SYNERGY OF THEORY AND EXPERIMENT IN THE REMOTE FUNCTIONALIZATION OF ALIPHATIC NITRILES BY BARE FE(I) AND CO(I) CATIONS IN THE GAS-PHASE

The remote functionalization of aliphatic nitriles by the ''bare'' tra nsition-metal ions Fe+ and Co+ has been investigated by means of exten sive quantum chemical calculations and tandem mass spectrometry. The p resent investigation focuses on the chemo- and regioselectivity of bon d activation, using an adequate computational strategy in conjunction with extensive labeling experiments. Nonanitrile, decanitrile, and und ecanitrile have been studied experimentally; both metal ions exhibit a n overall similar reactivity pattern, and molecular hydrogen, methane, and small olefins, respectively, are formed as major neutral fragment s. In the theoretical study, structural and energetic aspects of the n onanitrile/M+ complexes have been investigated in great detail. For bo th Fe+ and Co+, the most favorable pathway of bond activation proceeds via initial C-H bond insertion at C(8), followed by exocyclic activat ion of a C-H bond and reductive elimination of molecular hydrogen via a multicentered transition structure. The calculated barriers lead to predictions with regard to the chemo- and regioselectivity of C-H and C-C bond activation pathways, and these predictions nicely agree with the findings of experiments performed afterward. In contrast to earlie r experimental results, the present calculations reveal no evidence fo r the two metal ions Fe+ and Co+ to activate CH-bonds at different pos itions in the aliphatic chain. The implications of the present investi gations are used to derive a more general mechanistic picture of remot e functionalization in the gas phase.