Tertiary phosphine disubstituted diiron bis(monothiolate) carbonyls related to the active site of [FeFe]-H2ases: Preparation, protonation and electrochemical properties

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

“…Like most disubstituted diiron dithiolate model compounds, such as Fe 2 (μ-PDT)(CO) 4 (PPhMe 2 ) 2 , 24 Fe 2 [S 2 C 2 (SMe) 2 ](CO) 4 (PPh 3 ) 2 , 64 and Fe 2 [μ-S 2 C 6 H 2 (OH) 2 ](CO) 4 (PPh 3 ) 2 , 25 both the PR 3 ligands in 3- syn and 4- syn have ap/ap coordination configurations, while the two PR 3 ligands in 3- anti and 4- anti have ap/ba coordination configurations, and they are all in contrast with the ba/ba configurations of Fe 2 (μ-PDT)(CO) 4 (PMe 3 ) 2 65 and Fe 2 (μ-PDT)(CO) 4 (PTA) 2 . 23 The Fe(1)–Fe(2) distances of 3- anti (2.5622(10) Å) and 4- anti (2.5751(9) Å) are slightly longer than those of their isomers 3- syn (2.5517(13) Å) and 4- syn (2.5422(14) Å), but they are all longer than those of the sulfur analogues Fe 2 (μ-SBn) 2 (CO) 4 (PMe 3 ) 2 (2.5006(8) Å), 63 Fe 2 (μ-SEt) 2 (CO) 4 (PMe 3 ) 2 (2.5097(7) Å) and Fe 2 (μ-EDT)(CO) 4 (PMe 3 ) 2 (2.5159(6) Å). 18…”

“…These bands are shifted to lower frequencies compared to the 2Fe2S analogues Fe 2 (μ-SBn) 2 (CO) 4 (PPhMe 2 ) 2 (1981–1915 cm −1 ). 63 This could be explained by the fact that Se has a weaker electron-withdrawing ability than S, which leads to an increased back-donation to CO. The 1 H NMR spectra of 3- syn and 4- syn show that only one singlet at 3.27 and 3.67 ppm is assigned to the two methylene groups, which indicates that the two PhCH 2 units are symmetrically arranged.…”

“…(1)-Fe(2) distances of 3-anti (2.5622(10) Å) and 4-anti (2.5751 (9) Å) are slightly longer than those of their isomers 3-syn (2.5517(13) Å) and 4-syn (2.5422(14) Å), but they are all longer than those of the sulfur analogues Fe 2 (μ-SBn) 2 (CO) 4 (PMe 3 ) 2 (2.5006(8) Å), 63 Fe 2 (μ-SEt) 2 (CO) 4 (PMe 3 ) 2 (2.5097(7) Å) and Fe 2 (μ-EDT)(CO) 4 (PMe 3 ) 2 (2.5159(6) Å). 18 Synthesis and characterization of tri-/tetra-substituted diiron carbonyls 5-7…”

“…62 Synthesis and characterization of di-substituted diiron carbonyls Fe 2 (μ-SeCH 2 Ph) 2 (CO) 4 (PR 3 ) 2 (3 and 4) As shown in Scheme 2, different from the above reaction, the PR 3 -disubstituted compound Fe 2 (μ-SeCH 2 Ph) 2 (CO) 4 (PR 3 ) 2 (PR 3 = PPhMe 2 , 3; PMe 3 , 4) could be obtained conveniently and in a high yield as their S analogues by the reaction of Fe 2 (μ-SeCH 2 Ph) 2 (CO) 6 with the PR 3 ligand. 63 The possible reason for this difference may be that the intermediate PR 3 -monosubstituted compound Fe 2 (μ-SePh) 2 (CO) 5 (PR 3 ) is more susceptible to the PR 3 ligand than Fe 2 (μ-SeCH 2 Ph) 2 (CO) 5 (PR 3 ). Interestingly, two independent isomers can be isolated according to different reaction temperatures.…”

Design of Rigidified μ-(9-Fluorenethiolate) {FeFe} Hydrogen Evolving Catalysts

“…The structural changes observed during the first electrochemical step (E) have already been discussed in the previous section. In the following protonation event (chemical step; C) the 1 − species is protonated to form the bridging hydride An equivalent ECEC mechanism is also reported for the monothiolate-bridged complexes Fe 2 (μ-S-CH 2 -Ph) 2 (CO) 4 (PPhMe 2 ) 2 18 and Fe 2 (CO) 5 (μ-naphthalene-2-thiolate) 2 (P(PhOMe-p) 3 ). 16 However, the absence of the terminal bulky phosphine ligand in the latter complex leads to an iron−sulfur bond dissociation during the reduction events so that the complex displays no catalytic activity.…”