Iron tricarbonyl α-diimine complexes: Synthesis, characterization, and electronic structure based on X-ray crystal structures

A series of iron tricarbonyl α-diimine complexes, Fe(ArDABMe)(CO)3, were synthesized, in which the identity aryl substituent on ligand was varied (ArDABMe = Ar-NC(Me)-(Me)CNAr; 2a Ar C6H5; 2b 3,5-(CH3)2C6H3; 2c 2,4,6-(CH3)3C6H2; 2d 3,5-Cl2C6H3), and complexes characterized by 1H 13C NMR spectroscopy. The IR spectra compounds 2a-d exhibit three carbonyl stretches between 2040 1950 cm−1, all four can be reduced two electrons at potentials −1.8 −2.8 V vs. Cp2Fe/Cp2Fe+. differences νCO reduction are related to electron donating abilities substituents. structures determined single crystal X-ray diffraction experiments; 2a, b, d have distorted square pyramidal structures, whereas, compound is trigonal bipyramidal. In order assess oxidation state 2a-d, we synthesized crystallographically a that contain neutral forms ligands. average CN bond lengths 1.332(1) Å backbone CC 1.403(2) Å, compared 1.279(1) 1.520(3) respectively, lengthening bonds shortening indicative Therefore, best described as containing Fe(I) centers bonded radical anionic