Intermolecular Oxidative Addition of Aryl Halides to Platinum(II) Alkyl Complexes

Abstract

We report a well-defined example of intermolecular aryl halide oxidative addition (OA) to Pt­(II). Complexes of the type (IMes)­PtMe2(L) and (IMes′)­PtMe­(L) (L = SMe2, pyridine; IMes = N,N-bis­(2,4,6-trimethylphenyl)­imidazol-2-ylidene; IMes′ = cyclometalated IMes) undergo intermolecular OA of phenyl iodide (PhI) at 60 °C, producing toluene via reductive elimination from a proposed Pt­(IV) phenyl species. Isolation of a model Pt­(IV) OA product provides evidence for a Pt­(II)/Pt­(IV) pathway. The OA of PhI is not limited to Pt­(II) IMes complexes; analogous reactions also proceed with phosphine-ligated Pt­(II) dialkyl complexes, demonstrating that this reaction is feasible for a variety of electron-rich Pt­(II) complexes bearing labile ligands.

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

“…In the methyl region of the 1 H NMR spectrum right after adding MeI (1 M) to a solution of Pt II (0.1 M) and NaI (1.5 M) in acetone- d 6 , two weak singlets appear at 2.93 and 3.42 ppm, with intensity ratios of ∼4:1. Both signals are accompanied by platinum satellites with a 195 Pt– 1 H coupling of, respectively, 80 and 78.5 Hz, characteristic of 2 J PtH in Pt IV methyl complexes. ,− Moreover, there are two sets of cross-peaks in the two-dimensional heteronuclear multiple quantum correlation (2D HMQC) ( 1 H– 195 Pt) spectrum (Figure ): platinum satellites of a stronger 1 H NMR signal at 2.93 ppm show cross-peaks with a 195 Pt NMR signal at −4180 ppm, while Pt satellites of a weaker 1 H NMR signal at 3.42 ppm exhibit cross-peaks with a 195 Pt NMR signal at −5000 ppm.…”

“…The signal in the alkyl region exhibits a single pair of platinum satellites, whereas each signal in the olefin region is accompanied by two pairs of platinum satellites with spin–spin couplings ( J PtC ) of 718 and 131 Hz (the upfield signal) and 8.3 and 169 Hz (the downfield signal). The high spin–spin coupling value J PtC of 718 Hz is characteristic of the α-carbon atom of the vinyl ligand bound to the platinum atom by the σ bond ( 1 J PtC ), ,− and the second set of platinum satellites with a spin–spin coupling of 131 Hz results from additional π-binding of the vinyl moiety with the Pt II iodo complex. Hence, the downfield 13 C signal in the olefin region should be assigned to the C β atom of the vinyl ligand.…”

C(sp2)–C(sp2) Reductive Elimination from a Diarylplatinum(II) Complex Induced by a S–S Bond Oxidative Addition at Room Temperature

“…So far, RE reactions have been extensively investigated in platinum complexes for the construction of various bonds. ,− In this regard, much attention has been paid to formation of C­(sp 3 )–C­(sp 3 ) − or C­(sp 2 )–C­(sp 2 ) − bonds from Pt­(IV) complexes which are, generally, thermally or photochemically induced. In contrast, this reaction has been considerably less explored and is less frequent in Pt­(II) chemistry; in fact, diaryl RE reactions from Pt­(II) centers are often endothermic and slow.…”