Cationic Terminal Borylenes by Halide Abstraction:  Synthesis and Spectroscopic and Structural Characterization of an FeB Double Bond

The synthesis and the spectroscopic and structural characterization of the cationic terminal borylene complex [Cp*Fe(CO)<sub>2</sub>(BMes)]<sup>+</sup> are reported. Halide abstraction from the corresponding bromoboryl species using Na[BAr<i><sup> </sup></i><sup></sup><i><sup>f</sup></i><sup></sup><sub>4</sub>] generates the borylene as the [BAr<i><sup> </sup></i><sup></sup><i><sup>f</sup></i><sup></sup><sub>4</sub>]<sup>-</sup> salt in ca. 50% yield. Analyses of IR, NMR, crystallographic, and DFT data are consistent with the presence of an FeB double bond.