Structure and bonding in monomeric iron(III) complexes with terminal oxo and hydroxo ligands.
We report on the structure and bonding in the title iron(III) complexes, containing the tris[(N'-tert-butylureayl)-N-ethyl]amine ligand, with density functional theory techniques. In agreement with the experimental data, a high-spin electronic state is favored for all of the systems we considered. H bonds between the terminal oxo and hydroxo ligands and NH groups present in the organic ligand coordinated to the metal have a remarkable effect on the overall coordination geometry. In fact, the structure of model complexes without H bonds shows shorter Fe-O bond lengths. This is a consequence of the ability of the H bonds to stabilize a remarkable amount of electron density localized on the terminal oxo and hydroxo ligands. Energy analysis indicates that each H bond stabilizes the nonheme complexes by roughly 35 kJ/mol. Molecular orbital analysis indicates a reduction of two Fe-O bonding electrons on going from a complex with a terminal oxo ligand to a complex with a terminal hydroxo ligand. This reduction in the number of bonding electrons is also supported by frequency analysis.
Dipartimento di Chimica, Università di Salerno, Baronissi (SA), Italy.
Josè Gracia
JG
Budrìa
Simone
S
Raugei
Luigi
L
Cavallo
D005290:Ferric Compounds / Q000737:chemistry*; D006860:Hydrogen Bonding; D006878:Hydroxides / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry*
D005290:Ferric Compounds; D006878:Hydroxides; D008024:Ligands; D010100:Oxygen