Natural Bond-Order Analysis

Natural bond order analysis (NBO) is the name of a whole set of analysis techniques. One of these is the natural population analysis (NPA) for obtaining 

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Several alternatives to the Mulliken population have been presented that attempt to provide more rigorous estimates of the charges on atoms in molecules or clusters although not all have been applied in chemisorption and catalysis. We quote the Natural Bond Order analysis, and the elegant topological analysis of the electron density or of the electron localization function, ELF, introduced by Becke and Edgecombe. " ELF analysis has... 

Beryllium-silicon bonds are a recent development. They are likewise prepared by the reaction of the metal halide with alkali metal silyls, but unlike the Mg analogues, both of the well-characterized Be examples are base-free. While [(te/T-Bu3Si)BeCl] is oligomeric, the molecular structure of (tert-Bu3Si)2Be features a perfectly linear Si-Be-Si unit. CpBe(SiMe3), prepared from CpBeCl and trimethylsilyllithium in pentane, exhibits an intriguing thermal chemistry. The identity of the primary thermolysis products, Scheme 14, implies the participation of silylene intermediates, a contention supported by DFT/NBO (density functional theory/natural bond order) analysis. ... 

NBO (natural bond order) the name of a set of population analysis techniques NDO (neglect of differential overlap) the fundamental assumption behind many semiempirical methods... 

The Natural Bond Orbital analysis of Weinhold [Foster and Weinhold, 1980 Reed, Weinstock etal., 1985 Reed, Curtiss etal., 1988] generates, departing from canonical MOs, a set of localized one center (core, lone pairs) and two center (jt and a bonds) strongly occupied orbitals, and a set of one center (Rydberg) and two center (a, Jt ) weakly occupied orbitals the NBOs. The Natural Bond Orbitals (NBOs) are obtained by a sequence of transformations from the input basis to give, first, the Natural Atomic Orbitals (NAOs), then the Natural Hybrid Orbitals (NHOs), and finally the Natural Bond Orbitals (NBOs). For NAOs, atomic charges can be calculated as a summation of contributions given by orbitals localized on each atom moreover, from NBOs, bond order can be also calculated. 

Ma3T s equation. Note that theoretical electrophilicities are obtained from the isolated ground state of molecules. In the next section, we consider this point by examining the electrophile-nucleophile interaction using a natural bond order population analysis. 

A computational study has been carried out on the model eomplexes Ni2(HC=CH)2(NH3)2, Ni2(HG=GH)3, Ni3(HG=GH)4, and (GpNi)2(/x-HG=GH) in an effort to describe the Ni-alkyne bonding in homoleptic Ni (alkyne) +i complexes. " The natural bond order population analysis carried out by DFT methods has shown that dinuclear Ni(0)-alkyne complexes are stabilized by the delocalization of electron density from the filled 3d-orbitals of one Ni into empty 4j--orbitals of the other. The strength of this Ni(< )-Ni( / ) interaction varies among the models studied (ca. 26-66 kj mol ) becoming weaker upon formation of additional bridging alkynes. 

Scheme 4.34) [108]. According to the experimentally determined bond lengths, a natural bond orbital (NBO) bond order analysis and the calculated nucleus-independent chemical shifts (NICSs), the bowl-shaped circulene 158 can be considered as a fourfold benzoannulated [4] radialene, not a fourfold napthoannulated cyclobutadiene. 

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