Dataset Information

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

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

Stegner Philipp P Färber Christian C Oetzel Jan J Siemeling Ulrich U Wiesinger Michael M Langer Jens J Pan Sudip S Holzmann Nicole N Frenking Gernot G Albold Uta U Sarkar Biprajit B Harder Sjoerd S

Angewandte Chemie (International ed. in English) 20200702 34

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 ...[more]

PMID: 32463527

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Project description:Bond-length distributions have been examined for 55 configurations of alkali-metal ions and 29 configurations of alkaline-earth-metal ions bonded to oxygen, for 4859 coordination polyhedra and 38?594 bond distances (alkali metals), and for 3038 coordination polyhedra and 24?487 bond distances (alkaline-earth metals). Bond lengths generally show a positively skewed Gaussian distribution that originates from the variation in Born repulsion and Coulomb attraction as a function of interatomic distance. The skewness and kurtosis of these distributions generally decrease with increasing coordination number of the central cation, a result of decreasing Born repulsion with increasing coordination number. We confirm the following minimum coordination numbers: ([3])Li(+), ([3])Na(+), ([4])K(+), ([4])Rb(+), ([6])Cs(+), ([3])Be(2+), ([4])Mg(2+), ([6])Ca(2+), ([6])Sr(2+) and ([6])Ba(2+), but note that some reported examples are the result of extensive dynamic and/or positional short-range disorder and are not ordered arrangements. Some distributions of bond lengths are distinctly multi-modal. This is commonly due to the occurrence of large numbers of structure refinements of a particular structure type in which a particular cation is always present, leading to an over-representation of a specific range of bond lengths. Outliers in the distributions of mean bond lengths are often associated with anomalous values of atomic displacement of the constituent cations and/or anions. For a sample of ([6])Na(+), the ratio Ueq(Na)/Ueq(bonded anions) is partially correlated with ?([6])Na(+)-O(2-)? (R(2) = 0.57), suggesting that the mean bond length is correlated with vibrational/displacement characteristics of the constituent ions for a fixed coordination number. Mean bond lengths also show a weak correlation with bond-length distortion from the mean value in general, although some coordination numbers show the widest variation in mean bond length for zero distortion, e.g. Li(+) in [4]- and [6]-coordination, Na(+) in [4]- and [6]-coordination. For alkali-metal and alkaline-earth-metal ions, there is a positive correlation between cation coordination number and the grand mean incident bond-valence sum at the central cation, the values varying from 0.84?v.u. for ([5])K(+) to 1.06?v.u. for ([8])Li(+), and from 1.76?v.u. for ([7])Ba(2+) to 2.10?v.u. for ([12])Sr(2+). Bond-valence arguments suggest coordination numbers higher than [12] for K(+), Rb(+), Cs(+) and Ba(2+).

Dataset Information

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

Publications

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

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