d–d Dative Bonding Between Iron and the Alkaline‐Earth Metals Calcium,Strontium, and Barium |
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Authors: | Philipp Stegner Christian Frber Jan Oetzel Ulrich Siemeling Michael Wiesinger Jens Langer Sudip Pan Nicole Holzmann Gernot Frenking Uta Albold Biprajit Sarkar Sjoerd Harder |
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Institution: | Philipp Stegner,Christian Färber,Jan Oetzel,Ulrich Siemeling,Michael Wiesinger,Jens Langer,Sudip Pan,Nicole Holzmann,Gernot Frenking,Uta Albold,Biprajit Sarkar,Sjoerd Harder |
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Abstract: | Double deprotonation of the diamine 1,1′‐(tBuCH2NH)‐ferrocene ( 1 ‐H2) by alkaline‐earth (Ae) or EuII metal reagents gave the complexes 1 ‐Ae (Ae=Mg, Ca, Sr, Ba) and 1 ‐Eu. 1 ‐Mg crystallized as a monomer while the heavier complexes crystallized as dimers. The Fe???Mg distance in 1 ‐Mg is too long for a bonding interaction, but short Fe???Ae distances in 1 ‐Ca, 1 ‐Sr, and 1 ‐Ba clearly support intramolecular Fe???Ae bonding. Further evidence for interactions is provided by a tilting of the Cp rings and the related 1H NMR chemical‐shift difference between the Cp α and β protons. While electrochemical studies are complicated by complex decomposition, UV/Vis spectral features of the complexes support Fe→Ae dative bonding. A comprehensive bonding analysis of all 1 ‐Ae complexes shows that the heavier species 1 ‐Ca, 1 ‐Sr, and 1 ‐Ba possess genuine Fe→Ae bonds which involve vacant d‐orbitals of the alkaline‐earth atoms and partially filled d‐orbitals on Fe. In 1 ‐Mg, a weak Fe→Mg donation into vacant p‐orbitals of the Mg atom is observed. |
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Keywords: | alkaline-earth metals ferrocene metal– metal bonding theoretical chemistry |
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