Tetrachlorocatecholates of triarylarsines as a novel class of Lewis acids

Chishiro, Akane; Akioka, Ippei; Sumida, Akifumi; Oka, Kouki; Tonai, Norimitsu; Yumura, Takashi; Imoto, Hiroaki; Naka, Kensuke

doi:10.1039/d2dt02145e

Cited by 10 publications

(16 citation statements)

References 61 publications

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“…More generally, main group centers can exhibit σ-hole-type Lewis acidity in a variety of ways, such as by altering the coordination number, as discussed above, but also by the geometry, , charge, ,− or, less commonly, by generating open-shell species. One such example is phosphonium cations bearing mono- or bicyclic structures ( XI a,b ) to generate an active pentavalent species ( XI c ) that catalyzes Diels–Alder reactions (Chart ).…”

Section: Altering the σ*−π* Interaction Through Hypervalencymentioning

confidence: 99%

“…However, considering the VSEPR-predicted triagonal bipyramidal geometry (3BP), these molecules surprisingly adopt an unexpected, though not unprecedented, , square pyramidal (4SQ) geometry (Figure ). The geometry enhances the Lewis acidity of the P center, which is now much more sterically accessible for nucleophiles than in the 3BP geometry.…”

Section: Altering the σ*−π* Interaction Through Hypervalencymentioning

confidence: 99%

“…The Lewis acidity arising from the Sb/As−C Ph σ* orbital in these species is enhanced by stabilization of the π-system and/or electronwithdrawing substituents. 5,37,38 While hypervalency is a prominent route to Lewis acidity, a recent study shows that geometrical constrains of trivalent pnictogen centers can also serve as an effective design strategy toward neutral LAs.…”

Section: Lewis Acidity Through λ 5 σ 5 Hypervalencymentioning

confidence: 99%

“…This allows efficient tuning of the Lewis acid strength through reactions with various o-quinones, but the overall electronics can be further tuned with an electron-withdrawing perfluorophenyl group, as in 10b and 11b. 4 However, considering the VSEPR-predicted triagonal bipyramidal geometry (3BP), these molecules surprisingly adopt an unexpected, though not unprecedented, 37,38 square pyramidal (4SQ) geometry (Figure 9). The geometry enhances the Lewis acidity of the P center, which is now much more sterically accessible for nucleophiles than in the 3BP geometry.…”

Section: Altering the σ*−π* Interaction Through Hypervalencymentioning

confidence: 99%

“…For example, neutral λ 5 σ 5 As ( IIX ) and Sb ( IX ) species (Chart ) adopt distorted square pyramidal geometries that project out a σ* orbital to serve as an electron-acceptor site. The Lewis acidity arising from the Sb/As–C Ph σ* orbital in these species is enhanced by stabilization of the π-system and/or electron-withdrawing substituents. ,, While hypervalency is a prominent route to Lewis acidity, a recent study shows that geometrical constrains of trivalent pnictogen centers can also serve as an effective design strategy toward neutral LAs. Recently, trivalent bismuthanes X with a constrained planar geometry around Bi were found to be borderline hard/soft acids.…”

Section: Lewis Acidity Through λ5σ5 Hypervalencymentioning

confidence: 99%

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Unique Phosphorus-Based Avenues for the Tuning of Functional Materials

2023

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Metrics & MoreArticle Recommendations CONSPECTUS: Recent ground-breaking advances in synthetic chemistry have transformed main-group molecules from simple laboratory curiosities into powerful materials for a range of applications in all realms of life. Electron-accepting or -deficient materials, in particular, have been the focus of development since their generally limited availability and stability have been major hurdles in establishing new practical applications. In addition to the general requirements for the design of these materials, a deeper understanding of their inherent electronics and molecular interactions is a requirement for the successful expansion of their utility. Previously, the incorporation of electron-deficient main-group elements, such as boron, into a conjugated organic framework was considered to be an effective route toward the synthesis of high-performing electron-accepting materials. However, challenging conditions such as the need for bulky substituents for kinetic stabilization, air-free and moisture-sensitive synthesis, and restricted storage abilities have led to the investigation of other elements across the periodic table to be used in a similar vein. Lately, heavier main-group elements such as Si, Ge, P, As, Sb, Bi, S, Se, and Te have also proven to be advantageous for electron-accepting materials as they exhibit polarizable molecular orbitals that are easily accessible to electrons or nucleophiles. This has laid the foundation for materials chemistry research on a variety of applications, including optoelectronic devices such as OLEDs, organic photovoltaics, energy storage such as in batteries and capacitors, fluorescent sensors with both biological and physiological applications, organocatalysis and synthesis, and many more. Among the main-group-element-based materials, organophosphorus species are privileged as their frontier orbitals are easily altered by chemical modification or/and structural and geometrical manipulations at the phosphorus center itself, without the need for kinetic stabilization, or through electronic modification of the conjugated system. The five-membered phosphorus-based heterocycle, phosphole, is a particularly interesting motif in this context, and extensive studies on the corresponding materials have uncovered the rich fundamentals of the σ*−π* interaction that imparts intriguing accepting properties while sustaining morphological and physiological stability for utilization in real-life scenarios. Moreover, beyond the σ*−π* interaction in phospholes that is key to many of their acceptor properties as a material, the use of phosphorus also gives rise to easily accessible, low-lying antibonding orbitals. They pave the way for Lewis acid phosphorus species that, despite being considered to be electron-rich species in general, open up several possibilities for intriguing chemical reactivity through hypervalency. Herein, we representatively discuss some recent advancements through the various approaches that leverage the unique structures and electronics...

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Section: Altering the σ*−π* Interaction Through Hypervalencymentioning

confidence: 99%

Section: Altering the σ*−π* Interaction Through Hypervalencymentioning

confidence: 99%

Section: Lewis Acidity Through λ 5 σ 5 Hypervalencymentioning

confidence: 99%

Section: Altering the σ*−π* Interaction Through Hypervalencymentioning

confidence: 99%

Section: Lewis Acidity Through λ5σ5 Hypervalencymentioning

confidence: 99%

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Unique Phosphorus-Based Avenues for the Tuning of Functional Materials

2023

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Exploring the Lewis Acidity and Reactivity of Neutral Pentacoordinate Dithienophospholes

Asok

Zondag

Pradhan

et al. 2023

Chemistry A European J

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A series of luminescent, neutral pentacoordinate dithieno[3,2‐b:2’,3’‐d]phosphole compounds was synthesized by [4+1] cycloaddition of o‐quinones with the corresponding trivalent phospholes. The electronic and geometrical modification of the π‐conjugated scaffold implemented here impacts the aggregation behavior of the species in solution. It proved successful in generating species with improved Lewis acidity of the phosphorus center that was then leveraged for small‐molecule activation. Hydride abstraction from an external substrate involving the hypervalent species is followed by an intriguing P‐mediated umpolung from the hydride to a proton and supports the catalytic potential of this class of main‐group Lewis acids for organic chemistry. This study is a comprehensive investigation into various methods, including electronic, chemical, geometric modifications (and sometimes combinations of these approaches) to systematically improve the Lewis acidity of neutral and stable main‐group Lewis acids with practical value for a range of chemical transformations.

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