Organometallic chemistry of platinum-blue derived platinumIII dinuclear complexes

The pivalamidate-bridged Pt-III dinuclear complex [Pt-2((CH3)(3)CCONH)(2)(NH3)(4)(H2O)(2)](4+) (3) reacts with ketones in water to give the ketonyl complexes [Pt-2((CH3)(3)CCONH)(2)(NH3)(4)L](3+), where L is ketonyl and in most cases the alpha-C-H of the ketone is deprotonated. The alpha-C-H activation of the ketone proceeds both by homolytic cleavage and electrophilic displacement of proton by Pt-III. Complex 3 reacts also with olefins in water to give beta-hydroxyalkyl Pt-III dinuclear complexes. In acidic water, these complexes release ketones or epoxides and the Pt-III dinuclear complexes are reduced to the corresponding Pt-III dinuclear complex [Pt-2((CH3)(3)CCONH)(2)(NH3)(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 a-carbon atoms of the beta-hydroxyalkyl Pt-III complexes undergo nucleophilic attack by water, and alpha,beta-dihydroxyalkanes are released. Complex 3 reacts also with alkynes in water to give the ketonylplatinum(III) dinuclear complexes. All of the above reactions show that the Pt-III dinuclear complex has both Pt-II and Pt-IV characters; coordination of olefins is a Pt-II character, whereas nucleophilic attack on the coordinated alpha-carbon atom is a Pt-IV character. The electron delocalization and flexibility along the Pt-Pt bond make these unique characters of the Pt-III, complex possible. (C) 2002 Elsevier Science B.V. All rights reserved.