Hydrogenase biomimetics: structural and spectroscopic studies on diphosphine-substituted derivatives of Fe2(CO)6(µ-edt) (edt = ethanedithiolate) and Fe2(CO)6(µ-tdt) (tdt = 1,3-toluenedithiolate)

Abstract

Hydrogenase biomimetics: structural and spectroscopic studies on diphosphine-substituted derivatives of Fe2(CO)6(µ-edt) (edt = ethanedithiolate) and Fe2(CO)6(µ-tdt) (tdt = 1,3-toluenedithiolate).

Synthesis, structures, and electrocatalytic properties of phosphine‐monodentate, −chelate, and ‐bridge diiron 2,2‐dimethylpropanedithiolate complexes related to [FeFe]‐hydrogenases

“…For the diphosphine‐bridge complexes 4a and 4b , their IR spectra display the similar carbonyl absorption patterns in the region of 1997–1904 cm −1 while the 31 P{ 1 H} NMR spectra give only a sharp singlet at δ P 124.5 or 54.5 ppm (Table ), being in well agreement with the observation in the reported diiron bridge complexes Fe 2 ( μ ‐xdt)(CO) 4 { μ ‐(Ph 2 P) 2 X} (X = CH 2 , NR) with pdt, edt, odt, adt NR bridges . It is also seen from Table that the average ν C ≡ O value of the PNP‐bridge complex 4a is bigger than those of the PCP‐bridge analogue 4b , possibly owing to the fact that the weaker electron‐donating abilities of the PNP ligands such as (Ph 2 P) 2 NPh relative to the PCP ligand like dppm lead to the lower back‐donating π‐bonding electron transfer from Fe to CO.…”

“…In the meanwhile, the 31 P{ 1 H} NMR spectra of the monophosphine‐monodentate complexes 1a , 1b , and 2a display only one strong singlet at δ P 62.6, 64.6, and 91.5 ppm for their P atoms attached to one iron core (Table ), respectively. By contrast, two well‐resolved doublets with the 2 J PP value of 78 Hz are observed at δ P 57.9 and − 26.3 ppm for the coordinated and free P atoms in the 31 P{ 1 H} NMR spectrum of the diphosphine‐monodentate complex 2b (Table ), being consistent with the known dppm‐monosubstituted diiron complexes of the type Fe 2 ( μ ‐dithiolate)(CO) 5 ( k 1 ‐dppm) with pdt, edt, odt or adt NR bridges . In addition, the 1 H NMR spectra of 1a , 1b , 2a , and 2b all display two sets of aryl proton signals in the downfield region of δ H 7.8–7.1 ppm for their phenyls of the phosphine ligands and two groups of alkyl proton signals in the upfield region of δ H 2.0–1.1 ppm together with two singlet signals in the more upfield region of δ H 1.0–0.4 ppm for their methenes and methyls of the Me 2 pdt bridges.…”

“…Inspired by these findings mentioned above and in comparison with the previous studies on the substitutions of diiron hexacarbonyl complexes bearing some dithiolate bridges such as pdt, edt and adt NR , little attention has been however paid to the reactions of all‐carbonyl diiron complexes with bulky dithiolate bridges such as Me 2 pdt [(SCH 2 ) 2 CMe 2 ], Et 2 pdt [(SCH 2 ) 2 CEt 2 ], etc . In this work, we carried out the treatments of parent complex Fe 2 ( μ ‐Me 2 pdt)(CO) 6 ( A ) with common monophosphines P(C 6 H 4 R‐ p ) 3 (R = Me, Cl) or small bite‐angle diphosphines (Ph 2 P) 2 X (X = CH 2 (dppm), NPh, NBu n ) in different conditions, mainly aiming to i) observe the potential influence of the diverse coordination modes (monodentate, chelate, bridge) of phosphine ligands in diiron complexes with bulky Me 2 pdt bridge on their formation, structures, and electrocatalytic behaviors, and to ii) further develop the biomimetic chemistry of [FeFe]‐hydrogenases for proton reduction.…”

“…In this context, in order to explore a class of cheap and efficient artificial catalysts for electrocatalytic proton reduction to H 2 , a great number of diiron dithiolate complexes that mimic the diiron subsite of [FeFe]‐hydrogenases were obtained over the decades . Among the preparation of diiron subsite models, the interesting substitutions of all‐carbonyl diiron complexes Fe 2 ( μ ‐xdt)(CO) 6 (xdt = pdt, (SCH 2 ) 2 CH 2 ; edt, (SCH 2 ) 2 ; adt NR , (SCH 2 ) 2 NR) by small bite‐angle diphosphines (Ph 2 P) 2 X (X = CR 2 named PCP and X = NR' labeled PNP in this study) have attracted much attentions since diverse diiron phosphine complexes can be afforded and have also shown different electrocatalytic properties of proton reduction to H 2 …”

Hydrogenase Biomimetics with Redox-Active Ligands: Synthesis, Structure, and Electrocatalytic Studies on [Fe2(CO)4(κ2-dppn)(µ-edt)] (edt = Ethanedithiolate; dppn = 1,8-bis(Diphenylphosphino)Naphthalene)

“…Consequently, over the past 20 years, the synthesis, structural characterization, and redox properties of a diverse range of diiron-dithiolate complexes has been studied [1][2][3][4][5][6][7][10][11][12][13], most focusing on their role as electrocatalysts for proton-reduction [14,15], but also in hydrogen oxidation [16][17][18][19][20][21][22]. Diphosphine complexes, [Fe 2 (CO) 4 (κ 2 -diphosphine)(µ-dithiolate)], containing a chelating diphosphine are of special interest as they contain an unsymmetrical, redox-active, diiron centre and normally protonate rapidly to afford the corresponding hydride-cations, [Fe 2 (CO) 4 (µ-H)(κ 2 -diphosphine)(µ-dithiolate)] + [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Incorporation of redox-active ligands to the diiron center has also recently gained prominence [29][30][31][32][33]…”