Probing Dynamic Equilibria between Platinum(II)−η ² -Benzene Adducts and Unobserved Five-Coordinate Platinum(IV) C−H Oxidative Addition Intermediates

Low-temperature addition of nitrile ligands to platinum(II) η 2 -benzene reagents, [(κ 2 -HTp‘)Pt(η 2 -C 6 H 6 )(R)][BAr‘ 4 ] (R = H, Ph), results in reversible trapping of the postulated five-coordinate C−H oxidative addition product to give cationic platinum(IV) nitrile adducts, [(κ 2 -HTp‘)Pt(C 6 H 5 )(H)(R)(NCR‘)][BAr‘ 4 ] (R = Ph, H, R‘ = Me, CMe 3, p -XC 6 H 4 ). At higher temperatures, irreversible loss of benzene from the Pt(II) η 2 -benzene reagents occurs to form cationic Pt(II) nitrile products.