Lewis acidic alkaline earth metal complexes with a perfluorinated diphenylamide ligand

Journal article


Publication Details

Author(s): Fischer C, Rösch A, Elsen H, Ballmann G, Wiesinger M, Langer J, Färber C, Harder S
Journal: Dalton Transactions
Publication year: 2019
Volume: 48
Journal issue: 20
Pages range: 6757-6766
ISSN: 1477-9226
eISSN: 1477-9234


Abstract

Alkaline earth metal (Ae) chemistry with the anion [N(C
6
F
5
)
2
]
-
has been explored. Deprotonation of the amine (C
6
F
5
)
2
NH, abbreviated in here as N
F
H, with 0.5 equivalent of AeN′′
2
(N′′ = N(SiMe
3
)
2
) is fast and gave, dependent on the solvent, the complexes AeN
F

2
, AeN
F

2
·(THF)
2
and AeN
F

2
·(Et
2
O)
2
(Ae = Mg, Ca, Sr). Using a 1/1 ratio, mixed amide complexes were obtained: N
F
AeN′′ (Ae = Mg, Ca, Sr). Crystal structures of the monomers AeN
F

2
·(THF)
2
(Ae = Mg, Ca, Sr) and AeN
F

2
·(Et
2
O)
2
(Ae = Mg, Ca) are presented and compared with those of AeN′′
2
·(THF)
2
. In addition, crystal structures of the homoleptic dimer (MgN
F

2
)
2
and the heteroleptic dimers (N
F
AeN′′)
2
(Ae = Mg, Ca, Sr) are discussed. All structures are strongly influenced by very short Ae⋯F contacts down to circa 2.11 Å (Mg), 2.50 Å (Ca) and 2.73 Å (Sr). AIM analysis illustrates that, although Ae⋯F contacts are short, there is no bond-critical-point along this axis, indicating an essentially electrostatic interaction. The monomeric complexes feature strong C
6
F
5
⋯C
6
F
5
π-stacking, resulting in unusually acute N
F
-Ae-N
F
angles as small as 95°. Heteroleptic (N
F
AeN′′)
2
complexes retain their dimeric structure in C
6
D
6
solution and there is no indication of ligand scrambling by the Schlenk equilibrium, suggesting that an electron withdrawing ligand may stabilize heteroleptic complexes. According to DFT calculations, the heteroleptic arrangement is 70 kJ mol
-1
more stable than the homoleptic dimers. The Lewis acidity of MgN
F

2
has been quantified with the Gutmann-Beckett method and by calculation of the Fluoride-Ion-Affinity. The latter calculations show that the Lewis acidity of MgN
F

2
and CaN
F

2
is comparable to that of B(C
6
F
5
)
3
. Dimeric (MgN
F

2
)
2
fully abstracts Et
3
PO from Et
3
PO·B(C
6
F
5
)
3
and may have potential in Lewis acid catalysis.


FAU Authors / FAU Editors

Ballmann, Gerd
Lehrstuhl für Anorganische und Metallorganische Chemie
Elsen, Holger
Lehrstuhl für Anorganische und Metallorganische Chemie
Färber, Christian Dr.
Lehrstuhl für Anorganische und Metallorganische Chemie
Fischer, Christian
Lehrstuhl für Anorganische und Metallorganische Chemie
Harder, Sjoerd Prof. Dr.
Lehrstuhl für Anorganische und Metallorganische Chemie
Langer, Jens Dr.
Lehrstuhl für Anorganische und Metallorganische Chemie
Rösch, Andreas
Lehrstuhl für Anorganische und Allgemeine Chemie
Wiesinger, Michael
Lehrstuhl für Anorganische und Metallorganische Chemie


How to cite

APA:
Fischer, C., Rösch, A., Elsen, H., Ballmann, G., Wiesinger, M., Langer, J.,... Harder, S. (2019). Lewis acidic alkaline earth metal complexes with a perfluorinated diphenylamide ligand. Dalton Transactions, 48(20), 6757-6766. https://dx.doi.org/10.1039/c9dt01272a

MLA:
Fischer, Christian, et al. "Lewis acidic alkaline earth metal complexes with a perfluorinated diphenylamide ligand." Dalton Transactions 48.20 (2019): 6757-6766.

BibTeX: 

Last updated on 2019-06-08 at 09:18