Synthesis, characterization and DFT studies of 1, 1′-Bis(diphenylphosphino)ferrocene substituted diiron complexes: Bioinspired [FeFe] hydrogenase model complexes

Abstract

The reaction of [Fe 2 (CO) 6 (µ-toluene-3, 4-benzenedithiolate)] 1 and bidentate diphosphine, 1, 1 ′bis(diphenylphosphino)ferrocene (dppf) has been studied. New complexes obtained have been characterized by various spectroscopic techniques as bioinspired models of the iron hydrogenase active site. The crystal structure of [Fe 2 (CO) 5 (κ 1-dppfO)(µ-toluene-3, 4-benzenedithiolate)] 4 is reported.

Diiron Complexes [Fe2(CO)5(μ‐pdt/Mebdt)(L)] Containing a Chelating Diphosphine Ligand L=(Oxydi‐2,1‐phenylene)bis(diphenylphosphine): Bioinspired [FeFe] Hydrogenase Model Complexes

“…The 31 P { 1 H} NMR spectrum for complex 1 showed a peak at 63.40 ppm for the phosphorus bound to the iron center and two peaks at ‐16.39 and ‐18.17 ppm for the free phosphorus see ESI† (Figure S2). This indicates the presence of two isomers, apical and basal in the solution,which has been reported previously for bidentate phosphines …”

“…The Fe ‐ P bond distances in the complexes {Fe(2)‐P(1), 2.2582(8) Å for 1 ; Fe(1)‐P(1), 2.2605(13) for 3 Å; Fe(2)‐P(1), 2.2599 Å for 4 } agree well with similar other reported phosphine complexes. [20b, 32] The P=O bond distance of 1.490(5) Å in complex 4 is much less than the reported P=S bond distance of 1.9445(18) Å but slightly greater than the P=O bond distance (1.4803(15) Å) reported for the complex with dppf . Also, the P=O group points away from the iron carbonyl core.…”

“…The 31 P { 1 H} NMR spectrum for complex 2 showed two signals at 63.9 and 27.5 ppm (see ESI†, Figure S3). The signal at 27.5 ppm indicated the presence of oxidized phosphorus (P=O) . The 31 P { 1 H} NMR spectra for complexes 3 and 4 displayed signals at 60.1, 59.3; ‐19.3, ‐18.5 and 60.8, 60.2; 26.8 ppm, respectively (see ESI†, Figures S4 and S5).…”

“…[23] The absorption spectra of complexes 1 , 3 and 4 were recorded in dichloromethane (Figure and Table ). The transitions in the complexes are mainly from the two iron centers to the dithiolate linkers or to the chelating bidentate phosphine ligand …”

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)

“…The 31 P{ 1 H} NMR spectrum at this temperature is extremely complex (consisting of 15 resonances each of which shows at least one coupling) and consequently attempts to monitor the protonation at this temperature were fruitless. One possible partial solution to this problem is to exchange the pdt-bridge for the far more rigid ligand such as ethane-(edt), benzene-(bdt) or toluene (tdt) dithiolate thus simplifing the system and allowing important information to be more easily abstracted [16][17][18][19].…”