Studies focused on the dehydrogenation of amine-borane by diiron complexes that serve as well-characterized rudimentary models of the diiron subsite in [FeFe]-hydrogenase are reported. Complexes of formulation (μ-SCH2XCH2S)[Fe(CO)3]2, with X = CH2, CMe2, CEt2, NMe, NtBu, and NPh, 1-CO through 6-CO, respectively, were determined to be photocatalysts for release of H2 gas from a solution of H3B ← NHMe2 (B:A(s)), dissolved in THF. The thermal displacement of the tertiary amine-borane, H3B ← NEt3 (B:A(t)) from photochemically generated (μ-SCH2XCH2S)[Fe(CO)3][Fe(CO)2(μ-H)(BH2-NEt3)], 1-B:A(t) through 6-B:A(t), by P(OEt)3 was monitored by time-resolved FTIR spectroscopy. Rates and activation barriers for this substitution reaction were consistent with a dissociative mechanism for the alkylated bridgehead species 2-CO through 6-CO, and associative or interchange for 1-CO. DFT calculations supported an intermediate [I] for the dissociative process featuring a coordinatively unsaturated diiron complex stabilized by an agostic interaction between the metal center and the C-H bond of an alkyl group on the central bridgehead atom of the SRS linker. The rate of H2 production from the initially formed 1-B:A(s) through 6-B:A(s) complexes was inversely correlated with the lifetime of the analogous 1-B:A(t) through 6-B:A(t) adducts. Possible mechanisms are presented which feature involvement of the pendent nitrogen base as well as a separate mechanism for the all carbon bridgeheads.
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http://dx.doi.org/10.1021/acs.inorgchem.5b02601 | DOI Listing |
Chem Biol Interact
November 2024
University of Pisa, Department of Chemistry and Industrial Chemistry, Via Giuseppe Moruzzi 13, I-56124, Pisa, Italy. Electronic address:
The new diiron complexes [FeCp(CO)(L)(μ-CO){μ-CN(Me)(Cy)}]CFSO (L = pyridine, 3a; 4-aminopyridine, 3b; 4-dimethylaminopyridine, 3c; 4-trifluoromethylpyridine, 3d; nicotinic acid, 4; Cp = η-CH, Cy = CH = cyclohexyl) were synthesized in moderate to high yields using two distinct synthetic routes from the precursors 1 (L = CO, for 4) and 2 (L = NCMe, for 3a-d), respectively. All products were characterized by IR and multinuclear NMR spectroscopy, and the structures of 3b and 3d were ascertained by X-ray diffraction studies. The behavior of the complexes in aqueous solutions (solubility, Log P, stability) was assessed using NMR and UV-Vis methods.
View Article and Find Full Text PDFJ Am Chem Soc
November 2024
Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.
Carbon monoxide inhibited forms of nitrogenases have carbonyl (CO) and carbide (C) bridges, which are common in synthetic iron complexes with strong-field ligand environments but rare in iron sites with weak-field ligand environments analogous to the enzyme. Here, we explore the fundamental bonding description of bridging CO in high-spin iron systems. We describe the isolation of several diiron carbonyls and related species, and elucidate their electronic structures, magnetic coupling, and characteristic structural and vibrational parameters.
View Article and Find Full Text PDFChembiochem
November 2024
Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, China.
Dalton Trans
November 2024
State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, Dalian University of Technology, Dalian 116024, P. R. China.
Thiolate-bridged bimetallic complexes have attracted considerable attention owing to their extensive applications in bioinspired catalysis as biological metalloenzymes. Compared with bimetallic complexes supported by common thiolate ligands, those featuring functional groups that may adopt different patterns to coordinate to the metal centers are usually difficult to access, limiting their exploration. The benzimidazole moiety is a multi-faceted functional group; for example, it can act as a biomolecule-responsive ligand for the development of transition metal complexes with anticancer and antitumor properties.
View Article and Find Full Text PDFInorg Chem
November 2024
Center for Catalysis and Florida Center for Heterocyclic Chemistry, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States.
Iron hydrides are proposed reactive intermediates for N and CO conversion in industrial and biological processes. Here, we report a reactivity study of a low-coordinate di(μ-hydrido)diiron(II) complex, Fe(μ-H), where is a bis(β-diketiminate) cyclophane, with isocyanides, which have electronic structures related to N and CO. The reaction outcome is influenced by the isocyanide substituent, with 2,6-xylyl isocyanide leading to H loss, to form a bis(μ-1,1-isocyanide)diiron(I) complex, whereas all of the other tested isocyanides insert into the Fe-H bond to give (μ-1,2-iminoformyl) complexes.
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