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Steric effects

About: Steric effects is a research topic. Over the lifetime, 16112 publications have been published within this topic receiving 319615 citations. The topic is also known as: steric hindrance.


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Journal ArticleDOI
TL;DR: The facile heterolytic cleavage of H2 is readily achieved at room temperature by the cooperative action of the Lewis acidic borane and Lewis basic phosphine, where the steric congestion precludes quenching of the acid and base via adduct formation.
Abstract: The facile heterolytic cleavage of H2 is readily achieved at room temperature by the cooperative action of the Lewis acidic borane and Lewis basic phosphine, where the steric congestion precludes quenching of the acid and base via adduct formation.

694 citations

Journal ArticleDOI
TL;DR: This Account discusses another class of stable cyclic carbenes, namely, cyclic (alkyl)(amino)carbenes (CAACs), and shows that the peculiar electronic and steric properties of CAACs allow for the stabilization of unusual diamagnetic and paramagnetic main group element species.
Abstract: ConspectusCarbenes are compounds that feature a divalent carbon atom with only six electrons in its valence shell. In the singlet state, they possess a lone pair of electrons and a vacant orbital and therefore exhibit Lewis acidic and Lewis basic properties, which explains their very high reactivity. Following the preparation by our group in 1988 of the first representative, a variety of stable carbenes are now available, the most popular being the cyclic diaminocarbenes.In this Account, we discuss another class of stable cyclic carbenes, namely, cyclic (alkyl)(amino)carbenes (CAACs), in which one of the electronegative and π-donor amino substituents of diaminocarbenes is replaced by a σ-donating but not π-donating alkyl group. As a consequence, CAACs are more nucleophilic (σ-donating) but also more electrophilic (π-accepting) than diaminocarbenes. Additionally, the presence of a quaternary carbon in the position α to the carbene center provides steric environments that differentiate CAACs dramatically fr...

665 citations

Journal ArticleDOI
TL;DR: A systematic look at the available data on C-C bond activation in solution provides some answers to questions about the ligated metal center and the possible mechanisms of C- C bondactivation in various reaction systems.
Abstract: What kind of ligated metal center is necessary for insertion into the "hidden" C-C bond? How can one tune the metal center for C-C bond activation by variation of the steric and electronic properties of ligands? What are the possible mechanisms of C-C bond activation in various reaction systems? A systematic look at the available data on C-C bond activation in solution provides some answers to these questions.

659 citations

Journal ArticleDOI
TL;DR: H-H bonding is shown to be distinct from "dihydrogen bonding", a form of hydrogen bonding with a hydridic hydrogen in the role of the base atom.
Abstract: Bond paths linking two bonded hydrogen atoms that bear identical or similar charges are found between the ortho-hydrogen atoms in planar biphenyl, between the hydrogen atoms bonded to the C1–C4 carbon atoms in phenanthrene and other angular polybenzenoids, and between the methyl hydrogen atoms in the cyclobutadiene, tetrahedrane and indacene molecules corseted with tertiary-tetra-butyl groups. It is shown that each such H–H interaction, rather than denoting the presence of “nonbonded steric repulsions”, makes a stabilizing contribution of up to 10 kcal mol−1 to the energy of the molecule in which it occurs. The quantum theory of atoms in molecules—the physics of an open system—demonstrates that while the approach of two bonded hydrogen atoms to a separation less than the sum of their van der Waals radii does result in an increase in the repulsive contributions to their energies, these changes are dominated by an increase in the magnitude of the attractive interaction of the protons with the electron density distribution, and the net result is a stabilizing change in the energy. The surface virial that determines the contribution to the total energy decrease resulting from the formation of the H–H interatomic surface is shown to account for the resulting stability. It is pointed out that H–H interactions must be ubiquitous, their stabilization energies contributing to the sublimation energies of hydrocarbon molecular crystals, as well as solid hydrogen. H–H bonding is shown to be distinct from “dihydrogen bonding”, a form of hydrogen bonding with a hydridic hydrogen in the role of the base atom.

646 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023942
20221,917
2021346
2020292
2019296
2018307