title: Reaction of (mu-oxo)diiron(III) core with CO2 in N-methylimidazole: formation of mono(mu-carboxylato)(mu-oxo)diiron(III) complexes with N-methylimidazole as ligands.
abstract: Several iron(III) complexes with N-methylimidazole (N-MeIm) as the ligand have been synthesized by using N-MeIm as the solvent. Under anaerobic conditions, [Fe(N-MeIm)(6)](ClO(4))(3) (1) reacts with stoichiometric amounts of water in N-MeIm to afford the (mu-oxo)diiron(III) complex, [Fe(2)(mu-O)(N-MeIm)(10)](ClO(4))(4) (3). Exposure of a solution of 3 in N-MeIm to stoichiometric and excess CO(2) gives rise to the (mu-oxo)(mu-carboxylato)diiron(III) species [Fe(2)(mu-O)(mu-HCO(2))(N-MeIm)(8)](ClO(4))(3) (4) and the methyl carbonate complex [Fe(2)(mu-O)(mu-CH(3)OCO(2))(N-MeIm)(8)](ClO(4))(3) (5), respectively. Formation of the formato-bridged complex 4 upon fixation of CO(2) by 3 in N-MeIm is unprecedentated. Methyl transfer from N-MeIm to a bicarbonato-bridged (mu-oxo)diiron(III) intermediate appears to give rise to 5. Complex 3 is a good starting material for the synthesis of (mu-oxo)mono(mu-carboxylato)diiron(III) species [Fe(2)(mu-O)(mu-RCO(2))(N-MeIm)(8)](ClO(4))(3) (where R = H (4), CH(3) (6), or C(6)H(5) (7)); addition of the respective carboxylate ligand in stoichiometric amount to a solution of 3 in N-MeIm affords these complexes in high yields. Attempts to add a third bridge to complexes 4, 6, and 7 to form the (mu-oxo)bis(mu-carboxylato)diiron(III) species result in the isolation of the previously known triiron(III) mu-eta(3)-oxo clusters [[Fe(mu-RCO(2))(2)(N-MeIm)](3)O](ClO(4)) (8). The structures of 3, 4, 6, and 7 allow one, for the first time, to inspect the various features of the [Fe(2)(mu-O)(mu-RCO(2))](3+) moiety with no strain from the ligand framework.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz 95064, USA.
authors.forename: Dana S
authors.initials: DS
authors.lastname: Marlin
authors.forename: Marilyn M
authors.initials: MM
authors.lastname: Olmstead
authors.forename: Pradip K
authors.initials: PK
authors.lastname: Mascharak
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D002384:Catalysis; D018360:Crystallography, X-Ray; D058085:Iron Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D008968:Molecular Conformation; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010084:Oxidation-Reduction
chemical_list: D058085:Iron Compounds; D008024:Ligands; D009942:Organometallic Compounds; D002245:Carbon Dioxide