ESR Investigations of Radical Additions

Alkyl radicals have also been prepared by reaction of alkylbromides with photolytically generated Re(CO)5 (from Re2(CO)io) [17], photolysis of cobalt-alkyl complexes [20], photolysis of AIBN [17, 21, 22] or thermolysis of TEMPO adducts [23]. 

Besides BuCgo, a series of other monoalkyl- and also monoaryl-radical adducts have been similarly investigated [1, 12, 15-17, 20-23]. The observed hyperfine structures are those expected for the corresponding group R. An unusual long- 

Fluorinated alkyl groups (Rp) can be radically attached to Ggp, for example by reaction of mercury-alkyl compounds under irradiation [10, 24] or by reaction with fluorinated alkyl iodides or bromides [25, 26]. Photochemical reaction with (R3Sn)2 or thermal reaction with RjSnH generates the Rp radical from the corresponding iodides or bromides. 

In the phosphoryl fullerenyl radical the unpaired electron is - similar to the alkylfullerenyl radical - delocalized over two six-membered rings adjacent to the C-P bond [10]. The rotation barrier for the radical C5oP(0)(0 Pr)2 was determined to be 4.8 kcal mol Another phosphorus-containing radical fullerenyl adduct, determined via ESR spectroscopy, is PFjjO BujCgQ. It can be obtained by photolytic reaction of Cgo with HPF4 and tert-butylperoxide in tert-butylbenzene [43]. 

A comparison of the temperature behavior of various RCgQ radicals shows that the dimer bond strength depends on the size of the entering radical (Table 6.1). 

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