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Abstract:
A synthetic strategy for the preparation of novel doubly yldiide bridged iron(II) high spin dimers ([(mu(2)-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 mu(2)-C yldiide ligands in [(mu(2)-C)FeL](2). The comprehensive structural and electronic analysis of dimers [(mu(2)-C)FeL](2), including NMR, Mossbauer, and X-ray spectroscopy, as well as X-ray crystallography, SQUID, and DFT calculations, confirm their high-spin Fe-II configurations. Interestingly, the Fe2C2 cores display very acute Fe-C-Fe angles (averaged: 78.6(2)degrees) resulting in short Fe center dot center dot center dot Fe distances (averaged: 2.588(2) angstrom). 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 mu(2)-C yldiide ligands.
