D-d Dative Bonding Between Iron and the Alkaline-Earth Metals Calcium, Strontium, and Barium.

ABSTRACT: Double deprotonation of the diamine 1,1'-(tBuCH2 NH)-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 1 H?NMR chemical-shift difference between the Cp ? and ? 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.

SUBMITTER: Stegner P 

PROVIDER: S-EPMC7496664 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature