Influence of bidentate phosphine ligands on the chemistry of [FeFe]‐hydrogenase model: insight into molecular structures and electrochemical characteristics

Abstract

SeCH 2 CH(Me)CH 2 Se-μ)(CO) 6 ] (A), by 1,1 0-bis (diphenylphosphino)ferrocene (dppf), 1,2-bis (diphenylphosphino)benzene (dppbz) or 1,2-bis (diphenylphosphino)acetylene (dppac) is investigated. It is found that the reaction product depends on the diphosphine used. In the case of dppf, the product is an intramolecular bridged disubstituted complex [Fe 2 {μ-SeCH 2 CH(Me) CH 2 Se-μ}(CO) 4 {μ,κ 1 ,κ 1 (P,P)-dppf}] (1), while the dppac-reaction produces an intermolecular bridged tetra-iron model [Fe 2 {μ-SeCH 2 CH(Me)CH 2 Se-μ} (CO) 5 ] 2 {μ,κ 1 ,κ 1 (P,P)-dppac} (2). However, the dppbz-reaction gives [Fe 2 {μ-SeCH 2 CH(Me)CH 2 Se-μ}(CO) 4 {κ 2 (P,P)-dppbz}] (3) in which the dppbz ligand is bonded to one Fe atom in a chelated manner. The newly prepared complexes (1-3) have been characterized by elemental analysis, IR, 1 H-, 13 C{H}-, 31 P{H}-, 77 Se{H}-NMR spectroscopy and X-ray structure determination. The electrochemical behavior of 2 and 3, in absence and presence of acid, is described by cyclic voltammetric measurements in CH 2 Cl 2 .

Synthesis, characterization and electrochemical properties of aminophosphine monodentate, ‐chelate, and ‐bridge diiron bis(monothiolate) carbonyls

“…According to the above‐mentioned electrochemical observations and the previously reported similar cases, [25,31,36–41] the ECCE (E=electrochemical, C=chemical) catalytic mechanisms can be speculated for the electrocatalytic H 2 production of 3 in the presence of the weak acid. As shown in Scheme 2, 3 cannot be protonated directly by HOAc.…”

Di-, tri- and tetraphosphine-substituted Fe/Se carbonyls: synthesis, characterization and electrochemical properties

“…In comparison with the phosphine-substituted Fe/Se carbonyls reported in the literature, the E pc1 of compound 4 (−2.14 V) occurs at more negative potential than those of the monophosphine-substituted models Fe 2 {μ-(SeCH 2 ) 2 CHMe}(CO) 5 PPh 3 (−1.97 V), Fe 2 {μ-(SeCH 2 ) 2 CHMe} (CO) 5 P(OMe) 3 (−2.01 V), 73 Fe 2 (μ-Se 2 C 3 H 5 CH 3 )(CO) 5 (PPh 3 ) (−2.0 V), 40 Fe 2 {(μ-SeCH 2 ) 2 O} (CO) 5 (Ph 2 PNMe 2 ) (−1.79 V) and Fe 2 {(μ-SeCH 2 ) 2 O}(CO) 5 {Ph 2 PP(O)Ph 2 } (−1.67 V), 74 but is slightly positive relative to the dppbz substituted model Fe 2 {μ-SeCH 2 CH(Me)CH 2 Se-μ}(CO) 4 (dppbz) (−2.24 V) (dppbz = 1,2-bis(diphenylphosphino)benzene). 75 Furthermore, it is noteworthy that the E pc1 of compound 4 presents a slightly positive potential than those of phosphine disubstituted PDT-bridged diiron compounds Fe 2 (μ-PDT)(CO) 4 (PMe 2 Ph) 2 (−2.22 V) and Fe 2 (μ-PDT)(CO) 4 (PMe 3 )(Ph 2 PCH 2 Py) (−2.20 V). 76 However, as compared to phosphine disubstituted ODT- and ADT-bridged diiron compounds Fe 2 (μ-ADT Ph )(CO) 4 (PMe 3 ) 2 (−2.15 V), Fe 2 (μ-ADT Ph–Br-4 )(CO) 4 (PMe 3 ) 2 (−2.10 V), 77 and Fe 2( μ-ODT)(CO) 4 (PPh 3 ) 2 (−2.02 V), 78 the E pc1 of compound 4 shows a slightly negative potential.…”

“…In comparison with the phosphine-substituted Fe/Se carbonyls reported in the literature, the E pc1 of compound 4 (−2.14 V) occurs at more negative potential than those of the monophosphine-substituted models Fe 2 {μ-(SeCH 2 ) 2 CHMe}(CO) 5 PPh 3 (−1.97 V), Fe 2 {μ-(SeCH 2 ) 2 CHMe} (CO) 5 P(OMe) 3 (−2.01 V), 73 Fe 2 (μ-Se 2 C 3 H 5 CH 3 ) (CO) 5 (PPh 3 ) (−2.0 V), 40 Fe 2 {(μ-SeCH 2 ) 2 O} (CO) 5 (Ph 2 PNMe 2 ) (−1.79 V) and Fe 2 {(μ-SeCH 2 ) 2 O}(CO) 5 {Ph 2 PP(vO)Ph 2 } (−1.67 V), 74 but is slightly positive relative to the dppbz substituted model Fe 2 {μ-SeCH 2 CH(Me)CH 2 Se-μ}(CO) 4 (dppbz) (−2.24 V) (dppbz = 1,2-bis (diphenylphosphino)benzene). 75 Furthermore, it is noteworthy that…”

Synthesis and Electrochemical Investigations of the [FeFe]‐Hydrogenase H‐Cluster Mimics Mediated by Bicyclic Dithiols Derivative

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] It is noteworthy that the nature of the bridging dithiolate linkers has a significant effect on the chemical reversibility as well as the number of electrons implicated in the reduction process. [28][29][30] Among such models, the hexacarbonyl complexes having 1,2-benzenedithiolato bridge, naphthalene-1,8-dithiolato bridge or perylene monoimide of peri-substituted dithiolato bridge showed an enhancement to the stability of their reduced species. [14,23-24,31À 34] This can be explained in terms of the delocalization of electrons over the phenyl ring and hence provides a more energetically favorable proton reduction catalyst.…”