Thermal C-H borylation using a CO-free iron boryl complex.

New CO-free iron boryl complexes, CpFe(PR3)2(Bpin), are described. The CpFe(PEt3)2(Bpin) derivative is uniquely capable of UV-free arene borylation at 70 °C via a dissociative pathway. Catalytic C-H borylation does not proceed using either monometallic or heterobimetallic schemes, and this failure is rationalized through analysis of relative pKa values for the corresponding iron hydride species.