Preventing Pd-NHC bond cleavage and switching from nano-scale to molecular catalytic systems: amines and temperature as catalyst activators

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Preventing Pd-NHC bond cleavage and switching from nano-scale to molecular catalytic systems: amines and temperature as catalyst activators

机译：防止Pd-NHC债券乳沟和切换纳米分子催化系统:胺催化剂和温度作为催化剂

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Many reactions catalyzed by Pd complexes with N-heterocyclic carbene (NHC) ligands are performed in the presence of amines which usually act as coupling reagents or mild bases. However, amines can react with Pd/NHC complexes in a number of ways: enhancing molecular catalysis, causing the catalyst deactivation or triggering the ligandless modes of catalysis by producing NHC-free active palladium species. This study gains insight into conditions required for the efficient use of amines as activators of molecular Pd/NHC catalysis and preventing the undesirable reductive cleavage of the Pd-NHC bond in catalytic systems. Reactions of Pd/NHC complexes with various amines within a temperature range of 25140 degrees C and thermal stability of the resulting amino-complexes are examined. The results indicate the major influence of the amine structure and reaction temperature on the catalyst transformation. In particular, thermal decomposition of Pd/NHC complexes with aliphatic amine ligands predominantly leads to reductive Pd-NHC bond cleavage, while deprotonation of the complexes with primary and secondary aliphatic amine ligands in the presence of strong bases at 25-60 degrees C promotes the activation of molecular Pd/NHC catalysis. Efficient Pd-PEPPSI complex-amine systems suitable for strong-base-promoted C-S cross-coupling reactions between aryl halides and thiols are suggested on the basis of these findings.

机译：许多来钯配合物催化反应氮杂卡宾(NHC)配体在胺的存在通常执行作为耦合试剂或轻微的基地。胺能与Pd / NHC复合物的反应多种方式:增强分子催化,导致催化剂失活或触发ligandless模式产生的催化作用NHC-free活跃钯物种。获得洞察所需的条件有效地利用胺为催化剂分子Pd / NHC催化和防止不受欢迎的还原Pd-NHC债券的乳沟在催化系统。复合物中的各种胺25140摄氏度的温度范围内和热所得的amino-complexes的稳定检查。胺的结构和反应的影响温度对催化剂的转换。具体来说,Pd / NHC的热分解与脂肪胺配体复合物主要会导致还原Pd-NHC债券乳沟,而去质子化的复合物初级和二级脂肪胺配体的存在在25-60强大的基地度促进分子的激活Pd / NHC催化。complex-amine系统适用于strong-base-promoted c交叉耦合反应芳基卤化物和硫醇之间的建议这些研究结果的基础。

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《Catalysis science & technology》 |2020年第5期|1228-1247|共20页
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正文语种英语
中图分类汉语教学;
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Activators; catalytic converter; Catalysisaliphatic amineBond cleavagedeprotonationAryl halidesAminesCatalyst deactivation;

机译：催化剂,催化转化器;CatalysisaliphatichalidesAminesCatalyst失活;

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Preventing Pd-NHC bond cleavage and switching from nano-scale to molecular catalytic systems: amines and temperature as catalyst activators

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