N-donor effects on carboxylate binding in mononuclear iron(II) complexes of a sterically hindered benzoate ligand.
Using the sterically hindered 2,6-dimesitylbenzoate ligand Mes2ArCO2-, a series of mononuclear Fe(II) carboxylate complexes has been obtained with the general formula (Mes2ArCO2)2Fe(base)2 (base = 1-methylimidazole (MeIm), pyridine (Py), 2-picoline (2-Pic), 2,5-lutidine (2,5-Lut), 2,6-lutidine (2,6-Lut), (base)2 = N,N,N',N'-tetramethylethylenediamine (TMEDA)). For the monodentate base adducts, single-crystal X-ray diffraction studies revealed several different structural types ranging from distorted tetrahedral to distorted octahedral that correlate with the degree of alpha-substitution of the N-donors. Increasing alpha-substitution leads to the lengthening of the Fe-N bond, which in turn results in a change in carboxylate binding mode from eta 1 to eta 2. We surmise that this change is due to an electrostatic effect and is driven by increasing the Lewis acidity of the Fe center. Such a simple process for inducing carboxylate shifts could play a critical role in biological systems.
Hagadorn
J R
JR
207 Pleasant St S.E., Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Que
L
L
Tolman
W B
WB
D001565:Benzoates / Q000138:chemical synthesis / Q000737:chemistry*; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D007501:Iron; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure
D001565:Benzoates; D005296:Ferrous Compounds; D008024:Ligands; D007501:Iron