A Bonding Quandary—or—A Demonstration of the Fact That Scientists Are Not Born With Logic

Álvarez, Santiago; Hoffmann, Roald; Mealli, Carlo

doi:10.1002/chem.200900239

Cited by 81 publications

(80 citation statements)

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“…Or maybe it has done so well precisely because the concept is flexible and fuzzy". [16] However, it is important to note that scientific arguments, debates, and controversies are at the heart of chemistry. This situation has been clearly stated in the very recent paper entitled "The Nature of the Fourth Bond in the Ground State of C 2 : The Quadruple Bond Conundrum" by Danovich et al, [17] in which these authors recongnize that they are in front of a "Rashomon effect", in which the bonding picture is becoming too fuzzy to be constructive anymore.…”

Section: Introductionmentioning

confidence: 99%

A Complete NCI Perspective: From New Bonds to Reactivity

Narth¹,

Maroun²,

Boto³

et al. 2016

Challenges and Advances in Computational Chemistry and Physics

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The Non-Covalent Interaction (NCI) index is a new topological tool that has recently been added to the theoretical chemist's arsenal. NCI fills a gap that existed within topological methods for the visualization of non-covalent interactions. Based on the electron density and its derivatives, it is able to reveal both attractive and repulsive interactions in the shape of isosurfaces, whose color code reveals the nature of the interaction. It is interesting to note that NCI can even be calculated at the promolecular level, making it a suitable tool for big systems, such as proteins or DNA. Within this chapter we will review the main characteristics of NCI, its similarities with and differences from previous approaches. Special attention will be paid to the visualization of new interaction types. Being based on the electron density, NCI is not only very stable with respect to the calculation method, but it is also a suitable tool for detecting new bonding mechanisms, since all such mechanisms should have a detectable effect on the electron density. This type of approach overcomes the limitations of bond definition, revealing all interaction types, irrespective of whether they have a name or have previously been identified. Finally, we will show how this tool can be used to understand chemical change along a chemical reaction. We will show several examples of torquoselectivity and put forward an explanation of selectivity based on secondary interactions which is complementary to the historical orbital approach.A complete NCI perspective: from new bonds to reactivity 3

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Section: Introductionmentioning

confidence: 99%

A Complete NCI Perspective: From New Bonds to Reactivity

Narth¹,

Maroun²,

Boto³

et al. 2016

Challenges and Advances in Computational Chemistry and Physics

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“…Of primary concern to the Alvarez-Hoffmann-Mealli (AHM) argument is the question of whether or not a transmolecular S À S bond exists in 1, a question that has not yet received a definitive answer. [1,3,4] This stirred my enthusiasm, because the gray area between what is to be considered a chemical bond and what is not is one of great interest to me.…”

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confidence: 96%

“…Recently, this journal published a lively debate [1] between Santiago Alvarez, Roald Hoffmann, and Carlo Mealli about the electronic structure of a trigonally symmetric complex with a {Cu 3 S 2 } 3 + core (1) shown in Figure 1, which was first synthesized by the Tolman group. [2] This complex is not only an interesting model for biologically important coppersulfur clusters, but also poses inherent problems in its electronic structure and its relationship to the salient structural and magnetic features of the compound.…”

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confidence: 99%

A Definitive Answer to a Bonding Quandary? The Role of One‐Electron Resonance Structures in the Bonding of a {Cu₃S₂}³⁺ Core

Berry

2010

Chemistry A European J

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A propargylic ester containing a propargylic alkoxy group has been observed to preferentially undergo [1,2]‐acyl shift over [1,3]‐shift. In addition, the complementary and contrasting reactivity of vinyl vs. alkynyl platinum carbenoids has been discovered. Vinyl platinum carbenoids are more prone to undergo [1,2]‐H shift over addition to π‐bonds whereas alkynyl platinum carbenoids preferentially add to π‐bonds.

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“…None of them are unambiguous, however, and different analyses can lead to conflicting interpretations, even concerning the most fundamental question of whether or not atoms are linked by a chemical bond. [1,2] One of the indicators that can be probed experimentally is the indirect spin-spin coupling constant (SSCC). For instance, observation of spinspin coupling across hydrogen bonds [3] has been taken as evidence for covalent contributions to this kind of bonding.…”

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confidence: 99%

Weak Te,Te Interactions through the Looking Glass of NMR Spin–Spin Coupling

et al. 2013

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Most of the tools for quantifying the extent of chemical bonding between two atoms are quantum-chemical in nature. None of them are unambiguous, however, and different analyses can lead to conflicting interpretations, even concerning the most fundamental question of whether or not atoms are linked by a chemical bond. [1,2] One of the indicators that can be probed experimentally is the indirect spin-spin coupling constant (SSCC). For instance, observation of spinspin coupling across hydrogen bonds [3] has been taken as evidence for covalent contributions to this kind of bonding. For atoms within the same molecule that are close in space, but not linked through a direct formal bond, the question arises, how much of the observed coupling is transmitted through a succession of bonds that eventually links them ("through-bond coupling"), and how much is due to interaction through the overlap of lone pairs ("through-space coupling"). Again, a variety of quantum-chemical tools have been developed to address this question.A rigid scaffold that is used to achieve such spatial proximity is the naphthalene framework, in which substituents in the peri (1,8) positions have a typical separation of around 3 . [4] Through-space J( 19 F, 19 F) SSCCs, long known for their distance dependence, [5a] have been studied in some detail in peri-difluoronaphthalenes. [5b,c] Similarly, J( 31 P, 31 P) values in peri-bis(phosphino)naphthalenes have been attributed to through-space coupling, [6] and J( 77 Se, 77 Se) values in peri-bis(seleno) derivatives have been analyzed in detail through quantum-chemical computations. [7] In systematic studies of naphthalene (N) and acenaphthene (A) derivatives with pnictogen and chalcogen atoms in the peri positions, it became apparent that for the heavier congeners, steric repulsion is partly counterbalanced by attractive interactions. In particular with Te substituents, formally nonbonded, "across-the-bay" distances are significantly shorter than the sum of the van-der-Waals radii, which has been traced back to weak donor-acceptor interactions and the onset of 3-center-4-electron (3c4e) bonding. [8] For instance in N1 and A1 (Scheme 1), Te···Te distances of around 3.3 are observed in the solid state (ca. 0.7 below the sum of the vdW radii), and Wiberg bond indices [9] (WBIs, a measure for the covalent character of a bond, approaching WBI = 1 for a true single bond) of around 0.15 have been computed. Slightly larger WBIs of approximately 0.18 have been obtained for cationic methylated species N2 and A2, despite a slightly longer Te-Te separation (ca. 3.4 ). [10] These unsymmetrical systems show remarkably large J( 125 Te, 125 Te) SSCCs, formally 4 J values, of 1093.0 Hz and 945.8 Hz in N2 and A2, respectively. [10] We now report even larger couplings in N1 and A1, along with computational conformational analysis underlining the potential of this property as a structural and interpretative method.The computed (ZORA-SO/BP//B3LYP level) [11] J( 125 Te, 125 Te) SSCCs in N2 and A2 (1490 and 1377 Hz, respec...

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A Bonding Quandary—or—A Demonstration of the Fact That Scientists Are Not Born With Logic

Cited by 81 publications

References 73 publications

A Complete NCI Perspective: From New Bonds to Reactivity

A Complete NCI Perspective: From New Bonds to Reactivity

A Definitive Answer to a Bonding Quandary? The Role of One‐Electron Resonance Structures in the Bonding of a {Cu₃S₂}³⁺ Core

Weak Te,Te Interactions through the Looking Glass of NMR Spin–Spin Coupling

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A Bonding Quandary—or—A Demonstration of the Fact That Scientists Are Not Born With Logic

Cited by 81 publications

References 73 publications

A Complete NCI Perspective: From New Bonds to Reactivity

A Complete NCI Perspective: From New Bonds to Reactivity

A Definitive Answer to a Bonding Quandary? The Role of One‐Electron Resonance Structures in the Bonding of a {Cu3S2}3+ Core

Weak Te,Te Interactions through the Looking Glass of NMR Spin–Spin Coupling

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A Definitive Answer to a Bonding Quandary? The Role of One‐Electron Resonance Structures in the Bonding of a {Cu₃S₂}³⁺ Core