Stereoelectronic Effects of the Group 4 Metal Substituents in Organic Chemistry

White, Jonathan M.; Clark, Christopher I.

doi:10.1002/9780470147313.ch3

Cited by 20 publications

(12 citation statements)

References 197 publications

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“…It is well established that such donors as C–Si, C–Ge, and C–Sn bonds are capable of providing significant stabilization to a developing positive charge . For example, Lambert and coworkers reported that axial trimethylsilyl substitution can lead 10 rate enhancements upon elimination of axial leaving groups (Figure ) .…”

Section: Factors Controlling Hyperconjugationmentioning

confidence: 99%

Hyperconjugation

Alabugin

Gomes

Abdo

2018

WIREs Comput Mol Sci

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This review outlines the role of hyperconjugative interactions in the structure and reactivity of organic molecules. After defining the common hyperconjugative patterns, we discuss the main factors controlling the magnitude of hyperconjugative effects, including orbital symmetry, energy gap, electronegativity, and polarizability. The danger of underestimating the contribution of hyperconjugative interactions are illustrated by a number of spectroscopic, conformational, and structural effects. The stereoelectronic nature of hyperconjugation offers useful ways for control of molecular stability and reactivity. New manifestations of hyperconjugative effects continue to be uncovered by theory and experiments. This article is categorized under: Structure and Mechanism > Molecular Structures Software > Molecular Modeling Structure and Mechanism > Reaction Mechanisms and Catalysis

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Section: Factors Controlling Hyperconjugationmentioning

confidence: 99%

Hyperconjugation

Alabugin

Gomes

Abdo

2018

WIREs Comput Mol Sci

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“…It is well established that such donors as CSi, CGe, and CSn bonds are capable of providing significant stabilization to a developing positive charge 131–137. However, the relative ability of many common sigma donors, including the most ubiquitous case of CH versus CC bonds, is still widely debated.…”

Section: Factors Controlling Hyperconjugationmentioning

confidence: 99%

Hyperconjugation

Alabugin

Gilmore

Peterson

2011

WIREs Comput Mol Sci

288

289

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This review outlines the ubiquitous nature of hyperconjugative interactions and their role in the structure and reactivity of organic molecules. After defining the common hyperconjugative patterns, we discuss the main factors controlling the magnitude of hyperconjugative effects, including orbital symmetry, energy gap, electronegativity, and polarizibility. The danger of underestimating the magnitude of hyperconjugative interactions are illustrated by a number of spectroscopic, conformational, and structural effects. Through the use of advanced computational techniques, the true role of hyperconjugative effects, as it pertains to their influence on stereoelectronics, conformational equilibria, and reactivities relative to other electronic effects, continue to be uncovered.

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“…As mentioned above, traditionally, the β-Si effect is attributed to the σπ conjugation involving the interaction of the Si–C α σ donor orbital and acceptor π-orbital of a carbocation centered on C β (Figures A and A). − Thus, the stabilization arising from σπ conjugation from a substituent [M] relative to H can be quantified using the isodesmic reaction in eq . …”

Section: Results and Discussionmentioning

confidence: 99%

“…The β-Si effect is generally attributed to hyperconjugation (also called σπ conjugation) through the interaction between an Si–C α σ orbital and the empty π-orbital of a carbocation centered on C β (Figure A). − Other atoms with an empty orbital, such as boron, can engage in this type of hyperconjugation . This effect has also been evoked in considering hyperconjugation between an Si–C α σ orbital and an empty σ* orbital of a C β –X bond (also called σσ conjugation, Figure B). − It should be noted that hyperconjugation is not the only factor that contributes to the β-Si effect.…”

Section: Introductionmentioning

confidence: 99%

Generality and Strength of Transition Metal β-Effects

2018

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Using computation, we examine the generality and strength of β-effects from transition metal centers on β-elimination. In particular, we find that a β-Pd(II) substituent imparts over twice the stabilization to a carbocation as a Si substituent, representative of the well-known β-silicon effect. We established efficient and practical computational parameters to investigate the σσ conjugation in an experimentally relevant system: N, N-picolinamide vinyl metalacycles with β-substituents that can undergo elimination. We have found that the β-Pd effect depends on the nature of the C substituent (X): This effect is negligible for X = H, Me, OH, and F, but is significant for X = Cl, Br, and I. We have also extended these studies to the β-effect in N, N-picolinamide vinyl metalacycles with β-substituents of other transition metals-Fe(II), Ru(II), Os(II), Co(III), Rh(III), Ir(III), Ni(II), Pd(II), Pt(II), Cu(III), Ag(III), and Au(III). We found that the electronegativity of the metals correlates reasonably well with the relative β-effects, with first-row transition metals exerting the strongest influence. Overall, it is our anticipation that a more profound appreciation of transition metal β-effects will facilitate the design of novel reactions, including new variants of transition metal catalyzed C-H functionalization.

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Stereoelectronic Effects of the Group 4 Metal Substituents in Organic Chemistry

Cited by 20 publications

References 197 publications

Hyperconjugation

Hyperconjugation

Hyperconjugation

Generality and Strength of Transition Metal β-Effects

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