An open-shell Ir(II)/Ir(IV) redox couple outperforms an Ir(I)/Ir(III) pair in olefin isomerization

Open-shell systems based on first-row transition metals and their involvement in various catalytic processes are well explored. By comparison, mononuclear open-shell complexes of precious transition metals remain underdeveloped. This is particularly true for IrII complexes, as there is very limited information available regarding their application in catalysis. Here we show that a family of IrII metalloradicals, featuring a C6H3-2,6-(OP(tBu)2)2 (POCOP) pincer ligand, effectively catalyses olefin isomerization—a key step in alkane metathesis—exhibiting up to 20 times higher activity than their IrI counterparts. Computational studies reveal that the IrII/IrIV redox cycling enables faster kinetics than the traditional IrI/IrIII pathway owing to reduced barriers for the oxidative addition and reductive elimination steps. Thus, this study presents a redox catalyst involving an IrII/IrIV pair, highlighting the capabilites of precious-metal systems that extend beyond traditional redox cycles. These findings emphasize the need for expanding catalytic design principles, especially for platinum-group metals. The chemistry of precious-metal-based open-shell mononuclear complexes remains underdeveloped. Now it has been shown that iridium metalloradicals enable Ir(II)/Ir(IV) redox cycles and catalyse olefin isomerization more efficiently than their more commonly used closed-shell analogues, which typically operate through Ir(I)/Ir(III) or Ir(III)/Ir(V) cycles.