Complexation and Versatile Reactivity of a Highly Lewis Acidic Cationic Mg Complex with Alkynes and Phosphines

Journal article


Publication Details

Author(s): Pahl J, Stennett T, Volland M, Guldi DM, Harder S
Journal: Chemistry - A European Journal
Publication year: 2019
Volume: 25
Journal issue: 8
Pages range: 2025-2034
ISSN: 0947-6539
eISSN: 1521-3765


Abstract

[(BDI)Mg+][B(C6F5)(4)(-)] (1; BDI=CH[C(CH3)NDipp](2); Dipp=2,6-diisopropylphenyl) was prepared by reaction of (BDI)MgnPr with [Ph3C+][B(C6F5)(4)(-)]. Addition of 3-hexyne gave [(BDI)Mg+(EtCCEt)][B(C6F5)(4)(-)]. Single-crystal X-ray analysis, NMR investigations, Raman spectra, and DFT calculations indicate a significant Mg-alkyne interaction. Addition of the terminal alkynes PhCCH or Me3SiCCH led to alkyne deprotonation by the BDI ligand to give [(BDI-H)Mg+(CCPh)](2)2[B(C6F5)(4)(-)] (2, 70%) and [(BDI-H)Mg+(CCSiMe3)](2)2[B(C6F5)(4)(-)] (3, 63%). Addition of internal alkynes PhCCPh or PhCCMe led to [4+2] cycloadditions with the BDI ligand to give {Mg+C(Ph)=C(Ph)C[C(Me)=NDipp](2)}(2) 2[B(C6F5)(4)(-)] (4, 53%) and {Mg+C(Ph)=C(Me)C[C(Me)=NDipp](2)}(2)2[B(C6F5)(4)(-)] (5, 73%), in which the Mg center is N,N,C-chelated. The (BDI)Mg+ cation can be viewed as an intramolecular frustrated Lewis pair (FLP) with a Lewis acidic site (Mg) and a Lewis (or BrOnsted) basic site (BDI). Reaction of [(BDI)Mg+][B(C6F5)(4)(-)] (1) with a range of phosphines varying in bulk and donor strength generated [(BDI)Mg+PPh3][B(C6F5)(4)(-)] (6), [(BDI)Mg+PCy3][B(C6F5)(4)(-)] (7), and [(BDI)Mg+ PtBu3][B(C6F5)(4)(-)] (8). The bulkier phosphine PMes(3) (Mes=mesityl) did not show any interaction. Combinations of [(BDI)Mg+][B(C6F5)(4)(-)] and phosphines did not result in addition to the triple bond in 3-hexyne, but during the screening process it was discovered that the cationic magnesium complex catalyzes the hydrophosphination of PhCCH with HPPh2, for which an FLP-type mechanism is tentatively proposed.


FAU Authors / FAU Editors

Guldi, Dirk Michael Prof. Dr.
Lehrstuhl für Physikalische Chemie I
Harder, Sjoerd Prof. Dr.
Stennett, Thomas Dr.
Lehrstuhl für Anorganische und Metallorganische Chemie
Pahl, Jürgen
Lehrstuhl für Anorganische und Metallorganische Chemie
Lehrstuhl für Anorganische und Metallorganische Chemie
Volland, Michel
Lehrstuhl für Physikalische Chemie I


How to cite

APA:
Pahl, J., Stennett, T., Volland, M., Guldi, D.M., & Harder, S. (2019). Complexation and Versatile Reactivity of a Highly Lewis Acidic Cationic Mg Complex with Alkynes and Phosphines. Chemistry - A European Journal, 25(8), 2025-2034. https://dx.doi.org/10.1002/chem.201804802

MLA:
Pahl, Jürgen, et al. "Complexation and Versatile Reactivity of a Highly Lewis Acidic Cationic Mg Complex with Alkynes and Phosphines." Chemistry - A European Journal 25.8 (2019): 2025-2034.

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Last updated on 2019-01-03 at 10:08