Carbene-induced synthesis of the first borironium cations using the [(η5-C5Me5)Fe(CO)2]− anion as an unlikely leaving group

Abstract

Reaction of N-heterocyclic carbenes with ferroborirene complex [{(η⁵-C₅Me₅)Fe(CO)₂}{BC₂(SiMe₃)₂}] results in heterolytic Fe–B bond cleavage, yielding borironium ions, a new class of boron-containing heterocycles. The reaction rests on the surprising ability of the reactive [(η⁵-C₅Me₅)Fe(CO)₂]⁻ anion to act as a leaving group. The properties of these species were investigated by multinuclear NMR spectroscopy, as well as single-crystal X-ray diffraction.