A new Pt2II, II complex (1) has been found to display distinct and O2-dependent reactivity with MeOTf. Under N2 a Pt2IV, IV complex (6) was obtained, while under O2, a Pt2IV, IV complex (7) where the central phenyl ring is transformed to a cyclohexyldienyl was obtained, indicating O2 activation by 1. Complex 1 also reacts readily with oxidants such as R-Cl and H2O2 to form species similar to 7. Reverse transformation of complexes such as 7 back to ...