Organometallic chemistry of platinum-blue derived platinum~Ⅲ dinuclear complexes

摘要

The pivalamidate-bridged Pt~Ⅲ dinuclear complex [Pt_2((CH_3)_3CCONH)_2(NH_3)_4(H_2O)_2]~(4+) (3) reacts with ketones in water to give the ketonyl complexes [Pt_2((CH_3)_3CCONH)_2(NH_3)_4L]~(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~Ⅲ. Complex 3 reacts also with olefins in water to give β-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~Ⅱ dinuclear complex [Pt_2((CH_3)_3CCONH)_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~Ⅲ complexes undergo nucleophilic attack by water, and α,β-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 α-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.