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)₂(BMes)]⁺ are reported. Halide abstraction from the corresponding bromoboryl species using Na[BAr^f₄] generates the borylene as the [BAr^f₄]^- salt in ca. 50% yield. Analyses of IR, NMR, crystallographic, and DFT data are consistent with the presence of an FeB double bond.