Phosphinite-Iminopyridine Iron Catalysts for Chemoselective Alkene Hydrosilylation

A series
of new pincer iron complexes with electron-donating phosphinite-iminopyridine
(PNN) ligands has been prepared and characterized. These iron compounds
are efficient and selective catalysts for the anti-Markovnikov alkene
hydrosilylation of primary, secondary, and tertiary silanes. More
importantly, the system exhibits unprecedented functional group tolerance
with reactive groups such as ketones, esters, and amides. Furthermore,
the iron-catalyzed alkene hydrosilylation was successfully applied
to the synthesis of a valuable insecticide, silafluofen. The electronic
properties and structures of the iron complexes have been studied
by spectroscopies and computational methods. Overall, the iron catalysts
may provide a low-cost and environmentally benign alternative to currently
employed precious metal systems for alkene hydrosilylation.