Direct functionalization of C−H bonds by electrophilic anions

Abstract

Alkanes and [B12X12]2−(X = Cl, Br) are both stable compounds which are difficult to functionalize. Here we demonstrate the formation of a boron−carbon bond between these substances in a two-step process. Fragmentation of [B12X12]2−in the gas phase generates highly reactive [B12X11]−ions which spontaneously react with alkanes. The reaction mechanism was investigated using tandem mass spectrometry and gas-phase vibrational spectroscopy combined with electronic structure calculations. [B12X11]−reacts by an electrophilic substitution of a proton in an alkane resulting in a B−C bond formation. The product is a dianionic [B12X11CnH2n+1]2−species, to which H+is electrostatically bound. High-flux ion soft landing was performed to codeposit [B12X11]−and complex organic molecules (phthalates) in thin layers on surfaces. Molecular structure analysis of the product films revealed that C−H functionalization by [B12X11]−occurred in the presence of other more reactive functional groups. This observation demonstrates the utility of highly reactive fragment ions for selective bond formation processes and may pave the way for the use of gas-phase ion chemistry for the generation of complex molecular structures in the condensed phase.