The partial oxidation of methane to methyl trifluoroacetate (MeTFA) in trifluoroacetic acid (HTFA) is one of the most selective methane conversion reactions. We report that the simple anionic form of palladium, PdCl₄^2- can effectively convert methane to MeTFA compared to neutral PdCl₂ in the K₂S₂O₈-HTFA oxidation system. The anionic catalyst form appears to increase the Pd solubility in the polar protic HTFA solvent, thereby facilitating transformation to PdTFA₄^2- which is supposed to be the real catalytic species in this PdCl₄^2- - catalyzed methane oxidation. It was found that not only methane oxidation but also solvent HTFA oxidation proceeded to a substantial degree, which limited the yield of MeTFA by consuming the oxidant, K₂S₂O₈. Furthermore, for the first time, the role of trifluoroacetic anhydride (TFAA) was identified; it removes water produced by KHSO₄ and HF, which are the reduced form of K₂S₂O₈ and the oxidation byproduct of HTFA, respectively. The reaction equations for methane to MeTFA, and HTFA to CO₂ in K₂S₂O₈-HTFA system are suggested.

甲烷在三氟乙酸 (HTFA) 中部分氧化为三氟乙酸甲酯(MeTFA) 是最具选择性的甲烷转化反应之一。我们报告说，与 K ₂ S ₂ O ₈ -HTFA 氧化系统_{中的中性 PdCl 2}相比，钯的简单阴离子形式 PdCl ₄ ^{2-可以有效地将甲烷转化为 MeTFA。}阴离子催化剂形式似乎增加了 Pd 在极性质子 HTFA 溶剂中的溶解度，从而促进向 PdTFA ₄ ^2-的转化，这被认为是该 PdCl ₄ ^{2-中的真正催化物质}- 催化甲烷氧化。发现不仅甲烷氧化而且溶剂HTFA氧化也进行到相当程度，这通过消耗氧化剂K ₂ S ₂ O ₈限制了MeTFA的收率。此外，首次确定了三氟乙酸酐（TFAA）的作用；它去除了由 KHSO ₄和 HF 产生的水，它们分别是 K ₂ S ₂ O ₈的还原形式和 HTFA 的氧化副产物。提出了K ₂ S ₂ O ₈ -HTFA体系中甲烷生成MeTFA和HTFA生成CO _{2的反应方程式。}