Diferrate [Fe₂(CO)₆(μ‐CO){μ‐P(aryl)₂}]⁻ as Self‐Assembling Iron/Phosphor‐Based Catalyst for the Hydrogen Evolution Reaction in Photocatalytic Proton Reduction—Spectroscopic Insights

Abstract

This work is focused on the identification and investigation of the catalytically relevant key iron species in a photocatalytic proton reduction system described by Beller and co-workers. The system is driven by visible light and consists of the low-cost [Fe (CO) ] as catalyst precursor, electron-poor phosphines P(R) as co-catalysts, and a standard iridium-based photosensitizer dissolved in a mixture of THF, water, and the sacrificial reagent triethylamine. The catalytic reaction system was investigated by operando continuous-flow FTIR spectroscopy coupled with H gas volumetry, as well as by X-ray absorption spectroscopy, NMR spectroscopy, DFT calculations, and cyclic voltammetry. Several iron carbonyl species were identified, all of which emerge throughout the catalytic process. Depending on the applied P(R) , the iron carbonyl species were finally converted into [Fe (CO) (μ-CO){μ-P(R) }] . This involves a P-C cleavage reaction. The requirements of P(R) and the necessary reaction conditions are specified. [Fe (CO) (μ-CO){μ-P(R) }] represents a self-assembling, sulfur-free [FeFe]-hydrogenase active-site mimic and shows good catalytic activity if the substituent R is electron poor. Deactivation mechanisms have also been investigated, for example, the decomposition of the photosensitizer or processes observed in the case of excessive amounts of P(R) . [Fe (CO) (μ-CO){μ-P(R) }] has potential for future applications.

Two-Coordinate Coinage Metal Complexes as Solar Photosensitizers

“…Electrochemical Results: Electrochemical measurements were performed to evaluate the ground state redox potentials and reversibility of the cationic and anionic species of the cMa complexes in a variety of solvents that are suitable for solar fuels. [36][37][38] Table 2. Electrochemical potentials of cMa complexes in CH2Cl2, DMF, THF, and MeCN.…”

Diiron Aminocarbyne Complexes with NCE− Ligands (E = O, S, Se)

“…The {Fe 2 Cp 2 (CO) x } skeleton (x = 2–3) is a versatile scaffold for building organometallic architectures that take advantage of metal–metal cooperativity [ 29 , 30 , 31 , 32 ], and it can be used to explore novel reactivity patterns exploiting an earth-abundant metal element [ 33 , 34 , 35 ].…”

Ionic Carbon Nitrides in Solar Hydrogen Production and Organic Synthesis: Exciting Chemistry and Economic Advantages

“…Earth abundant substitutes, Cu‐ and Fe‐based sensitizers, are already known. Many research groups share the aspiration to create more sustainable versions of photocatalysts, and extensive work is conducted on synthesis and application of earth‐abundant substitutes – copper iron, nickel, vanadium complexes, just to name a few.…”