Localization Function (ELF) show that free electron pairs play a crucial role for the description of the chemical bond in polar intermetallic compounds. Interactions between lone pairs have a dominant influence on the electronic structures. The coincident appearance of quasi-molecular localized states in form of lone pairs and disperse delocalized bands at the Fermi level EF is discussed with respect to a ‘chemical view’ of the superconductivity observed for BaSn3, BaSn5, and K5Pb24.

Unusual 2 k   CDW state with enhanced charge ordering in P-(BEDT-TTF) AsF  and PF6

2002 ◽  
Vol 12 (9) ◽  
pp. 233-234
Author(s):  
Y. Nogami ◽  
T. Mori
Keyword(s):  
Organic Compounds ◽  
Coulomb Repulsion ◽  
Molecular Shape ◽  
Internal Degree ◽  
Charge Ordering ◽  
Two Dimensional ◽  
X Ray ◽  
Bond Lengths ◽  
Charge Modulation ◽  
Conformational Ordering

X-ray superstructure analyses of the $2k_{\rm F}$ CDW states for two-dimensional organic compounds β-(BEDT-TTF)2PF6 and AsF6 were presented Molecular ionicity of BEDT-TTF was evaluated with both intramolecular bond lengths and molecular shape. Strong bending of quasi-neutd BEDT-TTF molecules coupled with the enhanced amplitude of charge modulation was observed Conformational ordering of the terminal ethylenes of BEDT-TTF molecules anddmeriiation between quasi-ionic BEJYI-TTF molecules were also observed These characteristic indicates this CDW is not Peierls-Frohlich type but mupled with the internal degree of the molecular shape and possibly the intersite Coulomb repulsion.

A 6-31G* chemistry of isoelectronic tetrahedral XL4ε and YL4ε (X = Li to F; Y = Na to Cl; L = H, F, Cl) species. Part 2. Energies, bond lengths, and critical radii

1988 ◽  
Vol 66 (9) ◽  
pp. 2465-2475 ◽  
Author(s):  
S. C. Choi ◽  
Russell J. Boyd ◽  
Osvald Knop
Keyword(s):  
Central Atom ◽  
Energy Levels ◽  
Electronic Energy ◽  
Energy Requirements ◽  
Electronic Charge ◽  
Quadratic Polynomials ◽  
Bond Lengths ◽  
Total Electronic Energy ◽  
The Stability ◽  
Net Charges

The 6-31G* ab initio treatment of isoelectronic tetrahedral species now covers the complete XL4ε and YL4ε series (X = Li to F; Y = Na to Cl; L = H, F, Cl). The optimized equilibrium molecular parameters comprise the total electronic energy E, bond lengths, critical radii rc, MO energy levels, net charges, and electron densities at the bond critical points; only the first four are discussed in this part. The stability in terms of E, of the tetrahedral species relative to some competing systems, is examined. The energy requirements associated with the transfer of electronic charge from L to the central atom are reflected in the variation of the critical radii with the oxidation state m of X and Y, with important differences between the first- and the second-row elements. In an appendix it is shown that the E~HF limit energies of isoelectronic He-core (Li+ ff.), Ne-core (Na+ ff.), and Ar-core (K+ ff.) series of ions can be represented analytically by quadratic polynomials in m to an accuracy of ~0.0023% of the E~HF limit range or better, and that these approximations for the three series are qualitatively of the type E = −a(Z − b)2.

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