Cargando…
Spectroscopic X-ray and Mössbauer Characterization of M(6) and M(5) Iron(Molybdenum)-Carbonyl Carbide Clusters: High Carbide-Iron Covalency Enhances Local Iron Site Electron Density Despite Cluster Oxidation
[Image: see text] The present study employs a suite of spectroscopic techniques to evaluate the electronic and bonding characteristics of the interstitial carbide in a set of iron-carbonyl-carbide clusters, one of which is substituted with a molybdenum atom. The M(6)C and M(5)C clusters are the dian...
Autores principales: | , , , , |
---|---|
Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American
Chemical Society
2019
|
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6784818/ https://www.ncbi.nlm.nih.gov/pubmed/31553598 http://dx.doi.org/10.1021/acs.inorgchem.9b01870 |
_version_ | 1783457812027801600 |
---|---|
author | McGale, Jeremy Cutsail, George E. Joseph, Chris Rose, Michael J. DeBeer, Serena |
author_facet | McGale, Jeremy Cutsail, George E. Joseph, Chris Rose, Michael J. DeBeer, Serena |
author_sort | McGale, Jeremy |
collection | PubMed |
description | [Image: see text] The present study employs a suite of spectroscopic techniques to evaluate the electronic and bonding characteristics of the interstitial carbide in a set of iron-carbonyl-carbide clusters, one of which is substituted with a molybdenum atom. The M(6)C and M(5)C clusters are the dianions (Et(4)N)(2)[Fe(6)(μ(6)-C)(μ(2)-CO)(2)(CO)(14)] (1), [K(benzo-18-crown-6)](2)[Fe(5)(μ(5)-C)(μ(2)-CO)(1)(CO)(13)] (2), and [K(benzo-18-crown-6)](2)[Fe(5)Mo(μ(6)-C)(μ(2)-CO)(2)(CO)(15)] (3). Because 1 and 2 have the same overall cluster charge (2−) but different numbers of iron sites (1: 6 sites → 2: 5 sites), the metal atoms of 2 are formally oxidized compared to those in 1. Despite this, Mössbauer studies indicate that the iron sites in 2 possess significantly greater electron density (lower spectroscopic oxidation state) compared with those in 1. Iron K-edge X-ray absorption and valence-to-core X-ray emission spectroscopy measurements, paired with density functional theory spectral calculations, revealed the presence of significant metal-to-metal and carbide 2p-based character in the filled valence and low-lying unfilled electronic manifolds. In all of the above experiments, the presence of the molybdenum atom in 3 (Fe(5)Mo) results in somewhat unremarkable spectroscopic properties that are essentially a “hybrid” of 1 (Fe(6)) and 2 (Fe(5)). The overall electronic portrait that emerges illustrates that the central inorganic carbide ligand is essential for distributing charge and maximizing electronic communication throughout the cluster. It is evident that the carbide coordination environment is quite flexible and adaptive: it can drastically modify the covalency of individual Fe–C bonds based on local structural changes and redox manipulation of the clusters. In light of these findings, our data and calculations suggest a potential role for the central carbon atom in FeMoco, which likely performs a similar function in order to maintain cluster integrity through multiple redox and ligand binding events. |
format | Online Article Text |
id | pubmed-6784818 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2019 |
publisher | American
Chemical Society |
record_format | MEDLINE/PubMed |
spelling | pubmed-67848182019-10-11 Spectroscopic X-ray and Mössbauer Characterization of M(6) and M(5) Iron(Molybdenum)-Carbonyl Carbide Clusters: High Carbide-Iron Covalency Enhances Local Iron Site Electron Density Despite Cluster Oxidation McGale, Jeremy Cutsail, George E. Joseph, Chris Rose, Michael J. DeBeer, Serena Inorg Chem [Image: see text] The present study employs a suite of spectroscopic techniques to evaluate the electronic and bonding characteristics of the interstitial carbide in a set of iron-carbonyl-carbide clusters, one of which is substituted with a molybdenum atom. The M(6)C and M(5)C clusters are the dianions (Et(4)N)(2)[Fe(6)(μ(6)-C)(μ(2)-CO)(2)(CO)(14)] (1), [K(benzo-18-crown-6)](2)[Fe(5)(μ(5)-C)(μ(2)-CO)(1)(CO)(13)] (2), and [K(benzo-18-crown-6)](2)[Fe(5)Mo(μ(6)-C)(μ(2)-CO)(2)(CO)(15)] (3). Because 1 and 2 have the same overall cluster charge (2−) but different numbers of iron sites (1: 6 sites → 2: 5 sites), the metal atoms of 2 are formally oxidized compared to those in 1. Despite this, Mössbauer studies indicate that the iron sites in 2 possess significantly greater electron density (lower spectroscopic oxidation state) compared with those in 1. Iron K-edge X-ray absorption and valence-to-core X-ray emission spectroscopy measurements, paired with density functional theory spectral calculations, revealed the presence of significant metal-to-metal and carbide 2p-based character in the filled valence and low-lying unfilled electronic manifolds. In all of the above experiments, the presence of the molybdenum atom in 3 (Fe(5)Mo) results in somewhat unremarkable spectroscopic properties that are essentially a “hybrid” of 1 (Fe(6)) and 2 (Fe(5)). The overall electronic portrait that emerges illustrates that the central inorganic carbide ligand is essential for distributing charge and maximizing electronic communication throughout the cluster. It is evident that the carbide coordination environment is quite flexible and adaptive: it can drastically modify the covalency of individual Fe–C bonds based on local structural changes and redox manipulation of the clusters. In light of these findings, our data and calculations suggest a potential role for the central carbon atom in FeMoco, which likely performs a similar function in order to maintain cluster integrity through multiple redox and ligand binding events. American Chemical Society 2019-09-25 2019-10-07 /pmc/articles/PMC6784818/ /pubmed/31553598 http://dx.doi.org/10.1021/acs.inorgchem.9b01870 Text en Copyright © 2019 American Chemical Society This is an open access article published under a Creative Commons Attribution (CC-BY) License (http://pubs.acs.org/page/policy/authorchoice_ccby_termsofuse.html) , which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. |
spellingShingle | McGale, Jeremy Cutsail, George E. Joseph, Chris Rose, Michael J. DeBeer, Serena Spectroscopic X-ray and Mössbauer Characterization of M(6) and M(5) Iron(Molybdenum)-Carbonyl Carbide Clusters: High Carbide-Iron Covalency Enhances Local Iron Site Electron Density Despite Cluster Oxidation |
title | Spectroscopic X-ray and Mössbauer Characterization
of M(6) and M(5) Iron(Molybdenum)-Carbonyl Carbide
Clusters: High Carbide-Iron Covalency Enhances Local Iron Site Electron
Density Despite Cluster Oxidation |
title_full | Spectroscopic X-ray and Mössbauer Characterization
of M(6) and M(5) Iron(Molybdenum)-Carbonyl Carbide
Clusters: High Carbide-Iron Covalency Enhances Local Iron Site Electron
Density Despite Cluster Oxidation |
title_fullStr | Spectroscopic X-ray and Mössbauer Characterization
of M(6) and M(5) Iron(Molybdenum)-Carbonyl Carbide
Clusters: High Carbide-Iron Covalency Enhances Local Iron Site Electron
Density Despite Cluster Oxidation |
title_full_unstemmed | Spectroscopic X-ray and Mössbauer Characterization
of M(6) and M(5) Iron(Molybdenum)-Carbonyl Carbide
Clusters: High Carbide-Iron Covalency Enhances Local Iron Site Electron
Density Despite Cluster Oxidation |
title_short | Spectroscopic X-ray and Mössbauer Characterization
of M(6) and M(5) Iron(Molybdenum)-Carbonyl Carbide
Clusters: High Carbide-Iron Covalency Enhances Local Iron Site Electron
Density Despite Cluster Oxidation |
title_sort | spectroscopic x-ray and mössbauer characterization
of m(6) and m(5) iron(molybdenum)-carbonyl carbide
clusters: high carbide-iron covalency enhances local iron site electron
density despite cluster oxidation |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6784818/ https://www.ncbi.nlm.nih.gov/pubmed/31553598 http://dx.doi.org/10.1021/acs.inorgchem.9b01870 |
work_keys_str_mv | AT mcgalejeremy spectroscopicxrayandmossbauercharacterizationofm6andm5ironmolybdenumcarbonylcarbideclustershighcarbideironcovalencyenhanceslocalironsiteelectrondensitydespiteclusteroxidation AT cutsailgeorgee spectroscopicxrayandmossbauercharacterizationofm6andm5ironmolybdenumcarbonylcarbideclustershighcarbideironcovalencyenhanceslocalironsiteelectrondensitydespiteclusteroxidation AT josephchris spectroscopicxrayandmossbauercharacterizationofm6andm5ironmolybdenumcarbonylcarbideclustershighcarbideironcovalencyenhanceslocalironsiteelectrondensitydespiteclusteroxidation AT rosemichaelj spectroscopicxrayandmossbauercharacterizationofm6andm5ironmolybdenumcarbonylcarbideclustershighcarbideironcovalencyenhanceslocalironsiteelectrondensitydespiteclusteroxidation AT debeerserena spectroscopicxrayandmossbauercharacterizationofm6andm5ironmolybdenumcarbonylcarbideclustershighcarbideironcovalencyenhanceslocalironsiteelectrondensitydespiteclusteroxidation |