Biomimetic hydrogen generation catalyzed by triironnonacarbonyl disulfide cluster

Abstract

O "cluster" dissulfeto de triferrononacarbonila, um precursor sintético e estável para modelos do sítio ativo da enzima hidrogenase [Fe-Fe], foi avaliado como catalisador para a geração eletroquímica de hidrogênio por voltametria cíclica. Na presença de ácido acético, Fe 3 S 2 (CO) 9 catalisa a redução do próton para hidrogênio em -2,24 V (vs. Fc/Fc + ) com um sobrepotencial de -0,78 V (acetonitrila como solvente). O sobrepotencial é comparável àqueles relatados para os modelos diferrocarbonila de hidrogenase [Fe-Fe].Triironnonacarbonyl disulfide cluster, a stable and synthetic precursor for active site models of [Fe-Fe] hydrogenase enzyme, has been evaluated as catalyst for the electrochemical generation of hydrogen by cyclic voltammetry. In the presence of acetic acid, Fe 3 S 2 (CO) 9 catalyzes the reduction of proton to hydrogen at -2.24 V (vs. Fc/Fc + ) with an overpotential of -0.78 V (acetonitrile as solvent). The overpotential is comparable to those reported for diironcarbonyl models of [Fe-Fe] hydrogenase.

Chalcogenide-capped triiron clusters [Fe3(CO)9(μ3-E)2], [Fe3(CO)7(μ3-CO)(μ3-E)(μ-dppm)] and [Fe3(CO)7(μ3-E)2(μ-dppm)] (E = S, Se) as proton-reduction catalysts

“…is not unlike that computed by earlier by Schilling and Hoffmann in related tetrahedral clusters [50] , with the largest concentration of electron density located between the iron centres ligated by the dppm ligand. (irreversible) in MeCN and an irreversible oxidation was also observed at +0.80 V [14] . In [Fe 3 (CO) 9 (µ 3 -CO)(µ 3 -S)] [51] , where both reduction and oxidation (at -0.26 and +0.43 V respectively) are irreversible.…”

“…3 formation via proton-reduction [14][15][16][17][18][19][20][21][22][23][24][25][26][27] . Two groups have independently studied protonreduction by the sulfide cluster [Fe 3 (CO) 9 (µ 3 -S) 2 ] (1S) [14,15] . In MeCN with acetic acid, H 2 production takes place at the second reduction potential (-1.75 V), establishing the dianion [Fe 3 (CO) 9 (µ 3 -S) 2 ] 2-(1S 2-) as the catalyst [14] .…”

“…Two groups have independently studied protonreduction by the sulfide cluster [Fe 3 (CO) 9 (µ 3 -S) 2 ] (1S) [14,15] . In MeCN with acetic acid, H 2 production takes place at the second reduction potential (-1.75 V), establishing the dianion [Fe 3 (CO) 9 (µ 3 -S) 2 ] 2-(1S 2-) as the catalyst [14] . In the presence of the strong acid HBF 4 .Et 2 O, both mono and dianions are active proton-reduction catalysts at potentials of -1.03 V and -1.30 V, respectively [15] .…”

“…Further, the ability to vary the chalcogenide cap potentially allows redoxtuning. Herein we report the electrocatalytic proton-reduction properties of 2 and 3, as well as [Fe 3 (CO) 9 (µ 3 -Se) 2 ] (1Se), the latter being studied in order to compare with previous studies of [Fe 3 (CO) 9 (µ 3 -S) 2 ] (1S) [14,15] .…”

“…With weak acids [Fe 3 (CO) 9 (µ 3 -S) 2 ] (1S) [14] is catalytically active only at the second reduction potential, but with strong acids, it is catalytic at both the first and second reduction potential [15] . We studied the catalytic proton-reduction behaviour of [Fe 3 (CO) 9 (µ 3 -Se) 2 ] (1Se) in both CH 2 Cl 2 ( Figure S6) and MeCN (Figure 8) ) and either H 2 loss (to generate 1Se -) or rapid protonation and H 2 loss to give 1SeH.…”