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From Ylides to Doubly Yldiide-Bridged Iron(II) High Spin Dimers via Self-Protolysis

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journal contribution
posted on 01.07.2019, 18:08 by Sivathmeehan Yogendra, Thomas Weyhermüller, Anselm W. Hahn, Serena DeBeer
A synthetic strategy for the preparation of novel doubly yldiide bridged iron­(II) high spin dimers ([(μ2-C)­FeL]2, L = N­(SiMe3)2, Mesityl) has been developed. This includes the synthesis of ylide-iron­(II) monomers [(Ylide)­FeL2] via adduct formation. Subsequent self-protolysis at elevated temperatures by in situ deprotonation of the ylide ligands results in a dimerization reaction forming the desired bridging μ2-C yldiide ligands in [(μ2-C)­FeL]2. The comprehensive structural and electronic analysis of dimers [(μ2-C)­FeL]2, including NMR, Mössbauer, and X-ray spectroscopy, as well as X-ray crystallography, SQUID, and DFT calculations, confirm their high-spin FeII configurations. Interestingly, the Fe2C2 cores display very acute Fe–C–Fe angles (averaged: 78.6(2)°) resulting in short Fe···Fe distances (averaged: 2.588(2) Å). A remarkably strong antiferromagnetic coupling between the Fe centers has been identified. Strongly polarized Fe–C bonds are observed where the negative charge is mostly centered at the μ2-C yldiide ligands.