Rhodium Complexes of 2,6-Bis(dialkylphosphinomethyl)pyridines: Improved C–H Activation, Expanded Reaction Scope, and Catalytic Direct Arylation

The reactivity of (PNP)­Rh­(Ph) (PNP = 2,6-bis­(dialkylphosphinomethyl)­pyridine) toward a variety of electrophiles (Ar–I, ArCH2Cl, O2, I2, B2pin2, and ArSO3H) was explored, and several new modes of oxidative reactivity were observed. Substituting tBu2P for iPr2P provided 100-fold rate enhancement toward C–H bond activation and addressed the previously reported challenge of N2 inhibition. Studying the stoichiometric reactivity of (PNP)Rh complexes toward C–H cleavage and oxidative functionalization led to (PNP)­Rh-catalyzed cross-coupling of aryl iodides with sp2 and sp3 C–H bonds.