The (metal-metal)-nonbonding[Fe2(CO)6(.mu.2-PPh2)2]2- dianion. Synthesis, structural analysis of its unusual dimeric geometry, and stereochemical-bonding implications

XAFS and DFT Characterisation of Protonated Reduced Fe Hydrogenase Analogues and Their Implications for Electrocatalytic Proton Reduction

“…While the structural details of DP 2-have been determined crystallographically, [21] limited structural information is available from the XAFS of DP-H 2 , and only IR spectra of DP-H 1-can be used to anchor the computational results. For the protonated compounds, different isomeric forms are possible, and the structural parameters, relative computed energies and spectroscopic signatures may be compared with experimental results.…”

“…For comparison, selected bond lengths for the previously reported X-ray structure [21] and optimised geometry for {DP 2-} [10,22] are presented in Table 2. While there is close agreement between the calculated and observed Fe-C and C-O distances and the planar Fe-P-P-Fe core geometry, poor numerical agreement is obtained for the non-bonding Fe-Fe and Fe-P distances, these being overestimated by 0.077 Å and 0.056 Å, respectively, relative to the crystallographic values.…”

“…While there is close agreement between the calculated and observed Fe-C and C-O distances and the planar Fe-P-P-Fe core geometry, poor numerical agreement is obtained for the non-bonding Fe-Fe and Fe-P distances, these being overestimated by 0.077 Å and 0.056 Å, respectively, relative to the crystallographic values. [21] [e] Fe-CO and CO distances for the CO groups on the Fe(CO) 3 fragment.…”

XAFS of short-lived reduction products of structural and functional models of the [Fe–Fe] hydrogenase H-cluster

“…In this case reduction is associated with a flattening of the 2Fe2P core geometry and an increase in the Fe-Fe distance by ca. 1 Å (Ginsburg et al, 1979). Electrochemical generation of the two-electron reduced product was confirmed, in line, by IR spectroscopy and the sample once collected in the XAFS cell was rapidly frozen at 80 K and stored at that temperature prior to data collection.…”

“…The Fe-Fe, Fe-S and Fe-CO distances obtained from the XAFS refinement have been used to build the starting model for a DFT based structure refinement Lyon et al (1999). b From Ginsburg et al (1979). calculation (Gaussian: Frisch et al, 2003).…”