Pd-Catalyzed arylcyanation reactions are widely applied in academic and industrial problems. We demonstrate for the first time that water acts as a powerful trigger for heterogeneous catalysis in arylcyanation reactions. A selection of trans-Pd(OAc)₂(HNR₂)₂ precatalysts have been synthesized, characterized and kinetically scrutinized as precatalysts for the Pd-catalyzed arylcyanation of aryl bromides. Kinetic and mechanistic studies using in operando infrared spectroscopic analysis reveal the key role played by water, specifically deriving from K₄[Fe(CN)₆]·3H₂O, in facilitating a remarkable switch in mechanism from a homogeneous to heterogeneous catalytic manifold. Evidence for heterogeneity includes sigmoidal kinetic traces, an order in Pd of 0.26 and catalyst turnover sequestration upon addition of excess Hg. The TOF and TON values recorded using K₄[Fe(CN)₆] (<220 ppm H₂O) were higher than when using K₄[Fe(CN)₆]·3H₂O (>4000 ppm H₂O). Catalytic cycles are configured according to the experimental evidence gained from this study. We conclude that water plays a critical role in Pd catalyst speciation in arylcyanation chemistry.

中文翻译：

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在芳基氰化反应中，水在控制Pd催化剂的形成中起着关键作用†

钯催化的芳基氰化反应被广泛应用于学术和工业问题。我们首次证明了水是芳基氰化反应中非均相催化的有力触发因素。已合成，表征和动力学考察了反式-Pd（OAc）₂（HNR ₂）₂预催化剂的选择，这些预催化剂被用作Pd催化的芳基溴化物芳基氰化的预催化剂。在操作红外光谱分析中进行的动力学和力学研究揭示了水所起的关键作用，特别是由K ₄ [Fe（CN）₆ ]·3H ₂衍生而来O，促进机理从均相催化歧管到非均相催化歧管的显着转变。非均质性的证据包括S形动力学轨迹，Pd的阶数为0.26以及在添加过量的Hg时催化剂的转换量保持不变。使用K ₄ [Fe（CN）₆ ]（<220 ppm H ₂ O）记录的TOF和TON值高于使用K ₄ [Fe（CN）₆ ]·3H ₂ O（> 4000 ppm H ₂ O）记录的TOF和TON值。。根据从这项研究中获得的实验证据来配置催化循环。我们得出的结论是，水在芳基氰化化学中的Pd催化剂形态中起着至关重要的作用。