Pulse Radiolysis of Metal‐Organic Compounds. I. Aluminiumalkyl‐naphthalene‐diethylether‐system

Abstract

AbstractAn attempt was made to simulate metal‐organic reactions of the triethylaluminium‐naphthalene‐diethylether‐system by pulse radiolysis. Using 1 μs‐pulses a partial absorption spectrum of esol− in ether in the range from 800 to 1200 nm was obtained at room temperature. The radicals and radical‐ions, produced by the pulse radiolysis of argon saturated ether, possess a total absorption spectrum in the range from 210 to 350 nm. The transient absorption decays with mixed order.The intermediates, obtained in argon‐saturated ether solutions of triethylaluminium (10−3 – 10−2 M) have a total absorption spectrum between 220 and 340 nm which changes considerably 50 μs after pulse end. Here too, mixed kinetics are occuring (at 250 nm. k1 ∼ 6 · 104 s−1 and k2/ε ≈︁ 107 cm · s−1). By saturating pure ether with HCl gas the solvated electrons are scavenged. Similar results as in the presence of argon were obtained, showing that the reactivity of H‐atoms is rather high too.A total absorption spectrum of C10H8− and C10H9 species was measured by irradiating naphthalene (10−3 – 10−2 M, argon saturated) in ether. Using again HCl gas as a scavenger for esol− the spectrum of C10H9 radicals was obtained with maxima at 300, 307 and 320 nm. It changes strongly 50 and 100 μs after the pulse, indicating that these species are very reactive, probably with HCl. They disappear in a second order reaction (at 330 nm k2/ε = 2.8 · 106 cm ≈︁ s−1). Subtracting the spectrum of C10H9 from the total one, the absorption spectrum of C10H8− with maxima at 330 and 370 nm was obtained. Its shape does not change very much with time, suggesting that the second order disappearance of the radical‐anions (at 370 nm k2/ε = 5 · 107 cm · s−1) is mainly due to a dimerisation process.Investigating the total absorption spectrum of the complete triethylaluminium‐naphthalene‐diethylether‐system (saturated with argon) at different times after the pulse, the appearance of a new maximum at 312 nm was observed. It was attributed to the intermediate, formed by the reaction of Al(C2H5)2+ and C10H8− and/or C10H9 species. This assumption was supported by analysing the final radiolytic products of the system.A full report of the absorption spectra, kinetic data and product analysis will be published elsewhere.