Platinum photoredox catalysts for trifluoromethylation

Cyclometalated Pt(II) complexes trifluoromethylate unactivated alkenes in >82% yield under 450 nm LEDs by oxidatively quenching CF3I.

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What reaction do the Pt(II) complexes catalyze?

Visible-light trifluoromethylation of unactivated alkenes and heteroarenes.

What isolated yields were obtained for alkenes?

Greater than 82%; heteroarenes were only moderate.

What catalyst loading and CF3 source were used for alkenes?

1.0 mol% Pt, 1.5 mmol CF3I, DBU, in MeCN.

What light source was used?

Blue LEDs at 450 nm, 7 W, room temperature.

How long for 1-dodecene vs N-methylpyrrole?

6 h and 30 h to completion.

Is light or Pt optional?

No product without the Pt catalyst or photoirradiation.

Which quenching pathway operates?

Oxidative quenching only, because excited-state redox potentials are high.

What happens after ·CF3 adds to the substrate?

A radical that can also propagate with more CF3I; base then eliminates to the product.

What driving force is estimated for regeneration by the substrate radical?

Exceeding 1.43 eV, so sacrificial-donor regeneration is likely limiting.

How do Pt catalysts compare with Ru/Ir standards?

Activities comparable to [Ru(bpy)3]Cl2 and [Ir(ppy)2(dtbbpy)]PF6.

How can back electron transfer be minimized?

Use ligands that are weak π-acceptors or strong σ-donors.