A Highly Reactive Rhodium(I)-Boryl Complex as a Useful Tool for C-H Bond Activation and Catalytic C-F Bond Borylation

摘要

Transition-metal-boryl complexes are key intermediates in catalytic hydroboration and borylation reactions and find applications in boron-based materials. Rhodium complexes can be applied in the rhodium-mediated hydroboration or dehydrogenative borylation reactions of olefins or even in the borylation of alkanes. Rhodium and iridium boronates also play a crucial role in the borylation of arenes to give, for instance, Bpin derivatives. Thus, it has been reported that rhodium complexes with boryl and phosphine ligands are intermediates in the catalytic borylation reactions of benzene, toluene, para-xylene, and mesitylene with HBpin (HBpin = 4,4,5,5-tetramethyl-1,3,2-dioxaborolane, pinacolborane). Although it is conceivable that the C—H activation step occurs at the 14-electron species {Rh(Bpin)(PiPr3)2}, density functional theory (DFT) calculations indicate that benzylic activation takes place at {Rh(H)(PiPr3)2}.