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The Radicals cAACMe·AlR2(thf) (R = Me, Et) as Synthons for Aluminum(II)-Centered Radicals AlR2
Kai Oppel1, Julika Hagn1, Ivo Krummenacher1,2
1Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland 97074, Würzburg, Germany.
Abstract:
The iodoalanes cAACMe·AlR2I (cAACMe {= 1-(2,6-di-iso-propylphenyl)-3,3,5,5-tetramethyl-pyrrolidin-2-ylidene}; R = Me, 2Me; Et, 2Et) were prepared and used as precursors for the synthesis of the corresponding aluminyl radicals cAACMe·AlR2(thf) (R = Me, 3Me; Et, 3Et). Characterization by EPR spectroscopy and SC-XRD, as well as DFT calculations revealed 3 to be mainly cyclic (alkyl)(amino)carbene (cAAC)-centered radicals. 3Me and 3Et are rare examples of radicals in the coordination sphere of aluminum and are rare examples of persistent synthons for aluminum(II)-centered radicals. Dissociation of the thf ligand was investigated experimentally, i.e., the exchange of the stabilizing Lewis base and scavenging the radical with organic substrates, and by means of DFT calculations. This dissociation process is a key step in the radical reactivity of 3 and the results reveal the ability of 3 to react as an aluminum-centered radical.
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