Extending Molecular Mechanics Methods to the Descriptions of Transition Metal Complexes and Bond-Making and -Breaking Processes

Landis, Clark R.; Firman, Timothy K.; Cleveland, T.K.; Root, Daniel M.

doi:10.1007/978-94-011-5171-9_3

Cited by 9 publications

(1 citation statement)

References 51 publications

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“…NRT evaluations thereby complement and extend conventional NBO second-order E DA (2) perturbative analysis, and can be used even when the latter descriptors are unavailable (i.e., higher-level correlated wavefunctions, where no available 1-electron effective Hamiltonian operator of Fock or Kohn–Sham type provides orbital energetics). NRT evaluations are also fully consistent with the general 3c/4e ionic-resonance picture of main-group hypervalency and metallic-like long-bonding, as well as the corresponding “12-electron rule” extensions of localized hybridization, bonding, and resonance concepts in transition metal chemistry …”

Section: Alternative “Natural” Path To Localized Lewis and Resonance ...supporting

confidence: 68%

Resonance Theory Reboot

2019

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What is now called "resonance theory" has a long and conflicted history. We first sketch the early roots of resonance theory, its heritage of diverse physics and chemistry conceptions, and its subsequent rise to reigning chemical bonding paradigm of the mid-20th century. We then outline the alternative "natural" pathway to localized Lewis-and resonance-structural conceptions that was initiated in the 1950s, given semi-empirical formulation in the 1970s, recast in ab initio form in the 1980s, and successfully generalized to multi-structural "natural resonance theory" (NRT) form in the 1990s. Although earlier numerical applications were often frustrated by the ineptness of then-available numerical solvers, the NRT variational problem was recently shown to be amenable to highly efficient convex programming methods that yield provably optimal resonance weightings at a small fraction of previous computational costs. Such convexity-based algorithms now allow a full "reboot" of NRT methodology for tackling a broad range of chemical applications, including the many familiar resonance phenomena of organic and biochemistry as well as the still broader range of resonance attraction effects in the inorganic domain. We illustrate these advances for prototype chemical applications, including (i) stable near-equilibrium species, where resonance mixing typically provides only small corrections to a dominant Lewisstructural picture, (ii) reactive transition-state species, where strong resonance mixing of reactant and product bonding patterns is inherent, (iii) coordinative and related supramolecular interactions of the inorganic domain, where sub-integer resonance bond orders are the essential origin of intermolecular attraction, and (iv) exotic longbonding and metallic delocalization phenomena, where no single "parent" Lewis-structural pattern gains pre-eminent weighting in the overall resonance hybrid.

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Section: Alternative “Natural” Path To Localized Lewis and Resonance ...supporting

confidence: 68%