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Bonding in Low-Coordinate Environments: Electronic Structure of Distorted Square-Planar Iron-Imido Complexes With
Jeanet Conradie1, Abhik Ghosh1
1Department of Chemistry and Center for Theoretical and Computational Chemistry, University of Tromsø, N-9037 Tromsø, Norway, and Department of Chemistry, University of the Free State, 9300 Bloemfontein, Republic of South Africa.
Abstract:
Low-coordinate architectures sustain unusual chemistry for middle and late transition metals, of which imido complexes are an excellent example. Recent DFT studies have uncovered a number of unusual features in the bonding in trigonal-planar and pseudotetrahedral imido complexes. Herein, we have extended these studies to a unique, distorted square-planar iron-imido complex with a pincer-type pyridine-2,6-diimine (PDI) supporting ligand. DFT calculations indicate that the iron center in the formally Fe(II) complex Fe(PDI)(NPh) is better described as intermediate-spin Fe(III), antiferromagnetically coupled to a b2-symmetry PDI π-anion radical. A comparative analysis of the major classes of low-coordinate imido complexes has uncovered a certain similarity between Fe(PDI)(NPh) and a trigonal-planar Fe(III)-nacnac-imido complex. Both ligand architectures afford a total of four energetically accessible d orbitals, resulting in intermediate-spin Fe(III) centers.
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