The Flash Photolysis of Tetraphenyldiphosphine, Triphenylphosphine, and Diphenylphosphine in Alcohols

Abstract

The photochemical reactions of tetraphenyldiphosphine, triphenylphosphine, and diphenylphosphine in alcohol were studied by flash photolysis and product analysis. The primary photochemical process of all three phosphines studied appeared to be the formation of diphenylphosphinyl radicals which subsequently abstract a-H atoms from the solvent alcohol. The relationship between the rate constants of the abstraction and the a-H bond energies of various alcohols was examined.Les reactions photochimiques de la tktraphknyldiphosphine et des di-et triphknylphosphines ont kt6 ttudiks, dans l'alcool, par photolyse "flash" et par analyse des produits. Le processus photochimique prirnaire pour les trois phosphines semble &tre la formation de radicaux diphknylphosphinyles qui arrachent subs6quemment des atomes d'hydrogkne-a de I'alcool utilisk cornrne solvant. Une relation entre les constantes de vitesse d'abstraction et les energies de liaison des hydrogenes-a de divers alcools a etk examink.

Tandem redox mediator/Ni(ii) trihalide complex photocycle for hydrogen evolution from HCl

“…3 ) leads to the observation of TA signals that are ascribed to diphenylphosphinyl radical. 27 The lifetime of the diphenylphosphinyl radical derived from PPh 3 with and without the presence of 2 [TBA] in solution is the same, consistent with no direct reaction between Ni( ii ) complex and diphenylphosphinyl radical (Fig. S19 † ).…”

“…Diphenyl phosphine is initially formed by photochemical cleavage of the P–C bond and H-atom abstraction from solvent. 27 Photochemical cleavage of the P–H bond in HPPh 2 generates an H-atom equivalent and a diphenylphosphinyl radical. 27 The H-atom participates in halogen-atom abstraction with Ni( ii ) resting state 2 to generate a Ni( i ) intermediate while the accompanying diphenylphosphinyl radical participates in C–H abstraction with solvent to regenerate the diphenylphosphine and close the photoredox cycle.…”

“… 24 The photochemical homolysis of P–H bonds of 2° phosphines generates phosphinyl radicals that display sufficient lifetime (∼160 μs) to participate in halogen-atom abstraction from a Ni( ii ) halide complex to furnish a reduced Ni intermediate that participates in an H 2 evolution cycle; the phosphine photoredox mediator is regenerated by HAA from solvent to close the photocycle. 25 – 27 The H 2 -evolution cycle may eventually be closed by thermally promoted protolytic H 2 evolution with HCl. ‡Crystallographic data for 2 [ClPPh 3 ]: C 36 H 30 Cl 4 P 2 Ni, M = 725.05, orthorhombic, Pbca , a = 17.435(4), b = 15.662(3), c = 24.139(9), V = 6591(2), Z = 8, μ = 1.036 mm –1 , T = 100(2) K, R 1 = 0.0527, w R 2 = 0.0720 (based on all reflections), GooF = 1.030, reflections measured = 57 380, unique reflections = 5858, R int = 0.0741.…”

A (Triphenylphosphine)Silver (I) Complex as a New Performance Additive in Free‐Radical Photopolymerization under Air

“…In combination with our ESR results and Wan investigations on tripheynlphosphines, we can clearly observe the formation of diphenylphosphinyl radical species in toluene solution at a 320 nm maximum wavelength. This maximum is slightly shifted to around 330 nm in polar solvent (like methanol) as described by Wan and co‐workers . The primary radical‐forming process during [Ag](PPh 3 ) photolysis is the cleavage of the phosphorus–phenyl bond from PPh 3 to produce both diphenylphosphinyl and phenyl radical species.…”

“…This maximum is slightly shifted to around 330 nm in polar solvent (like methanol) as described by Wan and co‐workers . The primary radical‐forming process during [Ag](PPh 3 ) photolysis is the cleavage of the phosphorus–phenyl bond from PPh 3 to produce both diphenylphosphinyl and phenyl radical species. According to LFP results, the lifetime of diphenylphosphinyl radicals was evaluated at 61 ± 2.4 µs in argon‐saturated solution (Figure C), whereas in O 2 ‐saturated atmosphere, a pseudo first‐order decay was observed with a second‐order rate constant ( k add (•PPh 2 /O 2 )) > 10 9 M −1 s −1 (Figure D).…”