Bond-valence summation for borates

Donnay, Gabrielle; Donnay, J. D. H.

doi:10.1107/s0567740873004668

Cited by 41 publications

(13 citation statements)

References 7 publications

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“…Several authors [5][6][7][103][104][105][106][107][108] -to identify oxygen atoms which constitute an OH group or H20 molecule in minerals [6,105,106,110] and polyoxometalate ions [10,11,101,111] via a corresponding deviation of the calculated sum of the bond valences from the bond valence two expected for oxygen; -to control the validity of interpretations of crystal structure investigations [6,7,106,109,110]; -to elucidate the hydrogen bridge system of polyoxometalates [8][9][10][11][12][13] and other compounds [6,7,105,106,109]; -to determine the charge (oxidation number) of the M atoms [5,7,107,109,110]; -to control the coordination numbers assigned to the central atoms of coordination polyhedra [5-7, 105-107, 1 l 1], and others [5-7, 107, 109, 110].…”

Section: Test Of the Bond Modelmentioning

confidence: 99%

“…1). In terms of our bond model, the authors [119] could have considered the resonance types (5), (6), and (8). However, a more detailed analysis of the polyoxometalate structures as described in Sects.…”

Section: Application Of Valence Bond Formalismsmentioning

confidence: 99%

“…1The terms "bond valence", "bond strength", "bond order", and other terms are not uniformly used in the literature [5][6][7]. In this article bond order is used to indicate the number of bonds between two atoms in a classical formula (in one of the resonance formulae), whereas bond valence is used to characterize the weighted mean of the bond orders of a bond considered in the different resonance formulae or to characterize a bond according to Eqs.…”

Section: Introductionmentioning

confidence: 99%

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A bond model for polyoxometalate ions composed of MO6 octahedra (MOk polyhedra with k>4)

Tytko¹

Structure and Bonding

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The literature relating to the bonding in polyoxometalate ions is reviewed. The author's opinions are presented and expanded to give a bond model for polyoxometalate ions of the early transition elements (groups V and VI) composed of MO 6 octahedra (MOk polyhedra with k > 4). This bond model concerns in particular the bond valence (bond lengths) and charge distribution in the polyoxometalate ions and the factors modifying them. It is based on the following commonly used concepts and principles as applied to polyoxometalate ions: -Lewis's octet rule, extended to the decet and dodecet rule for M v and MVI; -prc-drc M----O double bond and the coordinate bond (dative bond); -the resonance concept; -the resonance bond number (or the bond valence concept and the valence sum rule); -polydentate ligands and the chelate effect; -the larger space requirements of unshared electron pairs (cf. the VSEPR model); -the model of multicenter prc-drc multiple bonds for certain #-oxo bridges between metal atoms; -Bronsted's acid/base concept and acid/base equilibria; -Pauling's rules for the acid/base strength of (monomeric) oxoacids/oxoanions; -the law of mass action (Le Chatelier's principle), and others. The result is a set of resonance structures for polyoxometalate species in which three types of resonance can be distinguished. These, in turn, explain: -the cohesion of the strongly distorted tetrahedral M04 building units in the structures by formation of MO 6 octahedra and hence the enhanced stability of the polyoxometalate ions; -the distribution of the formal ionic charge over (nearly) all types of oxygen atoms, but preferably the terminal ones; -the occurrence of positively charged oxygen atoms, caused by charge separation processes; -the enhanced basicity of polyoxometalate ions; and further features. A "meshing effect" defines the increase of the bond valence in inner (bridging) M-O bonds and hence the stabilization of the structures due to extension of the coordination spheres of MO4 tetrahedra. Thus, the bond lengths of the different structure types are governed by a maximization of the bond valence of the inner, bridging (or minimization of the bond valence of the outer, terminal, in contrast to frequent statements in the literature) M-O bonds. The limits of the maximization of the inner bond valences of the polyoxometalate ions are determined -by minimum stoichiometric requirements for corresponding resonance formulae (inevitability of charge on bridging oxygen atoms); -by the necessity to fulfill simultaneously the geometrical relationships of the M-O bond lengths (as defined by their interdependence in the M-O frameworks) and the valence

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Section: Test Of the Bond Modelmentioning

confidence: 99%

Section: Application Of Valence Bond Formalismsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A bond model for polyoxometalate ions composed of MO6 octahedra (MOk polyhedra with k>4)

Tytko¹

Structure and Bonding

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“…It is determined from structure data, which are derived from diffraction experiments, spectroscopy, or quantumchemical calculations. To distinguish clearly between these two types of valencies, the descriptive terms stoichiometric valence and structural valence and the respective symbols Keywords: bond theory · oxidation · stoichiometric valence · structural valence · valence corresponding logarithmic correlations hold also for heteroatomic bonds, [13,14] Brown and Altermatt [15] used Pauling's empirical logarithmic relationship in the form of the exponential equation [Eq. (2)].…”

Section: The Bond-valence Modelmentioning

confidence: 99%

Stoichiometric Valence and Structural Valence—Two Different Sides of the Same Coin: “Bonding Power”

Liebau

Wang

Liebau

2009

Chemistry A European J

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Recent studies use the term valence to describe two distinct aspects of the phenomenon bonding power of an atom. Measured in valence units, one valence term, the classical chemical valence, has integer values and is derived solely from the composition of a compound. The second one, used mainly by solid-state physicists and crystallographers, has non-integer values. It is determined from structure data, which are derived from diffraction experiments, spectroscopy, or quantum-chemical calculations. To distinguish clearly between these two types of valencies, the descriptive terms stoichiometric valence and structural valence and the respective symbols (stoich)V and (struct)V should be used. For the majority of crystalline structures, values of (stoich)V and (struct)V, both measured in valence units, differ by less than 5%. However, for p-block atoms with one lone electron pair, differences between (stoich)V and (struct)V of up to 30% have been reported.

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“…(la) and (lb)), based on a relationship proposed by Pauling [12], led to a considerable improvement of the concept. The terms 'bond strength', 'bond order', and other terms that were used at that time have been changed to 'bond valence' [3,8,10,13,14] since bond strength and bond order are terms also used in a different sense. The parameters of the bond length-bond valence functions have been determined for a large number of bond partners [4,8,9,[15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Bond length-bond valence relationships with particular reference to polyoxometalate chemistry

Tytko

Mehmke

Kurad

Structure and Bonding

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Bond length-bond valence relationships have been investigated fundamentally with emphasis on the M-O bonds in polyoxo compounds (M = MoVI,wVl,VV,NbV, TaV). A large number of errors of different types has been made in the derivation of practically all of the published functions and/or of the relevant parameters. Considering all sources of errors, bond length-bond valence functions and the relevant parameters have been derived which represent more shallow curves than most of the functions in the literature. The relationships have been applied classically for identifying O atoms of an OH group or a coordinated H20 molecule, to elucidate hydrogen bridge systems, to determine the oxidation numbers of M atoms (and to distinguish between different elements via the oxidation numbers), and to verify the coordination numbers assigned to the M atoms, etc. The most important application of the relationship, however, is the calculation of accurate bond valences and in particular the determination of the distribution of the charge over the O atoms of the species. These data can be used to elucidate the relationships between structure, bonding, stability and basicity of the species. However, most functions and/or the relevant parameters stated in the literature produce errors which are most evident in the calculated formal ionic charges of the species and can involve several charge units. Even the best functions and parameters give unreliable results. A first important reason for this is the unsatisfactory identification of erroneous structural data with large random and/or systematic errors in the bond lengths and their rejection from the set of reference structures used for the derivation of the bond length-bond valence parameters B and do or N and do of the commonly used exponential or power functions. This makes the correct determination of B or N difficult. A second important reason is connected with the -at present -unfounded practice of using 'universal' B or N parameters which leads to errors for the proportion in the bond valencies of the inner (bridging) relative to those in the outer (terminal) M-O bonds of the species and for the charge separations. These quantities affect the stability of the species. A third significant reason, which is independent of and hence present even for correctly derived bond length-bond valence parameters, is a small (and inevitable) systematic error in the bond lengths of each structure determination which leads to larger errors for the formal ionic charge. This error can be completely compensated by individual fitting of the do bond length-bond valence parameter for each structural determination.

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Bond-valence summation for borates

Abstract: In constructing the table of bond-valence balance for fl-HBO2, Zachariasen [Aeta Cryst. (1963)

Cited by 41 publications

References 7 publications

A bond model for polyoxometalate ions composed of MO6 octahedra (MOk polyhedra with k>4)

A bond model for polyoxometalate ions composed of MO6 octahedra (MOk polyhedra with k>4)

Stoichiometric Valence and Structural Valence—Two Different Sides of the Same Coin: “Bonding Power”

Bond length-bond valence relationships with particular reference to polyoxometalate chemistry

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