Novel Ruthenium Phthalocyanine-Containing Model Complex for the Active Site of [FeFe]-Hydrogenases: Synthesis, Structural Characterization, and Catalytic H₂ Evolution

Abstract

The first phthalocyanine (Pc) macrocycle-containing [FeFe]-hydrogenase model complex, (i-BuO)8PcRu­(CO)­(μ-PDT)­[(Ph2P)2NCH2C5H4N]­Fe2(CO)4 (6), has been prepared by a multistep synthetic route. The treatment of 4-picolylamine with Ph2PCl/Et3N in CH2Cl2 at room temperature gave 4-picolyl-substituted azadiphosphine (Ph2P)2NCH2C5H4N (1), whereas further treatment of 1 with diiron complex (μ-PDT)­Fe2(CO)6 in refluxing o-xylene produced the 4-picolylazadiphosphine-chelated diiron complex (μ-PDT)­[(Ph2P)2NCH2C5H4N]­Fe2(CO)4 (2). While 3,6-dihydroxyphthalonitrile reacted with i-BuBr/K2CO3 in DMF at 80 °C to give 3,6-diisobutoxyphthalonitrile 3, further reaction of 3 with lithium wire in refluxing i-BuOH afforded isobutoxyphthalocyanine (i-BuO)8PcH2 (4). Furthermore, 4 reacted with Ru3(CO)12 in refluxing PhCN to give ruthenium phthalocyanine (i-BuO)8PcRu­(CO)2 (5). Finally, CO substitution reaction of 5 with diiron complex 2 in the presence of Me3NO in CH2Cl2 resulted in formation of the targeted model complex 6. While all the new compounds 1–6 were structurally characterized, complex 6 was found to be a catalyst for photoinduced H2 generation.

Investigations on the PNP‐chelated diiron dithiolato complexes Fe2(μ‐edt)(CO)4{κ2‐(Ph2P)2NC6H4R} related to the [FeFe]‐hydrogenase active site

“…While the 31 C NMR spectra of 1 and 2 exhibit triplets at 216.6 and 217.2 ppm for coordinated carbonyls in PFe(CO) 2 units as well as singlets at 212.4 and 212.3 ppm for terminal carbonyls in Fe(CO) 3 groups. In addition, the 31 P NMR spectra of 1 and 2 demonstrate one singlet at 118 ppm ascribe to the apical‐basal isomer and show the other singlet at 105 ppm attributed to the basal‐basal isomer, which is in good agreement with reported analogues Fe 2 (μ‐xdt)(CO) 4 {κ 2 ‐(Ph 2 P) 2 NR} (xdt=pdt, edt, adtNR) [29–34] . As measured by the integration of phosphorus signals in the 31 P NMR spectra, the ratio of apical‐basal versus basal‐basal isomer is 1:0.15.…”

“…In addition, the 31 P NMR spectra of 1 and 2 demonstrate one singlet at 118 ppm ascribe to the apical-basal isomer and show the other singlet at 105 ppm attributed to the basal-basal isomer, which is in good agreement with reported analogues Fe 2 (μxdt)(CO) 4 {k 2 -(Ph 2 P) 2 NR} (xdt = pdt, edt, adtNR). [29][30][31][32][33][34] As measured by the integration of phosphorus signals in the 31 P NMR spectra, the ratio of apical-basal versus basal-basal isomer is 1:0.15.…”

Hydrophilic Quaternary Ammonium‐Group‐Containing [FeFe]‐Hydrogenase Models: Synthesis, Structures, and Electrocatalytic Hydrogen Production

“…Under the guidance of the well‐elucidated H‐cluster structure, synthetic chemists have designed and prepared numerous [FeFe]H 2 ase models; in particular, some of these models have been found to act as catalysts for electrochemical and photoinduced H 2 production in organic solvents, and even in the presence of water . The question is why chemists use water in such catalytic H 2 production, to which the answers are: 1) water may serve not only as a “clean” and cheap solvent, but also as a “clean” and cheap proton source and 2) H 2 production catalyzed by [FeFe]H 2 ases in nature is accomplished in aqueous media at a very low reductive potential (ca.…”

Synthesis of Mono- and Diiron Dithiolene Complexes as Hydrogenase Models by Dithiolene Transfer Reactions, Including the Crystal Structure of [{Ni(S2C2Ph2)}6]

“…[9][10][11][12][13][14] The ready accessibility of this unit also enables the incorporation of additional moieties of interest, for example redox-active components, lightharvesting antennae or water-solubilizing sidechains. [15][16][17][18][19][20][21][22] Although a number of these systems do catalyse the production of H 2 from H + , they generally do so only at a large overpotential, in strongly acid solution (e.g. HClO 4 or CF 3 CO 2 H) and at moderate turnover rates.…”