Anion-Dependent Switch in C–X Reductive Elimination Diastereoselectivity

Reaction of a complex Pt organometallic species with electrophilic halogen sources in the presence of X^– ligands changes the mechanism of reductive elimination from a concerted reductive coupling type to an S_N2 type reductive elimination. In the absence of the added X^– ligand the reductive elimination is stereoretentive; in its presence, the process is stereoinvertive. This selectivity hinges on the reactivity of a key five-coordinate Pt­(IV) intermediate with the X^– ligand.