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Cis-Divacant Octahedral Fe(II) in a Dimensionally Reduced Family of 2-(Pyridin-2-yl)pyrrolide Complexes

Journal Article · · Inorganic Chemistry
 [1];  [2];  [2];  [2];  [2]
  1. Texas A & M University, College Station, TX (United States); Texas A&M University
  2. Texas A & M University, College Station, TX (United States)
+ Show Author Affiliations
Four-coordinate transition metal complexes can adopt a diverse array of coordination geometries, with square planar and tetrahedral coordination being the most prevalent. Previously, we reported the synthesis of a trinuclear Fe(II) complex, Fe3TPM2, supported by a three-fold symmetric 2-pyridylpyrrolide ligand (i.e., tris(5-(pyridin-2-yl)-1H-pyrrol-2-yl)methane), that featured a rare cis-divacant octahedral (CDO) geometry at each Fe(II) center. Here, a series of truncated 2-pyridylpyrrolide ligands is described that support mono- and binuclear Fe(II) complexes that also exhibit CDO geometries. Metallation of tetradentate ligand bis(5-(pyridin-2-yl)-1H-pyrrol-2-yl)methane (H2BPM) in THF results in a binuclear complex Fe2(BPM)2(THF)2 in which both Fe(II) ions are octahedrally coordinated. The coordinated THF solvent ligands are labile: THF dissociation leads to Fe2(BPM)2, which features five-coordinate Fe(II) ions. The Fe–Fe distance in these binuclear complexes can be elongated by ligand methylation. Metalation of bis(5-(6-methylpyridin-2-yl)-1H-pyrrol-2-yl)methane (H2BPMMe) in THF leads to the formation of four-coordinate, CDO Fe(II) centers in Fe(BPMMe)2. Further ligand truncation affords bidentate ligands 2-(1H-pyrrol-2-yl)pyridine (PyrPyrrH) and 2-methyl-6-(1H-pyrrol-2-yl)pyridine (PyrMePyrrH). Metalation of these ligands in THF affords six-coordinate complexes Fe(PyrPyrr)2(THF)2 and Fe(PyrMePyrr)2(THF)2. Dissociation of labile solvent ligands provides access to fourcoordinate Fe(II) complexes. Ligand disproportionation at Fe(PyrPyrr)2 results in the formation of Fe(PyrPyrr)3 and Fe(0). Ligand methylation suppresses this disproportionation and enables isolation of Fe(PyrMePyrr)2, which is rigorously CDO. Complete ligand truncation, by separating the 2-pyridylpyrrolide ligands into the constituent monodentate pyridyl and pyrrolide donors, affords Fe(Pyr)2(Pyrr)2 in which the Fe(II) is tetrahedrally coordinated. Computational analysis indicates that the potential energy surface that dictates the coordination geometry in this family of four-coordinate complexes is fairly flat in the vicinity of CDO coordination. Furthermore, these synthetic studies provide the structural basis to explore the implications of CDO geometry on Fe-catalyzed reactions.
Research Organization:
Texas A & M University, College Station, TX (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES); Welch Foundation; National Institutes of Health (NIH)
Grant/Contract Number:
SC0018977
OSTI ID:
2433871
Alternate ID(s):
OSTI ID: 1977869
Journal Information:
Inorganic Chemistry, Journal Name: Inorganic Chemistry Journal Issue: 20 Vol. 60; ISSN 0020-1669
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
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