Biomimics of [FeFe]‑hydrogenases: Diiron aza- versus oxadiphenylpropanedithiolate complexes with mono- versus diphosphines.

To extensively devolep the bioinspired chemistry of [FeFe]‑hydrogenases, this study performs an insigt into the selective substitution of all‑carbonyl diiron aza- versus oxadiphenylpropanedithiolate precursors Fe2(μ-Ph2xdt)(CO)6 (Ph2xdt = Ph2odt = (SCHPh)2O for 1 and Ph2adtNH = (SCHPh)2NH for 2) by mono- versus diphosphines P(C6H4R-p)3 (R = Me and Cl) and (Ph2P)2R' (R' = cis-CH=CH- for dppv and -CH2CH2- for dppe). With monophosphines, their monosubstituted diiron Ph2odt complexes Fe2(μ-Ph2odt)(CO)5){κ1-P(C6H4R-p)3} (R = Me for 1a and Cl for 1b) were obtained through the oxidative decarbonylating of 1 at room temperature in MeCN with Me3NO·2H2O; in contrast, analogous diiron Ph2adtNH complexes Fe2(μ-Ph2adtNH)(CO)5){κ1-P(C6H4R-p)3} (R = Me for 2a and Cl for 2b) were afforded via the photolytic decarbonlating of 2 under UV irradiation (365 nm) in toluene. With diphosphines, the dppv-chelated diiron Ph2xdt complexes Fe2(μ-Ph2xdt)(CO)4(κ2-dppv) (Ph2xdt = Ph2odt for 1c and Ph2adtNH for 2c) were prepared from the UV-irradiated decarbonylation of 1 or 2 in toluene; by contrast, the dppe-chelated diiron similar complexes Fe2(μ-Ph2xdt)(CO)4(κ2-dppe) (Ph2xdt = Ph2odt for 1d and Ph2adtNH for 2d) were synthesized from the Me3NO-assisted decarbonylation of 1 in room-temperature MeCN and that of 2 at refluxing toluene, respectively. The elemental analysis, FT-IR and NMR (1H, 31P) spectroscopy are used for the full elucidation of the molecular structures of these new diiron complexes and X-ray crystallography is applied for further confirmation of 1, 2 and 1a, 2b. The electrochemical properties of representative complexes 1, 1a, 1c and 2, 2a, 2c have been explored and compared with and without acetic acid (AcOH).