Redox Reactions of Amidato‐Bridged cis‐Diammineplatinum(III) Dinuclear Complexes with Phenol

Abstract

Kinetic studies of the redox reactions of the head-to-tail (HT) α-pyridonato-bridged cis-diammineplatinum(III) dinuclear complex and of the head-to-head (HH) α-pyridonato-bridged and α-pyrrolidonato-bridged cis-diammineplatinum(III) dinuclear complexes with phenol were performed in acidic aqueous solution. Reduction of the HH Pt III dinuclear complexes with phenol proceeded only at pH Ͼ 3, whereas that[a] 5571 of the HT Pt III dinuclear complex with phenol proceeded even at a pH as low as zero. The kinetic evaluations revealed that the Pt III dinuclear complexes are not reduced by the phenol molecule but are reduced by the phenoxide ion, and the reduction reaction proceeds through an outer-sphere electron-transfer mechanism.

Axial ligand effect on the reaction mechanism of head-to-head pivalamidato-bridged Pt(III) binuclear complex containing an equatorial bromide ligand with acetone

“…As mentioned in the previous report [10], the rate constants listed in Table 1 are unusually small compared to those for the reactions of the HH amidato-bridged Pt III binuclear complexes with various ligands [6][7][8][9]. Therefore, non-reactivity of the keto form of acetone should also be considered in the present system.…”

“…In step 1, the H 2 O ligated to Pt(Br 2 O 2 ) is substituted with enol acetone to form a p-complex. Subsequently, in step 2, a p-r , Scheme 2 appears to be reasonable, considering the reactivity of the amidato-bridged Pt III binuclear complexes studied so far [6][7][8][9][10][14][15][16][17].…”

“…(8) are listed under the column ''Enol acetone'' in Table 1 and are similar to those for the other systems [6][7][8][9].…”

“…These complexes act as catalysts in the oxidation reactions of olefins to aldehydes, ketones, epoxides, and a,b-diols [2][3][4][5]. In a series of studies on the reaction mechanisms of amidato-bridged Pt III binuclear complexes with organic compounds, we have reported the mechanisms of their reactions with olefins [6,7], phenol [8], isoprene [9], and acetone [10] in acidic aqueous solutions. In our previous report [10], we proposed a mechanism for the reaction of HH tetraammine amidato-bridged platinum(III) binuclear complexes with acetone in strongly acidic aqueous solutions, where acetonylplatinum(III) binuclear complex is formed successively in two steps, as shown in Scheme 1.…”