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

Abstract

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 crosselectrophile coupling catalysis by first-row transition metals, it has been believed that the high cross-selectivity of a new C(sp 2 )−C(sp 3 ) 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 Pt II -catalyzed cross-electrophile coupling by sequential polar oxidative addition of C(sp 2 )-and C(sp 3 )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 1 H, 13 C, and 195 Pt NMR as well as X-ray absorption spectroscopy Pt L 3 -edge techniques and thus shedding light on the reaction mechanism.