C−H Bond Activation by Dicationic Platinum(II) Complexes

Double protonolysis of diimine platinum dimethyls [(N-N)PtMe_2] (N-N ═ ArNC(Me)C(Me) ═ NAr) generates dicationic Pt(II) complexes that can activate a variety of C−H bonds, liberating 1 equiv of acid and forming organoplatinum species that are moderately stable to the resulting acidic conditions. Ethylbenzenes lead to η^3-benzyl complexes; mechanistic experiments suggest that η^3-benzyl product formation proceeds via C−H bond activation at the benzylic methylene position. In some cases π-arene complexes can be observed, but their role in the C−H activation process is not clear. Cyclohexane and 1-pentene react to give η^3-allyl complexes; allylbenzene gives a chelated phenyl-η^2-olefin structure, as determined by X-ray diffraction. No stable C−H activation products are obtained from methylbenzenes, benzene itself, or alkanes.