Calix[4]pyrrole for p-block elements: anti-van’t Hoff-Le Bel configuration and ligand-element cooperativity revive the standard oxidation states.

Información del proyecto

pCx4All

Identificador del acuerdo de subvención: 948708

DOI

10.3030/948708

Fecha de la firma de la CE 4 Septiembre 2020

Fecha de inicio 1 Noviembre 2020

Fecha de finalización 31 Octubre 2026

Financiado con arreglo a

• EXCELLENT SCIENCE - European Research Council (ERC)

Coste total

€ 1 499 500,00

Aportación de la UE

€ 1 499 500,00

Coordinado por

RUPRECHT-KARLS-UNIVERSITAET HEIDELBERG
Germany

Periodic Reporting for period 3 - pCx4All (Calix[4]pyrrole for p-block elements: anti-van’t Hoff-Le Bel configuration and ligand-element cooperativity revive the standard oxidation states.)

Período documentado: 2023-11-01 hasta 2025-04-30

Resumen del contexto y de los objetivos generales del proyecto

State-of-the-art strategies for p-block element-based bond activations predominantly rely on the activity of low-valent species (e.g. silylenes). However, during bond activation, those species usually collapse into the deep thermodynamic sinks of their standard oxidation states, precluding any catalytic cycles. The present proposal PCX4ALL develops new concepts that add unique reactivity to the p-block elements Al, Ga, Si, Ge, Sn and P in their stable oxidation states. This is achieved by the generation of planar anti-van’t Hoff/Le Bel configurations, ligand-element cooperativity, and p-block valence isomerism. All those original features are enabled by calix[4]pyrrole – a well-established ligand for transition metals – which has never been used for p-block elements. Challenging bond activations (e.g. N2) and catalytic transformations (e.g. H2O splitting, acceptorless dehydrogenative oxidation of alcohols) are tackled with the most abundant elements of the earth crust (e.g. a square-planar, tetracoordinated silicon(IV) or aluminum(III)). The concepts are supplemented by photo-induced reactivity and extended into the field of dynamic covalent chemistry. An integrated synthetic, spectroscopic and theoretical research approach guides the way from fundamental understanding to the application in catalysis and materials.

Trabajo realizado desde el comienzo del proyecto hasta el final del período abarcado por el informe y los principales resultados hasta la fecha

During the first reporting period of this project, substantial progress has been made along most research directions outlined in the Description of Action, and beyond. Overall, the calix[4]pyrrolato ligand turned out as versatile and effective for the stabilization of unusual structures and for the initiation of new reactivity modes of p-block elements in their normal (group) oxidation states. Beyond the proposed applications towards aluminum, gallium, silicon, germanium, tin and phosphorous as central elements, we could further extend the range towards the heavier congeners indium, arsenic, antimony and bismuth. Additionally, besides the originally proposed substrates for activation, we could develop the conceptualities of element-ligand cooperation toward dioxygen activation or the catalytic application in ammonia borane dehydrocoupling, and we could include elements also in their lower oxidation states (tin(II)/germanium(II)). Moreover, the project beneficially influenced a broader perspective that deals with the deformation of p-block elements in general.

Avances que van más allá del estado de la técnica e impacto potencial esperado (incluida la repercusión socioeconómica y las implicaciones sociales más amplias del proyecto hasta la fecha)

Beyond the state of the art are recent discoveries on all-metal aromaticity, wherein the calix[4]pyrrolato units act as supramolecular entities to stabilize delicate cationic metal rings. Furthermore, we discovered a unique generation and stabilization protocol for acyclic amino carbenes and their transfer onto transition metals. We expect to exploit these new directions more toward a profound understanding of electronic structures and the herby-created novel reactivities. In addition, the supramolecular trapping of cationic clusters is a valuable goal to extend until the end of this project.

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