Reductive Cross-Electrophile C(sp2)–C(sp3) Coupling Catalyzed by PtI2: In Situ Structural Determination of the Intermediates by X‑ray Absorption Spectroscopy and Multinuclear NMR

The reductive cross-electrophile coupling, enabling direct binding of carbon electrophiles, has many benefits over conventional cross-coupling methods that require a carbon nucleophile. Despite the promising potential of this versatile synthetic strategy, the limited insight into the mechanism and reasons for cross-selectivity has held back progress in reaction design and development. Since the discovery of cross-electrophile coupling catalysis by first-row transition metals, it has been believed that the high cross-selectivity of a new C­(sp2)–C­(sp3) bond formation comes from a catalytic cycle combining the polar and radical steps of the oxidative addition of aryl­(vinyl) halides and alkyl halides, respectively. Herein, we report novel PtII-catalyzed cross-electrophile coupling by sequential polar oxidative addition of C­(sp2)- and C­(sp3)-electrophiles to selectively form a cross-coupling product. The designed catalytic system turned out to be easy to handle, insensitive to air, and involving no radical steps, allowing in situ characterization of the reaction intermediates by 1H, 13C, and 195Pt NMR as well as X-ray absorption spectroscopy Pt L3-edge techniques and thus shedding light on the reaction mechanism.