Electron-transfer reactivity in the activation of organic fluorides by bare metal monocations

In the gas phase, the bare calcium monocation reacts with organic fluorides, via C-F bond activation to yield CaF+ together with the corresponding radical. Ab initio calculations are used to analyse the mechanism of reaction with fluoromethane. Density-functional calculations lead to underestimated reaction barriers, whereas ACPF and CCSD(T) calculations with large basis sets provide good agreement with experiment. The reaction involves a tightly bonded TS in which an electron is transferred from calcium to carbon; this structured harpoon mechanism highlights the simultaneous importance of electron transfer and of metal-fluorine bonding in reductive defluorination processes.