The pivalamidate-bridged Pt I I I dinuclear complex [Pt 2 ((CH 3 ) 3 CCONH) 2 (NH 3 ) 4 (H 2 O) 2 ] 4 + (3) reacts with ketones in water to give the ketonyl complexes [Pt 2 ((CH 3 ) 3 CCONH) 2 (NH 3 ) 4 L] 3 + , where L is ketonyl and in most cases the α-C H of the ketone is deprotonated. The α-C H activation of the ketone proceeds both by homolytic cleavage and electrophilic displacement of proton by Pt I I I . Complex 3 reacts also with olefins in water to give β-hydroxyalkyl Pt I I I dinuclear complexes. In acidic water, these complexes release ketones or epoxides and the Pt I I I dinuclear complexes are reduced to the corresponding Pt I I dinuclear complex [Pt 2 ((CH 3 ) 3 CCONH) 2 (NH 3 ) 4 ] 2 + . When the solution is saturated with O 2 , the olefin oxidation proceeds catalytically. The reaction mechanism is basically similar to the Wacker process. In neutral to basic solution the α-carbon atoms of the β-hydroxyalkyl Pt I I I complexes undergo nucleophilic attack by water, and α,β-dihydroxyalkanes are released. Complex 3 reacts also with alkynes in water to give the ketonylplatinum I I I dinuclear complexes. All of the above reactions show that the Pt I I I dinuclear complex has both Pt I I and Pt I V characters; coordination of olefins is a Pt I I character, whereas nucleophilic attack on the coordinated α-carbon atom is a Pt I V character. The electron delocalization and flexibility along the Pt Pt bond make these unique characters of the Pt I I I complex possible.