Spin States, Bonding and Magnetism in Mixed‐Valence Iron(0)‐Iron(II) Complexes. Issue 11 (12th January 2022)

• Record Type: Journal Article
• Authors: Kim, Daniel; Wilson, Daniel W. N.; Fataftah, Majed S.; Mercado, Brandon Q.; Holland, Patrick L.
• Is Part Of: Chemistry. Volume 28:Issue 11(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-12
• Subjects: Iron -- magnetism -- metal-metal bonds -- xenophilic complexes; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202104431
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: "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, L x Fe−Fp (L X = β‐aldiminate or β‐diketiminate; Fp = Fe(CO)2 Cp), that offer insight into Fe−Fe bonding. Mössbauer, magnetism, and DFT analysis indicate that the most accurate electronic structure description is LFe II ←Fe 0 (CO)2 Cp, in which the Fe(CO)2 Cp 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. Abstract : The nature of metal‐metal bonding between two different kinds of metal sites is essential for understanding these "xenophilic" complexes. We used Mössbauer spectroscopy, SQUID magnetometry and computational analysis on a pair of related diiron complexes; they indicated that the bond order is roughly one‐half. The best electronic structure description is LFe II −Fe 0 (CO)2 Cp, in which the Fe(CO)2 Cp is low‐spin iron(0) and acts as an X‐type ligand toward the high‐spin iron(II) of the LFe fragment.