Characterization of a paramagnetic, mononuclear Pt(III)-alkyl complex intermediate in carbon-halogen bond coupling reactions.

Addition of Br(2) or I(2) to 14-electron, cationic Pt(II)-alkyl complexes led to the formation of the corresponding carbon-halogen Pt(II) coupling products. Low temperature experiments with Br(2) allowed us to isolate and characterize crystallographically a very unusual mononuclear, paramagnetic Pt(III)-alkyl intermediate with a seesaw structure that can be further oxidized to a transient Pt(IV) species before reductive carbon-halogen coupling reaction takes place.