The electronic structures of a series of low-coordinate iron-phosphido complexes were assessed through a combined field-dependent 57Fe Mössbauer, high-frequency electron paramagnetic resonance (HFEPR), and magnetic susceptibility and magnetization data. Specifically, we have studied [LFeII(η1-Me3SiP-P-t-Bu2)] (1) and [LFeII(η2-i-Pr2P-P-SiMe3)] (2) where L = β-diketiminate. Single-crystal X-ray crystallography revealed that while 1 exhibits a three-coordinated 2 features a four-coordinated iron site. For 2 the increase in the coordination number is induced by the change from an anticlinal to a synclinal conformation of the phosphanylphosphido ligands. Our studies revealed that 1 and 2 have a high-spin iron(II) site with S = 2 ground states that have distinct properties. Thus, 1 exhibits a zero-field splitting (ZFS) described by a positive D parameter whereas for 2 this parameter is negative. Density functional theory (DFT) and time-dependent (TD) DFT calculations provided insight into the origin of the observed differences and allowed us to rationalize the experimental fine and hyperfine structure parameters.

Assessing the magnetic properties of low-coordinate iron(II) complexes supported by β-diketiminate ligands and phosphorus-based co-ligands

2019 Spring National Meeting

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