Mechanistic Insights and Synthetic Explorations of the Photoredox-Catalyzed Activation of Halophosphines.

ABSTRACT: The light-driven activation of halophosphines R₂PX (R = alkyl- or aryl, X = Cl, Br) by an Ir^III-based photocatalyst is described. It is shown that initially formed secondary phosphines R₂PH react readily with the remaining R₂PX in a parent-child reaction to form diphosphines R₂P-PR₂. Aryl-containing diphosphines can be further reduced to secondary phosphines R^Ar₂PH under identical photoredox conditions. Dihalophosphines RPX₂ are also activated by the photoredox protocol, giving rise to unusual 3-, 4-, and 5-membered cyclophosphines. Transient absorption studies show that the excited state of the Ir photocatalyst is reductively quenched by the DIPEA (N,N-di-iso-propylethylamine) electron donor. Electron transfer to R₂PX is however unexpectedly slow and cannot compete with recombination with the oxidized donor DIPEA^•+. As DIPEA is not a perfectly reversible donor, a small proportion of the total Ir^II population escapes recombination, providing the reductant for the observed transformations.

SUBMITTER: Arkhypchuk AI 

PROVIDER: S-EPMC10647117 | biostudies-literature | 2023 Nov

REPOSITORIES: biostudies-literature