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Using the Lewis Acid Me 3 Si-F-Al(OR F ) 3 To Prepare Phosphino-Phosphonium Cations with the Least-Coordinating Anion [(R F O) 3 Al-F-Al(OR F ) 3 ]
By reaction of two equivalents of Me Si-F-Al(OR ) 1 with an equimolar amount of PPh Cl, the salt [Ph P-PPh Cl] [(R O) Al-F-Al(OR ) ] 2 is prepared smoothly in 91 % yield (NMR, XRD). The synthesis of [Ph P-PPh ] [(R O) Al-F-Al(OR ) ] 3 is best achieved by a two-step reaction: first, two equivalents o...
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Published in: | Chemistry : a European journal 2017-09, Vol.23 (50), p.12305-12313 |
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Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | By reaction of two equivalents of Me
Si-F-Al(OR
)
1 with an equimolar amount of PPh
Cl, the salt [Ph
P-PPh
Cl]
[(R
O)
Al-F-Al(OR
)
]
2 is prepared smoothly in 91 % yield (NMR, XRD). The synthesis of [Ph
P-PPh
]
[(R
O)
Al-F-Al(OR
)
]
3 is best achieved by a two-step reaction: first, two equivalents of 1 react with one PPh
to give [Me
Si-PPh
]
[(R
O)
Al-F-Al(OR
)
]
4 (NMR, XRD), which, upon reaction with PPh
Cl, yields pure 3 and Me
SiCl (NMR, XRD). Typically, a stoichiometry of two equivalents of 1 with respect to one equivalent of the chloride donor should be used. Otherwise, the residual strong Lewis acidity of the [(R
O)
Al-F-Al(OR
)
]
anion in the presence of the [F-Al(OR
)
]
anion-that forms with less than two equivalents of 1-leads to further chloride exchange reactions that complicate work-up. This route presents the easiest way to introduce the least-coordinating [(R
O)
Al-F-Al(OR
)
]
anion into a system. We expect a wide use of this route in all areas, in which chloride-bond heterolysis in combination with very weakly coordinating anions is desirable. Additionally, we performed calculations on the bond dissociation mechanisms of [R
P-PMe
]
and the isoelectronic Me
P-SiMe
and Me
Si-PMe
in dependence of the solvent permittivity. These calculations show, especially for the neutral reference compounds, a heavy influence of the solvent on the dissociation mechanism, which is why we suggest investigating these properties in solution instead of gas phase. |
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ISSN: | 0947-6539 1521-3765 |
DOI: | 10.1002/chem.201701260 |