The relative rate of CH bond activation by the Pt(II) ion decreased in the order HCH2CH3 > HCH2CH2OH > HCH(OH)CH3. The platinum(II)-ethylene complex, [PtCl3(C2H4)]-1, 1, was the key intermediate in the oxidation of ethane, ethanol, and diethyl ether to 1,2-ethanediol by platinum(II) in aqueous medium. In particular, the intermediary of 1 in the oxidation of ethanol to 1,2-ethanediol and 2-chloroethanol was verified through labelling studies. In D2O, 1, upon oxidation with one of a number of oxidants, converted to [PtCl5(CH2CH2OD)]2-, 2. 2 in turn decomposed to a mixture of 1,2-ethanediol and 2-chloroethanol on heating. The rate conversion of 1 was a function of pH, the anions present, and the oxidant used. While the conversion of 1 to 2 involved a nucleophilic attack by water for hydroxide ion), such a step was not observed in the absence of an oxidant. On basic D2O, the sequential replacement of Cl- by OD- in 1 occurred to successively form [PtCl2(OD)(C2H4)]-, [PtCl(OD)2(C2H4)]- and [Pt(OD)3(C2H4)]-. The process was reversed upon acidification. The species [PtCl5(CH2CHO)]2-, 3, appeared to be the source for the small quantities of hydroxy- and/ or chloroacetaldehyde formed during the oxidation of 1. 3 was synthesized independently by the reaction of acetaldehyde with a mixture of PtCl42-, and PtCl62- in aqueous medium. When 1 was oxidized by Cl2 in CD3OD solution, the principal product was [PtCl5(CH2CO2D)]2- 4, when a small amount of water was present, and CD3OCH2CH2OCD3 in the absence of water.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry
- Materials Chemistry