Franco Federico, Cometto Claudio, Nencini Luca, Barolo Claudia, Sordello Fabrizio, Minero Claudio, Fiedler Jan, Robert Marc, Gobetto Roberto, Nervi Carlo
Department of Chemistry and NIS, University of Turin, Via P. Giuria 7, 10125, Turin, Italy.
Univ. Paris Diderot, Sorbonne Paris Cité, UMR CNRS 7591, Laboratoire Electrochimie Moléculaire, 75205, Paris 13, France.
Chemistry. 2017 Apr 6;23(20):4782-4793. doi: 10.1002/chem.201605546. Epub 2017 Feb 22.
The electrochemical behavior of fac-[Mn(pdbpy)(CO) Br] (pdbpy=4-phenyl-6-(phenyl-2,6-diol)-2,2'-bipyridine) (1) in acetonitrile under Ar, and its catalytic performances for CO reduction with added water, 2,2,2-trifluoroethanol (TFE), and phenol are discussed in detail. Preparative-scale electrolysis experiments, carried out at -1.5 V versus the standard calomel electrode (SCE) in CO -saturated acetonitrile, reveal that the process selectivity is extremely sensitive to the acid strength, producing CO and formate in different faradaic yields. A detailed spectroelectrochemical (IR and UV/Vis) study under Ar and CO atmospheres shows that 1 undergoes fast solvolysis; however, dimer formation in acetonitrile is suppressed, resulting in an atypical reduction mechanism in comparison with other reported Mn catalysts. Spectroscopic evidence of Mn hydride formation supports the existence of different electrocatalytic CO reduction pathways. Furthermore, a comparative investigation performed on the new fac-[Mn(ptbpy)(CO) Br] (ptbpy=4-phenyl-6-(phenyl-3,4,5-triol)-2,2'-bipyridine) catalyst (2), bearing a bipyridyl derivative with OH groups in different positions to those in 1, provides complementary information about the role that the local proton source plays during the electrochemical reduction of CO .
详细讨论了面式-[Mn(pdbpy)(CO)Br]（pdbpy = 4-苯基-6-(苯基-2,6-二醇)-2,2'-联吡啶）(1)在氩气氛围下乙腈中的电化学行为，以及其在添加水、2,2,2-三氟乙醇（TFE）和苯酚时对CO还原的催化性能。在相对于标准甘汞电极（SCE）为-1.5 V的条件下，于CO饱和的乙腈中进行的制备规模电解实验表明，该过程的选择性对酸强度极为敏感，以不同的法拉第产率生成CO和甲酸盐。在氩气和CO气氛下进行的详细光谱电化学（红外和紫外/可见）研究表明，1会发生快速溶剂解；然而，乙腈中二聚体的形成受到抑制，与其他报道的锰催化剂相比，导致了一种非典型的还原机制。氢化锰形成的光谱证据支持了不同电催化CO还原途径的存在。此外，对新型面式-[Mn(ptbpy)(CO)Br]（ptbpy = 4-苯基-6-(苯基-3,4,5-三醇)-2,2'-联吡啶）催化剂(2)进行的对比研究，该催化剂带有一个在不同位置具有羟基的联吡啶衍生物，与1中的羟基位置不同，提供了关于局部质子源在CO电化学还原过程中所起作用补充信息。
