Gas-phase reactions of Fe(benzyne)+ with simple alkyl halides

An an extension of work on M(benzyne){sup +} complexes (M = Fe, Fe{sub 2}, CoFe, Sc), here the authors report the primary and secondary reactions of Fe(benzyne){sup +} with CH{sub 3}F and the small alkyl halides, C{sub n}H{sub 2n+1}X (n = 1-3; X = Cl, Br, I). Reaction mechanisms are postulated based on the product ion structures which are determined by ion-molecule reactions and collision-induced dissociation. In general, The reactions are observed to proceed by an initial C-X or C-C insertion. If {beta}-hydrogens are present on the alkyl moiety, subsequent {beta}-H transfer and elimination of HX is observed. Secondary reactions generally involve dehydrohalogenation and halogen abstraction. One of the most interesting reactions is with CH{sub 3}I. Following C-I insertion, transfer of the CH{sub 3} group to the benzyne ligand results in an Fe(I)(tolyl){sup +} intermediate which competitively eliminates either FeI to generate C{sub 7}H{sub 7{sup +}} or I{sup {sm_bullet}} to generate FeC{sub 7}H{sub 7{sup +}}. Ion-molecule reactions indicate that the C{sub 7}H{sub 7{sup +}} has an o-tolyliron structure. For larger alkyl halides, however, the analogous reactions are not observed due to the availability of {beta}-hydrogens, which undergo facile transfer and elimination of HX as described above. Finally, the thermochemical implications of these results are discussed.