Pauling Electronegativities Research Articles

121Sb-Mößbauerspektroskopische Untersuchungen von Graphit-Intercalationsverbindungen des Typs Cn · SbCl5 · MCl3 (M = Al, Fe, Sb, As)

Using 121Sb Moessbauer spectroscopy information concerning both ionicity and valence stale of the intercalate in ternary graphite intercalation compounds (GIC) can be obtained. It has been proved that the major portion of antimony in the SbCl5/MCl3-GIC has the valence state of Sb(V) whereas oxidation of the graphite is to be expected only to an insignificant extent. Two different antimony phases of a neutral and a negatively charged species were shown to exist by evaluation of the spectra in the Sb(V) region. In comparison with the binary SbCl5-GIC the changes of the isomer shift may be a consequence of intermolecidar interactions with the trichlorides. These changes are in accordance with Pauling's electronegativities. Assuming the existence of polymeric anions consisting of the species SbCl5, SbCl6 − and MCl3 in the interlaminary spacings an interpretation of the spectra is given. For the ternary GIC the following structure is suggested Cn +(m SbCl5 · p MCl3 · q SbCl6)−, at which M = Al, Fe, Sb and As is, respectively. The trichlorides act as links between the Sb species.

Thermodynamic Prediction of Sulfide Capacities in Na2O-SiO2 Melts

Sulfide capacities of Na2O-SiO2 melts at 1473 and 1623 K were calculated a priori from a model using free energies of formation of Na2S and Na2O and the activities of Na2O in the binary Na2O-SiO2 melts. Our calculations are in excellent agreement with available experimental data and appear to be more more accurate than currently used empirical predictions of sulfide capacities, based on correlations with optical basicities using Pauling electronegativities.

Relation between heats of formation of alkali and pseudo-alkali halides and electronegativities of halogen ions

The heats of formation of alkali halides (CsX, RbX, KX, NaX, LiX) and pseudo-alkali halides (NH 4X, TlX, CuX, AgX, AuX), −Δ H 0 298, are empirically expressed by the electronegativities (χ a) of the halogen ion: ▪ where a and b are empirical constants; e, r C and r A represent the charge on the electron, cation radius, and anion radius, respectively. The value of ± e 2/ r (C and/or a) corresponds to the electrostatic energy between the effective nuclear charge of the M + and/or X − ion and an electron at a distance from its nucleus equal to its ionic radius r C and/or r A. The empirical constants a and b correlate with the electronegativity of the M + ion in two different trends; one is the alkali ion series and the other is the pseudo-alkali ion series. This means that Pauling's electronegativities of alkali and pseudo-alkali ions are based on different scales. Assuming that the ( X-IP) correlations for pseudo-alkali ions constitute the same series as the ( χ-IP) correlations for alkali ions, where X is the electronegativity and IP is the first ionization potential, the electronegativities of Tl +, Ag +, Cu + and Au + are changed to 1.1, 1.3, 1.4 and 1.7, respectively, with noticeable error. The value (1.1) for the Tl + ion is consistent with the ionic character of the bonds formed by Tl + in some compounds.

On the existence of absolute Pauling electronegativities

From a reappreciation of the recently proposed Parr—Pearson scheme on absolute electronegativity and hardness, it follows that electron affinities can be considered as absolute Pauling electronegativities. The fundamental difference between Pauling and Mulliken electronegativities is demonstrated. A quantumchemical framework of Hückel-type is developed wherein these electron affinities act as one-electron energies (diagonal matrix elements). This novel definition of absolute Pauling electronegativities is shown to be consistent with Pauling's original bond energy equation. The validity of the deductions made implies a possible new look at chemical exchange forces in terms of intra-atomic charge-invariance effects (atom—antiatom interactions).

On the pauling electronegativity scales—II

From the analysis of the electrostatic potential near the core-valence boundary in an atom, it is shown that the Pauling electronegativity scale χ p is approximately given by the formula, ▪ where N v is the valence electron number and f( n) is some function of the periodic number in the periodic table. It is also shown in detail that the Pauling electronegativity scale is closely related to the Wang-Parr electronegativity scale which is determined as the negative of the chemical potential in density functional theory. Correlation between the Pauling and Mulliken electronegativities is briefly discussed.

Interpretation of ESCA Chemical Shifts for o-Arylenedioxy Chelates of Silicon

ESCA data on the o-arylenedioxy chelates of silicon have been correlated with data on other organosilicon compounds using PAULING electronegativities. The data do not support p π → d π back bonding in the anionic chelates.

K-absorption spectra and the nature of metal-ligand bond in some cobalt complexes

Shifts and widths of the K-absorption edge of cobalt in a specifically chosen variety and number of complexes involving donor atoms like nitrogen, oxygen and sulphur have been measured using a bent crystal spectrograph. The expected change in ionic/ covalent character of the metal-ligand bond in these complexes on the basis of Pauling's electronegativities and also observed from the optical spectra (where known) appears to be reflected in their X-ray edge-shifts and widths.

Ionicity, atomic radii, and structure in the layered dichalcogenides of group IVb, Vb, and VIb transition metals

Pauling's electronegativities are introduced in considerations of bond lengths, lattice constants, atomic radii, charge densities, structures, and heats of formation of the layered dichalcogenides of Groups IVb, Vb, and VIb transition metals. Strong correlations are found between these and the fractional ionic character of the metal-chalcogen bonds as defined by Pauling. A critical effective radius ratio is defined that separates trigonal prismatic and octahedral compounds.

Empirical relations between σ I, σ oR and taft σ* values of alkyl, acyl, benzoyl and substituted phenyl groups

The X(X) values 1 of the halogens (which resemble the Pauling electronegativities) and of some oxa substituents can be interpreted in terms of the inductive and resonance parameters σ I and σ o R according to the regression equation ▪ and η* R=η(X)−η(R) it is found that for some substituted methyl, phenyl and benzoyl groups [σ*] X R=αη X R where α equals −10.6 and −10.9 for R = Me and R = Ph, CHO and PhCO respectively. Thus [σ*] X Rand η x r represent Taft σ* and [σ I(X)−σ o R(X)] values relative to that of the parent R group. The hydroxyl frequencies of phenol, and benzoic, acrylic, acetic and formic acids measured in dilute carbon tetrachloride solutions correlate with σ I(X) and σ o R(X) according to the equations v(OH) = −423.0 σ I(X) + 3654.7 v(OH) = −270.0 σ 0 R(X) + 3586.7 where X = Ph, PhCO, CH 2=CHCO, MeCO and HCO. From these results, it is inferred that the σ* values of substituents having an α sp 2 hybridized carbon atom are proportional to σ 0 R according to the equation σ*(X) = 3.97 σ 0 R(X) + 1 New σ I σ o R and σ* values of some acyi, benzoyl and substituted phenyl groups are presented.

Use of X-Ray Photoelectron Spectroscopy to Study Bonding in Cr, Mn, Fe, and Co Compounds

The photoelectron spectra of some 40 transition metal compounds have been measured using AlKα(1487 eV) and MgKα(1254 eV) x-rays. The compounds included both simple salts (halides and chalcogenides) and hexacoordinated complexes (cyano- and fluoro-) of Cr(III), Mn(II, III), Fe(II, III), and Co(III). From these data we have determined the chemical shifts of the core electrons and related these results to a calculated charge based on Pauling's electronegativities. In addition, multiplet splitting has been obtained for photoionization in the 3s shell and is discussed in terms of the exchange interaction between the partially filled 3s and 3d orbitals. To help in this explanation, calculations were made using both (1) Hartree-Fock solutions of the wavefunctions for free ions and (2) a qualitative evaluation of the behavior of the exchange integral. The value of using x-ray photoelectron spectroscopy for studying chemical bonding for transition metal compounds is amply illustrated.

NMR-experiments on acetals—part 32 : Dependency of geminal coupling constants of methylene groups on electronegativity, bond length and free orbital overlap of adjacent lobes an empirical relationship as a tool for conformational description

An equation, obtained by iterative fitting of experimental data in some 1,3-diheterocyclic, monocyclic and alicyclic compounds, is proposed. This enables prediction of 2 J(XCH 2Y) as depending on three main contributions: the Pauling electronegativities of X and Y, the bond distances CX and CY and the mutual orientation of the free orbitals and σ(CH) bonds. For the reading of the quantitative contribution to 2 J by the latter phenomenon (p-σ “parallelity effect”) a monogram is presented allowing prediction of the geminal coupling values and conformational discussions in (X,Y-dihetero) cyclic compounds with X and/or Y = S, O, Se, C.

Universal Parameter for the Extrapolation of Force Constants, Mean-Square Quantities, and Bond Energies of Halides

A general formula of the type Y = kω + C, which is simultaneously applicable to force constants, the reciprocals of the mean-square amplitude quantities σr, bond dissociation as well as thermochemical bond energies of halides, has been presented. ω, moreover, is given by the expression ω = 16 | χm − χx | + 3.5(χm − χx)2 + θf, where χm and χx are the Pauling electronegativities of the atoms forming the M–X bond, and where θf is a constant for each of the aformentioned molecular parameters and may have a nonzero value only in the fluorides. The θf values for the three parameters studied were found to be 0, − 11, and − 15 or − 30, respectively. The choice of the latter depends on whether χm > 1 (− 15), or χm ≤ 1(− 30), except for the NaX series for which θf = − 15.

How Inaccurate is Pauling's Bond Energy Equation?

PEARSON1 recently pointed out that Pauling's bond energy equation does not give reasonable values of the enthalpy changes for a series of reactions, and he has also stressed a number of pitfalls of Pauling's electronegativities. The principle of soft and hard acids and bases (SHAB), on the other hand, predicts the correct sign of ΔH for those reactions and the general chemical patterns mishandled by the simple electronegativity concept.

Force Constants and Bond Orders of Nitrogen Bonds

AbstractThe force constants and the corresponding bond orders of nitrogen bonds have been calculated from the vibrational spectra (infrared and Raman spectra) of a great number of nitrogen compounds. Plotting the maximum bond order of stable nitrogen bonds against the sum of Pauling's electronegativities of the bonding partners (Σx) leads to one continuous curve for the NX bonds where X represents elements of the first and the second short period of the periodic table. Furthermore, when the bonds formed between these elements are arranged in a coordinate system in such a way that the position of each bond is determined by the difference between the electronegativities of the bonding partners (Δx along the ordinate) and the sum of the electronegativities of the bonding partners (Σx along the abscissa), the bonding partners capable of forming multiple bonds all lie within a closed domain, where their position can be correlated with their polymerizability and other reactivities of the multiple bonds. Also discussed are the orders of bonds between nitrogen and some transition elements. In an appendix, the present methods used to calculate force constants and bond orders are surveyed.