Spin States, Bonding and Magnetism in Mixed‐Valence Iron(0)‐Iron(II) Complexes**.

Kim, Daniel; Wilson, Daniel W. N.; Fataftah, Majed S.; Mercado, Brandon Q.; Holland, Patrick L.

"Xenophilic" complexes offer metal‐metal bonds between disparate metal sites, but the nature of the metal‐metal bonding is often unclear. Here, we describe two novel complexes with unsupported Fe−Fe bonds, LxFe−Fp (LX = β‐aldiminate or β‐diketiminate; Fp = Fe(CO)2Cp), that offer insight into Fe−Fe bonding. Mössbauer, magnetism, and DFT analysis indicate that the most accurate electronic structure description is LFeII←Fe0(CO)2Cp, in which the Fe(CO)2Cp is low‐spin iron(0) and acts as an X‐type ligand toward the high‐spin iron(II) of the LFe fragment. This largely electrostatic interaction has a bond order of only 0.5. The three‐coordinate high‐spin iron(II) site has large zero‐field splitting, and in addition its Mössbauer parameters can be used to rank the Fp− "metalloligand" as a donor; it is nearly as strong a donor as phosphides and alkyls.

METAL-metal bonds; MAGNETISM; MOSSBAUER effect; ELECTROSTATIC interaction; ELECTRONIC structure; IRON

Chemistry - A European Journal, 2022, Vol 28, Issue 10, p1

0947-6539

Academic Journal

10.1002/chem.202104431