Tuning the selectivity of P4 reduction at alkaline-earth metal centres

Thum S, Townrow O, Langer J, Harder S (2025)

Publication Type: Journal article

Publication year: 2025

Journal

DOI: 10.1039/d4sc08502g

Abstract

Reduction of P4 with β-diketiminate Mg^I complexes, (BDI)MgMg(BDI), depends strongly on the bulk of the ligand. Whereas superbulky BDI ligands gave selective reduction to P4²⁻ in a butterfly conformation, reduction with a less bulky ligand gave various products among which P8⁴⁻ had a realgar-type structure. The selectivity of P4 reduction can also be controlled by metal choice. Reduction of P4 with Ca^I synthons of general type (BDI*)Ca-X-Ca(BDI*) in which BDI* is a superbulky ligand and X is a bridging dianion (C6H6²⁻ < p-xylene²⁻ < N2²⁻) led to reduction of P4 to the very common, stable Zintl anion P7³⁻. Monitoring this process with ³¹P NMR shows that cyclo-P4²⁻ is an intermediate en route to P7³⁻. Conversion rates increase with increasing reducing power: X = C6H6²⁻ < p-xylene²⁻ < N2²⁻. A complex with the weakly reducing DBA²⁻ dianion led to selective P4 reduction to cyclo-P4²⁻ (DBA = 9,10-dimethyl-diboraanthracene). DBA inhibits P4-to-P7 conversion, most likely by capturing the electron needed for further P4 reduction by radical processes. Experimental investigations are supported by crystal structure determinations and a computational DFT study which also shows that the nature of metal-P4 bonding (covalent or ionic) determines the preference for formation of butterfly-shaped P4²⁻ or planar 6π-electron aromatic cyclo-P4²⁻

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How to cite

APA:

Thum, S., Townrow, O., Langer, J., & Harder, S. (2025). Tuning the selectivity of P4 reduction at alkaline-earth metal centres. Chemical Science. https://doi.org/10.1039/d4sc08502g

MLA:

Thum, Stefan, et al. "Tuning the selectivity of P4 reduction at alkaline-earth metal centres." Chemical Science (2025).

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