Developing Efficient Suzuki Cross-Coupling Catalysts by Doping Palladium Clusters with Silver
Developing Efficient Suzuki Cross-Coupling Catalysts by Doping Palladium Clusters with Silver
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DOI：
10.1021/acscatal.1c02083
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发表时间：
2021-08-31
期刊：
影响因子：
12.9
通讯作者：
Khanna, Shiv N.
中科院分区：
文献类型：
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作者：
Sengupta, Turbasu;Bista, Dinesh;Khanna, Shiv N.
结果表明，银原子掺杂钯粉可以为铃木-宫浦交叉偶联反应提供有效的催化剂。我们通过考虑涉及溴苯和苯基硼酸作为试剂的模型反应来证明这种有趣的可能性，其中该反应涉及氧化、金属转移和还原步骤。我们使用梯度校正密度泛函理论检查了传统连接 Pd 催化剂、近二十面体 Pd-13 簇和单银掺杂 Pd12Ag 分散剂的所有三个步骤的反应势垒。据观察，与传统的配位 Pd 催化剂和纯 Pd-13 簇相比，在 Pd12Ag 簇中与 Ag 原子相邻的 Pd 位点上进行的反应显示出明显较低的氧化和还原步骤势垒。详细分析表明 Ag 位点向邻近的 Pd 位点提供电荷。虽然这种捐赠可能会降低氧化步骤的障碍，但还原步骤障碍的降低表明各个位点不仅充当供体，而且还可以充当还原步骤的受体。此外，由于Ag和Pd原子的供体-受体特性不同，观察到氧化还原步骤的势垒高度主要取决于所选的活性位点。计算结果表明，通过改变反应活性位点的原子（Ag 或 Pd），可以降低或增加氧化还原步骤的活化能。这表明双金属簇状 Pd12Ag 的活性位点可用于控制合适化学反应的势垒高度。两个簇的势垒高度的相对趋势也被观察到可以通过概念密度泛函理论来预测。我们小组之前的研究表明，通过将 Pd-n 簇支撑在还原石墨烯上，可以降低它们的反应势垒。因此，我们认为银掺杂的 Pd-n 簇可以提供更好的催化剂。
It is shown that doping of a Pd duster by Ag atoms can provide an efficient catalyst for the Suzuki-Miyaura cross-coupling reactions. We demonstrate this intriguing possibility by considering a model reaction involving bromobenzene and phenylboronic acid as reagents where the reaction involves oxidation, transmetallation, and reduction steps. We have examined the reaction barriers of all three steps for a conventional ligated Pd catalyst, a nearly icosahedral Pd-13 cluster, and a monosilver-doped Pd12Ag duster using gradient-corrected density functional theory. It is observed that the reaction carried out on the Pd sites adjacent to an Ag atom in a Pd12Ag cluster shows substantially lower barriers for the oxidation and reduction steps compared to the conventional ligated Pd catalyst and the pure Pd-13 cluster. A detailed analysis indicates that the Ag site donates charge to the neighboring Pd site. While such a donation may have been expected to reduce the barrier for the oxidative step, the lowering of the barrier for the reduction step indicates that the respective sites not only act as a donor but can also serve as an acceptor for the reduction step. Furthermore, because of the differential donor-acceptor characteristic of the Ag and Pd atoms, it is observed that the barrier heights of the redox steps are primarily dependent on the chosen active site. The calculated results show that by altering the atom (Ag or Pd) at the active site of the reaction, the activation energies of the redox steps can either be reduced or increased. This shows that the active sites of a bimetallic cluster-like Pd12Ag can be utilized to control the barrier heights of suitable chemical reactions. The relative trend of the barrier heights for both clusters is also observed to be predictable by the conceptual density functional theory. Previous studies in our group have indicated that the reaction barriers for Pd-n clusters can be lowered by supporting them on reduced graphene. We, therefore, propose that silver-doped Pd-n clusters may provide an even better catalyst.