Pattanayak Santanu, Siegel Rachel E, Liu Yiming, Fettinger James C, Berben Louise A
Department of Chemistry, University of California Davis CA 95616 USA
Chem Sci. 2025 Feb 13. doi: 10.1039/d4sc07359b.
Primary amines are common functional groups in the reaction environment surrounding an (electro)catalyst, and this includes catalysts ranging from metalloenzymes surrounded by amino acids, to electrocatalysts operating in amine industrial sorbents for CO capture and conversion. This report explores the behavior of amine functional groups at the surface of an electrocatalyst. The possible effects of those amine secondary coordination sphere (SCS) groups on a CO electro-reduction mechanism include stabilization of intermediates and positioning substrate near the active site. Two different clusters were synthesized: [PPN][FeN(CO)(PhPCHCHNH)] (PPN-1) has one amine, and [PPN][FeN(CO)(PhPCHCHNH)] (PPN-2) has two covalently appended amine functional groups (PPN: bis(triphenylphosphine)iminium). Infra-red spectroscopic studies show a direct reaction of each cluster with CO to afford an SCS carbamate functional group, and cyclic voltammetry investigations reveal a variety of roles for the amine SCS groups in the mechanism of catalyst hydride formation and hydride transfer (HT) to CO. The most prominent effect of the amine functional group is stabilization of the intermediate hydride to lower formate yield. With PPN-1, these combined effects serve to shut down HT to CO. With PPN-2, the combined effects result in some loss of selectivity, so that formate and H mixtures (6 : 1) are obtained.
伯胺是（电）催化剂周围反应环境中常见的官能团，这包括从被氨基酸包围的金属酶到在用于CO捕获和转化的胺类工业吸附剂中运行的电催化剂等各种催化剂。本报告探讨了胺官能团在电催化剂表面的行为。这些胺二级配位球（SCS）基团对CO电还原机理的可能影响包括中间体的稳定以及将底物定位在活性位点附近。合成了两种不同的簇合物：[PPN][FeN(CO)(PhPCHCHNH)]（PPN-1）有一个胺基，[PPN][FeN(CO)(PhPCHCHNH)]（PPN-2）有两个共价连接的胺官能团（PPN：双（三苯基膦）亚胺鎓）。红外光谱研究表明，每个簇合物都与CO直接反应生成一个SCS氨基甲酸盐官能团，循环伏安法研究揭示了胺SCS基团在催化剂氢化物形成和氢化物转移（HT）至CO的机理中具有多种作用。胺官能团最显著的作用是稳定中间氢化物以降低甲酸盐产率。对于PPN-1，这些综合作用导致HT至CO的过程停止。对于PPN-2，综合作用导致选择性有所损失，从而得到甲酸盐和H的混合物（6∶1）。
