Di-Iron Aza Diphosphido Complexes:  Mimics for the Active Site of Fe-Only Hydrogenase, and Effects of Changing the Coordinating Atoms of the Bridging Ligand in [Fe₂{μ-(ECH₂)₂NR}(CO)₆]

Abstract

The bis(phosphido)-bridged complex [Fe(2)(mu-PPhH)(2)(CO)(6)] (1) undergoes double deprotonation to give the phosphorus-centered dianionic derivative [Fe(2)(mu-PPh)(2)(CO)(6)](2)(-) (2) which in turn reacts with the tertiary base RN(CH(2)Cl)(2) to give [Fe(2)[(PPhCH(2))(2)NR](CO)(6)] (3) in moderate yield. Treatment of 3 with HBF(4).Et(2)O affords the N-protonated species [Fe(2)[(PPhCH(2))(2)NHR](CO)(6)] BF(4) (4). The structural changes to the heavy atom skeleton of 3 arising from protonation are slight, the most obvious being a ca. 0.03 Alengthening of the N-C bonds.

A Reversible Proton Relay Process Mediated by Hydrogen‐Bonding Interactions in [FeFe]Hydrogenase Modeling

“…[12] The in-situ FTIR measurements ( Figure 1a and S1 in the Supporting Information) reveal the decay of 1 mH,w hich t distance of 3.130(4) i ss horter than the sum of van der Waals radii( 3.35 ). [16] Rauchfuss [9] and Ta larmin et al [7] have reportedt hat model complexes possessing N-protonation are able to form hydrogen-bond interactions with conjugate bases of acids, whereas this work provides ad ifferent perspecScheme2.The interconversionb etween 1SHNMe 2 Ph (left) and 1 mH (right). tive on how acid interacts with the secondary coordination site.…”

“…[6] It has been suggested from intensive investigations on complex modeling that the azadithiolate unit could serve as as econdary coordinations ite for protona ccepting [7, 8] andr elay [9] to the catalytic Fe center.L ess knowni st he reverser oute, which is proton migration of the Fe-hydride to the aza nitrogen bridgehead. Suggestionso n the nitrogen atom's potentialr ole for facilitation of the transfer have been made.…”

Electrochemical Synthesis of Mono‐ and Disubstituted Diiron Dithiolate Complexes as Models for the Active Site of Iron‐Only Hydrogenases

“…[3][4][5][6][7][8][9][10][11] The First structural models were readily accessed by the substitution of two CO ligands with two CN -ligands in [Fe 2 (S 2 C 3 H 6 )(CO) 6 ] (1). [12][13][14] Several structural aspects of the iron-only hydrogenase active site have been modeled by diiron complexes bearing azadithiolate and related bridges, [15][16][17][18] a 2Fe3S core, [19,20] or chelating ligands. [21][22][23][24][25][26] Mimicking the catalytic activity of the hydrogenases turns out to be far more challenging.…”

Nature of hydrogen interactions with Ni(II) complexes containing cyclic phosphine ligands with pendant nitrogen bases

“…Recent structural studies of Fe-only and Ni-Fe hydrogenase enzymes have demonstrated that complexes of these relatively inexpensive and common metals can display high activities for this reaction (1)(2)(3)(4)(5)(6)(7)(8). This has led to the hope that replacement of platinum in fuel cells for the hydrogen oxidation reaction could be achieved with simple synthetic catalysts based on iron or nickel, and many synthetic dinuclear iron complexes, developed as structural models for the enzyme active site, have been studied to explore their fundamental properties and catalytic potential (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Structural features of the Fe-only hydrogenase catalytic site are depicted in structure 1 of Fig.…”