Electro‐ and Photo‐driven Reduction of CO₂ by a trans‐(Cl)‐[Os(diimine)(CO)₂Cl₂] Precursor Catalyst: Influence of the Diimine Substituent and Activation Mode on CO/HCOO⁻ Selectivity

Abstract

A series of [OsII(NN)(CO)2Cl2] complexes where NN is a 2,2′‐bipyridine ligand substituted in the 4,4′ positions by H (C1), CH3 (C2), C(CH3)3 (C3), or C(O)OCH(CH3)2 (C4) has been studied as catalysts for the reduction of CO2. Electrocatalysis shows that the selectivity of the reaction can be switched toward the production of CO or HCOO− with an electron‐donating (C2, C3) or ‐withdrawing (C4) substituent, respectively. The electrocatalytic process is a result of the formation of an Os0‐bonded polymer, which was characterized by electrochemistry, UV/Visible and EPR spectroscopies. Photolysis of the complexes under CO2 in DMF+TEOA produces CO as a major product with a remarkably stable turnover frequency during 14 h of irradiation. Our results suggest that electrocatalysis and photocatalysis occur through two distinct processes, starting mainly from an OsI dimer precatalyst if the reduction is performed by an electrode and an OsI mononuclear species in case of a photoreduction process.

Transition Metal Complexes as Catalysts for the Electroconversion of CO2: An Organometallic Perspective

“…[221] Similar to the ruthenium complexes summarized in Table 5, entry 1a, Castillo et al reported the electropolymerization of the osmium complex at the electrode surface. [219] Moreover,t hey proposed that at low catalyst loadings,t he predominance of monomeric Os I species is responsible for CO generation, while at higher concentrations the formation of dimeric species results in HCO 2 À production. Thel atter occurs in particular after the introduction of electron-withdrawing substituents into the ligand framework.…”

Übergangsmetallkomplexe als Katalysatoren für die elektrische Umwandlung von CO2 – eine metallorganische Perspektive

“…[Ru(tri-R 1 -tpy)L] n+ L = H 2 O, CH 3 CN, CO, di-R 2 -bpy, phen-CO 2 À ,d mphen, [c] Mebimpy, [d] [205] 85 [206] 42 [191] ET M comp. [207] DFT [191,192,[205][206][207][208] 2b [219] 48 [219] n.v.n .v.n .v. 90 [221] 25 [221] ET M exp.…”

“…Ähnlich wie bei den in Tabelle 5, Eintrag 1a, zusammengefassten Rutheniumkomplexen berichteten Castillo et al. über die Elektropolymerisation des Osmiumkomplexes an der Elektrodenoberfläche [219] . Darüber hinaus postulierten sie, dass bei niedrigen Katalysatorbeladungen eine monomere Os I ‐Spezies für die CO‐Erzeugung verantwortlich ist, während bei höheren Konzentrationen die Bildung dimerer Spezies zur Produktion von HCO 2 − führt.…”

“…[221] ¾hnlich wie bei den in Tabelle 5, Eintrag 1a, zusammengefassten Rutheniumkomplexen berichteten Castillo et al über die Elektropolymerisation des Osmiumkomplexes an der Elektrodenoberfläche. [219] ). [159b,c] Bisher waren Cobaltporphyrine (CoP;T abelle 6, Eintrag 3a) Gegenstand beträchtlichen Interesses in mehreren mechanistischen DFT-Studien.…”

A new polypyridyl‐based Ru (II) complex as a highly efficient electrocatalyst for CO2 reduction

“…Consequently, sustainable syngas can result in a greener chemical industry and the production of transported liquid fuels by FT technology. A large number of polypyridyl complexes of transition metals including rhenium, osmium, manganese and ruthenium have been widely used as homogeneous and heterogeneous electrocatalysts for CO 2 reduction to CO. In recent years, synthesis and the electrocatalytic and photocatalytic activity of Dy (III), Gd (III), Re(I), and Ru (II) complexes containing different ligands have been reported for the reduction of CO 2 to CO.…”