Structural Importance of Secondary Interactions in Molecules: Origin of Unconventional Conformations of Phosphine-Borane Adducts

Spies, Patrick; Fröhlich, Roland; Kehr, Gerald; Erker, Gerhard; Grimme, Stefan

doi:10.1002/chem.200700649

Cited by 77 publications

(50 citation statements)

References 86 publications

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“…The B-P distance in (F 5 C 6 ) 3 B-PPh 3 is 2.180(6) Å; 5 we predict 2.158 Å, an improvement over the DFT-D-PBE/ TZVP level prediction of 2.22 Å. 6 With this in mind, we note the method predicts a B-P distance of 3.838 Å for (F 5 C 6 ) 3 BP(t-Bu) 3 , some 0.4 Å shorter than that predicted by Pàpai et al 3 Second, the M-P bond distances in the (F 5 C 6 ) 3 B-PR 3 series are nearly identical for R ) Me and Et, increase about 0.1 Å for R ) i-Pr and Ph, and then increase again for R ) t-Bu (substantially for M ) B). This suggests similar steric bulk for i-Pr and Ph substituents, somewhat at odds with their suggested cone angles.…”

Section: Resultsmentioning

confidence: 95%

Donor−Acceptor Dissociation Energies of Group 13−15 Donor−Acceptor Complexes Containing Fluorinated Substituents: Approximate Lewis Acidities of (F₃C)₃M vs (F₅C₆)₃M and the Effects of Phosphine Steric Bulk

Gille

Gilbert

2008

J. Chem. Theory Comput.

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To study donor-acceptor complexes containing fluoroalkyl and -aryl substituents on the acceptors, ONIOM methods for optimizing large complexes and determining single point energies were tested. A two-layer ONIOM optimization procedure utilizing the MPW1K model followed by single point calculations using the composite three-layer ONIOM G2R3 method proved acceptable. The optimization model predicts M-X bond distances well when compared to experiment and shows that the distances increase discontinuously with the bulk of the phosphine. Unexpectedly, (RF)3B-XR3 and (RF)3Al-XR3 bond dissociation energies (ΔEDA) are comparable for several R substituents. For RF = CF3, both are predicted to exhibit M-X ΔEDA values in the range 55-80 kcal mol(-1), exceptionally strong for dative bond energies. For RF = C6F5, the ΔEDA values are predicted to lie in the range 30-45 kcal mol(-1). (F5C6)3BP(t-Bu)3, which does not contain a B-P bond, is predicted to display ΔEDA = 19 kcal mol(-1). The ΔEDA energies do not change smoothly as the steric bulk of the phosphine increases. However, intrinsic ΔEDA energies ΔEint show a regular increase as the donor ability of the phosphine increases, confirming that the reorganization energy of the individual moieties contributes sizably to the overall ΔEDA. The data indicate that PPh3 is approximately equivalent to PMe3 as a donor in terms of ΔEint.

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Section: Resultsmentioning

confidence: 95%

Donor−Acceptor Dissociation Energies of Group 13−15 Donor−Acceptor Complexes Containing Fluorinated Substituents: Approximate Lewis Acidities of (F₃C)₃M vs (F₅C₆)₃M and the Effects of Phosphine Steric Bulk

Gille

Gilbert

2008

J. Chem. Theory Comput.

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“…This implies that the repulsive secondary interaction is more important than the attractive one in this case between these side chains, and suggests that the perfluorophenyl to tertbutyl interaction is not the main governing factor for the characters of the pair. This is in contrast to other phosphine-borane adducts reported by Spies et al with high content of aromatic substitutions, [44] and can be rationalized based on the drastic difference between aromatic-aromatic and aromatic-alkyl dispersion interactions.…”

mentioning

confidence: 71%

Dispersion‐Oriented Soft Interaction in a Frustrated Lewis Pair and the Entropic Encouragement Effect in its Formation

Kim

Rhee

2009

Chemistry A European J

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The origin of the stability of a frustrated Lewis pair (FLP) tBu(3)P:B(C(6)F(5))(3) is investigated computationally to demonstrate the importance of the dispersion interaction. To this end, the interaction between alkyl-substituted phosphines (Me(3)P and tBu(3)P) and hexafluorobenzene (C(6)F(6)) is first investigated. Driven by the lone-pair to pi-orbital interaction, the binding energy is found to be even larger than usual pi-pi interaction energies between small aromatic compounds. This character, which is inherited to fluorophenyl-substituted B(C(6)F(5))(3) in the FLP, induces large flexibility in the FLP over the molecular surface of B(C(6)F(5))(3). This soft interaction, in turn, causes an entropic stabilization of the FLP formation in comparison with classical Lewis pairs based on close and tight P-B dative bonds. It also suggests a diverse nature of the FLP when it is involved in chemical reactions. Even with the cooperative participation of the perfluorophenyl groups, a detailed inspection of the FLP interaction potential energy surface indicates that the boron atom is still the major interaction site for the pair formation. This non-negligible direct P-B interaction, which is related also to the soft nature of the borane frontier orbital, is further supported by substantial spatial overlap between the frontier orbitals on the phosphine/borane fragments and their interaction energy estimations.

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“…These species formed strong intramolecular phosphorus/boron Lewis acid/base adducts. [16,17,18] Studies of the conformational properties revealed heteroalkane-like behavior.…”

Section: Heterolytic Activation Of H 2 By Phosphine/boranementioning

confidence: 99%

Frustrated Lewis Pairs: Metal‐free Hydrogen Activation and More

2009

Self Cite

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Sterically encumbered Lewis acid and Lewis base combinations do not undergo the ubiquitous neutralization reaction to form "classical" Lewis acid/Lewis base adducts. Rather, both the unquenched Lewis acidity and basicity of such sterically "frustrated Lewis pairs (FLPs)" is available to carry out unusual reactions. Typical examples of frustrated Lewis pairs are inter- or intramolecular combinations of bulky phosphines or amines with strongly electrophilic RB(C(6)F(5))(2) components. Many examples of such frustrated Lewis pairs are able to cleave dihydrogen heterolytically. The resulting H(+)/H(-) pairs (stabilized for example, in the form of the respective phosphonium cation/hydridoborate anion salts) serve as active metal-free catalysts for the hydrogenation of, for example, bulky imines, enamines, or enol ethers. Frustrated Lewis pairs also react with alkenes, aldehydes, and a variety of other small molecules, including carbon dioxide, in cooperative three-component reactions, offering new strategies for synthetic chemistry.

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Structural Importance of Secondary Interactions in Molecules: Origin of Unconventional Conformations of Phosphine-Borane Adducts

Cited by 77 publications

References 86 publications

Donor−Acceptor Dissociation Energies of Group 13−15 Donor−Acceptor Complexes Containing Fluorinated Substituents: Approximate Lewis Acidities of (F₃C)₃M vs (F₅C₆)₃M and the Effects of Phosphine Steric Bulk

Donor−Acceptor Dissociation Energies of Group 13−15 Donor−Acceptor Complexes Containing Fluorinated Substituents: Approximate Lewis Acidities of (F₃C)₃M vs (F₅C₆)₃M and the Effects of Phosphine Steric Bulk

Dispersion‐Oriented Soft Interaction in a Frustrated Lewis Pair and the Entropic Encouragement Effect in its Formation

Frustrated Lewis Pairs: Metal‐free Hydrogen Activation and More

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Structural Importance of Secondary Interactions in Molecules: Origin of Unconventional Conformations of Phosphine-Borane Adducts

Cited by 77 publications

References 86 publications

Donor−Acceptor Dissociation Energies of Group 13−15 Donor−Acceptor Complexes Containing Fluorinated Substituents: Approximate Lewis Acidities of (F3C)3M vs (F5C6)3M and the Effects of Phosphine Steric Bulk

Donor−Acceptor Dissociation Energies of Group 13−15 Donor−Acceptor Complexes Containing Fluorinated Substituents: Approximate Lewis Acidities of (F3C)3M vs (F5C6)3M and the Effects of Phosphine Steric Bulk

Dispersion‐Oriented Soft Interaction in a Frustrated Lewis Pair and the Entropic Encouragement Effect in its Formation

Frustrated Lewis Pairs: Metal‐free Hydrogen Activation and More

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Donor−Acceptor Dissociation Energies of Group 13−15 Donor−Acceptor Complexes Containing Fluorinated Substituents: Approximate Lewis Acidities of (F₃C)₃M vs (F₅C₆)₃M and the Effects of Phosphine Steric Bulk

Donor−Acceptor Dissociation Energies of Group 13−15 Donor−Acceptor Complexes Containing Fluorinated Substituents: Approximate Lewis Acidities of (F₃C)₃M vs (F₅C₆)₃M and the Effects of Phosphine Steric Bulk