Energy decomposition analysis Zhao, Lili; von Hopffgarten, Moritz; Andrada, Diego M. ...
Wiley interdisciplinary reviews. Computational molecular science,
May/June 2018, Letnik:
8, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The energy decomposition analysis (EDA) is a powerful method for a quantitative interpretation of chemical bonds in terms of three major components. The instantaneous interaction energy ΔEint between ...two fragments A and B in a molecule A–B is partitioned in three terms, namely (1) the quasiclassical electrostatic interaction ΔEelstat between the fragments; (2) the repulsive exchange (Pauli) interaction ΔEPauli between electrons of the two fragments having the same spin, and (3) the orbital (covalent) interaction ΔEorb which comes from the orbital relaxation and the orbital mixing between the fragments. The latter term can be decomposed into contributions of orbitals with different symmetry which makes it possible to distinguish between σ, π, and δ bonding. After a short introduction into the theoretical background of the EDA we present illustrative examples of main group and transition metal chemistry. The results show that the EDA terms can be interpreted in chemically meaningful way thus providing a bridge between quantum chemical calculations and heuristic bonding models of traditional chemistry. The extension to the EDA–Natural Orbitals for Chemical Valence (NOCV) method makes it possible to breakdown the orbital term ΔEorb into pairwise orbital contributions of the interacting fragments. The method provides a bridge between MO correlations diagrams and pairwise orbital interactions, which have been shown in the past to correlate with the structures and reactivities of molecules. There is a link between frontier orbital theory and orbital symmetry rules and the quantitative charge‐ and energy partitioning scheme that is provided by the EDA–NOCV terms. The strength of the pairwise orbital interactions can quantitatively be estimated and the associated change in the electronic structure can be visualized by plotting the deformation densities.
This article is categorized under:
Structure and Mechanism > Molecular Structures
Electronic Structure Theory > Density Functional Theory
Computer and Information Science > Visualization
First column: Plot of the deformation densities Δρ1–4 with associated stabilization energies ΔE1–4 of the four most important orbital interactions in B2(NHCMe)2. The color code for the charge flow is red→light blue. Third and fourth column: Plot of the interacting donor and acceptor orbitals and calculated eigenvalues ε of (NHCMe)2 and (1Σg+) B2. Second column: Resulting MOs of the complex B2(NHCMe)2.
Quantum chemical calculations have been carried out at the BP86/TZ2P+ level for the compounds SiC(L)2 with L=NHCMe, CAACMe, PMe3 (NHC=N‐heterocyclic carbene, CAAC=cyclic (alkyl)aminocarbene). The ...optimized geometries exhibit a trans arrangement of the ligands L at SiC with a planar coordination when L=NHCMe and PMe3, while a twisted conformation is calculated when L=CAACMe. The bending angle L‐Si‐C is significantly more acute than the angle L‐C‐Si. Both angles become wider with the trend PMe3<NHCMe<CAACMe. The latter trend is also found for the bond dissociation energies of the reaction SiC(L)2→SiC+2 L, which have absolute values between De=98–163 kcal mol−1. Calculations suggest that the compounds SiC(L)2 have a very large first and second proton affinity, which takes place at the central carbon and silicon atoms, respectively. Energy decomposition analyses indicate that the best description of the bonding situation in SiC(L)2 features a cumulenic carbon–carbon bond and a dative carbon–silicon bond LCSi←L at the center.
Planar or twisted? Quantum‐chemical calculations have been carried out at the BP86/TZ2P+ level for the compounds SiC(L)2 (L=NHCMe, CAACMe, PMe3; NHC=N‐heterocyclic carbene, CAAC=cyclic (alkyl)aminocarbene). The optimized geometries exhibit a trans arrangement of the ligands L at SiC with a planar coordination when L=NHCMe and PMe3, while a twisted conformation is calculated when L=CAACMe (see structures; Si crimson, P pink, N blue).
A summary of theoretical and experimental work in the area of low-coordinated compounds of boron and group-14 atoms C-Sn in the last decade is presented. The focus of the account lies on molecules EL
...2
, E
2
L
2
and E
3
L
3
, which possess dative bonds between one, two or three atoms E and σ-donor ligands L that stabilize the atoms E through L→E donor-acceptor interactions. The interplay between theory and experiment provides detailed insight into the bonding situation of the molecules, which serves as guideline for the synthesis of molecules that possess unusual bonding motifs.
Donor-acceptor complexes of one, two or three atoms E = B, Si-Sn which are stabilized by σ-donor ligands L are discussed.
Here, we discuss that unlike bond dissociation energy (BDE) that is a state function quantity, the energy components of the energy decomposition analysis (EDA),
i.e.
electrostatic interaction, Pauli ...repulsion, and orbital interaction, are path (process) function quantities. Being a path function means that EDA energy components are not uniquely defined,
i.e.
the relative magnitudes of the orbital interaction, Pauli repulsion, and electrostatic components may vary depending on the selected pathway for EDA. Therefore, at best, EDA can define whether closely related chemical bonds are more or less ionic/covalent compared with each other. However, a precise assessment of the nature of a certain type of chemical bond using EDA is a questionable task. Besides, we briefly discuss that the widely used EDA pathway, which is merely an arbitrary choice among infinite possible paths, comes to conclusions not consistent with our widely accepted knowledge of bond formation even for the simplest molecules.
EDA energy components are path functions. Is there any preferred path for EDA?
The BP unsaturated unit is a very attractive functional group as it provides novel reactivity and unique physical properties. Nonetheless, applications remain limited so far due to the bulky nature ...of B/P‐protecting groups, required to prevent oligomerization. Herein, we report the synthesis and isolation of a N‐heterocyclic carbene (NHC)‐stabilized phosphaborene, bearing a trimethylsilyl (TMS) functionality at the P‐terminal, as a room‐temperature‐stable crystalline solid accessible via facile NHC‐induced trimethylsilyl chloride (TMSCl) elimination from its phosphinoborane precursor. This phosphaborene compound, bearing a genuine B=P bond, exhibits a remarkable ability for undergoing P‐centre metathesis reactions, which allows the isolation of a series of unprecedented phosphaborenes. X‐ray crystallographic analysis, UV/Vis spectroscopy, and DFT calculations provide insights into the B=P bonding situation.
Stable compounds with a genuine B=P double bond are rare and have limited applications given their protecting groups′ bulky nature. The preparation of a Lewis base‐stabilized phosphaborene with a B=P double bond and a trimethylsilyl (TMS) functionality at the P‐terminal is reported, which exhibits an unprecedented ability for B=P‐unit transfer reactions, allowing the isolation of B=P‐containing compounds.
Although silylene‐carbonyl complexes are known for decades, only recently isolable examples have been accomplished. In this work, the bonding situation is re‐evaluated to explain the origins of their ...remarkable stability within the Kohn‐Sham molecular orbital theory framework. It is shown that the chemical bond can be understood as CO interaction with the silylene via a donor‐acceptor interaction: a σ‐donation from the σCO into the empty p‐orbital of silicon, and a π‐back donation from the sp2 lone pair of silicon into the π*CO antibonding orbitals. Notably, it was established that the driving force behind the surprisingly stable Si−CO compounds, however, is another π‐back donation from a perpendicular bonding R−Si σ‐orbital into the π*CO antibonding orbitals. Consequently, the pyramidalization of the central silicon atom cannot be associated with the strength of the π‐back donation, in sharp contrast to the established chemical bonding model. Considering this additional bonding interaction not only shed light on the bonding situation, but is also an indispensable key for broadening the scope of silylene‐carbonyl chemistry.
Revisiting the chemical bond on silylene‐carbonyl species reveals a donor‐acceptor interaction between the CO and the silylene. The bonding can be conventionally understood as a σ‐donation from the σCO into the empty p‐orbital of silicon, and a π‐back donation from the sp2 lone pair of silicon into the π*CO antibonding orbitals. Nonetheless, an unrecognized π‐back‐donation from the R−Si σ‐orbital into the π*CO antibonding orbital faithfully explains the relationship between structure and stability.
Quantum chemical calculations using ab initio methods at the CCSD(T)/def2-TZVPP level and density functional theory using BP86 and M06-2X functionals in conjunction with def2-TZVPP basis sets have ...been carried out on the title molecules. The calculated energies suggest that the N-oxides R3NO with R = F, Cl are lower in energy than the amine isomers R2NOR, but the latter form is more stable than the N-oxides when R = H, Me, Ph. In contrast, the phosphane oxides R3PO are always more stable than the phosphanyl isomers R2NOR except for the parent system with R = H, where the two isomers are close in energy. The energy decomposition analysis suggests that the best description of the N–O bond in N-oxides R3NO depends on the nature of the substituent R. The halogen systems F3NO and Cl3NO and the triphenyl species Ph3NO possess dative bonds R3N→O, which are enhanced by R3N←O π backdonation. The contribution of the π backdonation is only 10% of the total orbital interactions ΔEorb in Ph3NO, but it amounts to ∼22% of ΔEorb in F3NO and Cl3NO. The N–O bonds H3NO and Me3NO are better described in terms of electron-sharing single bonds between charged fragments R3N+–O−, which are supported by modest R3N+←O− π backdonation that comprise 13–16% of ΔEorb. In contrast, all phosphane oxides R3PO are best depicted with electron-sharing single bonds between charged fragments R3P+–O−, which are significantly supported by R3P+←O− π backdonation contributing 22–32% of ΔEorb.
Stable Silapyramidanes Imagawa, Taiki; Giarrana, Luisa; Andrada, Diego M. ...
Journal of the American Chemical Society,
03/2023, Letnik:
145, Številka:
8
Journal Article
Recenzirano
Starting from tetrakis(trimethylsilyl)cyclobutadiene and an amidinate-supported silylene of the Roesky-type, a sequence of addition and reduction cleanly gives the elusive silapyramidane via an ...isolable cyclobutene intermediate with an exocyclic SiC bond. The silapyramidane features an unusually shielded 29Si NMR resonance at −448.3 ppm for the apex silicon atom. Treatment with Fe2(CO)9 results in the formation of the corresponding silapyramidane–iron complex. Silapyramidane also reacts with the cyclobutadiene starting material to cleanly afford a fluorescent spirobis(silole).
Chemical bonds are traditionally assigned as electron‐sharing or donor‐acceptor/dative. External criteria such as the nature of the dissociation process, energy partitioning schemes, or quantum ...chemical topology are invoked to assess the bonding situation. However, for systems with marked multi‐reference character, this binary categorization might not be precise enough to render the bonding properties. A third scenario can be foreseen: spin polarized bonds. To illustrate this, the case of a NaBH3− cluster is presented. According to the analysis NaBH3− exhibits a strong diradical character and cannot be classified as either electron‐sharing or a dative bond. Elaborated upon are the common problems of popular bonding descriptions. Additionally, a simple model, based on the bond order and local spin indicators, which discriminates between all three bonding situations, is provided.
Conventional chemical bonding analysis distinguishes between two situations: electron sharing and donor‐acceptor. However, a third scenario is possible where the bond suffers spin polarization. Discussed here is the case of NaBH3−, better classified as a spin‐polarized bond. A simple model to distinguish between these bonding types is provided.
The Bonding Situation in Metalated Ylides Scharf, Lennart T.; Andrada, Diego M.; Frenking, Gernot ...
Chemistry,
March 28, 2017, Letnik:
23, Številka:
18
Journal Article
Recenzirano
Odprti dostop
Quantum chemical calculations have been carried out to study the electronic structure of metalated ylides particularly in comparison to their neutral analogues, the bisylides. A series of compounds ...of the general composition Ph3P−C−L with L being either a neutral or an anionic ligand were analyzed and the impact of the nature of the substituent L and the total charge on the electronics and bonding situation was studied. The charge at the carbon atom as well as the dissociation energies, bond lengths, and Wiberg bond indices strongly depend on the nature of L. Here, not only the charge of the ligand but also the position of the charge within the ligand backbone plays an important role. Independent of the substitution pattern, the NBO analysis reveals the preference of unsymmetrical bonding situations (P=C−L or P−C=L) for almost all compounds. However, Lewis structures with two lone‐pair orbitals at the central carbon atom are equally valid for the description of the bonding situation. This is confirmed by the pronounced lone‐pair character of the frontier orbitals. Energy decomposition analysis mostly reveals the preference of several bonding situations, mostly with dative and ylidic electron‐sharing bonds (e.g., P→C−−L). In general, the anionic systems show a higher preference of the ylidic bonding situations compared to the neutral analogues. However, in most of the cases different resonance structures have to be considered for the description of the “real” bonding situation.
Dative or not? The bonding situation in metalated ylides (L=anionic, see scheme) and their related bisylides was examined by DFT calculations. Dative, ylidic, and double bonds can be formed depending on the substitution pattern and the total charge of the compounds. In general, several resonance structures contribute to the “real” bonding situation, which in turn can be tailored by careful selection of L.
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