NHC-Stabilized Al(III) and Ga(III) Cationic Alkyls : Synthesis, Structure and Use in Hydrosilylation Catalysis
Cationic Al(III) and Ga(III) species supported by N -heterocyclic carbene (NHC) ligands, (IDipp)AlMe 2 (PhBr)] + ([ 1 ] + , IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) and (IDipp)GaMe 2 ] + ([ 2 ] + ), were prepared and structurally characterized as B(C 6 F 5 ) 4 - salts via ionization of the corresponding neutral precursors (IDipp)MMe 3 (M = Al, Ga) with [Ph 3 C][B(C 6 F 5 ) 4 ] in PhBr at room temperature. Both [ 1 ][B(C 6 F 5 ) 4 ] and [ 2 ][B(C 6 F 5 ) 4 ] salt were isolated in high yield and their solid state structures established through X-ray crystallographic studies. Cations [ 1 ] + and [ 2 ] + , which are rare examples of structurally characterized tris-organyl Al(III) and Ga(III) cations, stand as potent Lewis acids as experimentally estimated through the Gutmann-Beckett method. These cations were further exploited in hydrosilylation catalysis of alkynes, benzaldehyde and CO 2 using HSiEt 3 as an hydrosilane source. Hydrosilylation of 1-hexyne, 4-phenylbutyne and phenylacetylene led to the formation of the corresponding Z-selective products 3 - 5 , respectively, while benzaldehyde was converted to PhCH 2 OSiEt 3 ( 6 ). Cations [ 1 ] + and [ 2 ] + also slowly catalyze CO 2 hydrosilylation with the selective formation of the methanol-equivalent MeOSiEt 3
Year of publication: |
[2021]
|
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Authors: | Bolley, Anaƫlle ; Specklin, David ; Dagorne, Samuel |
Publisher: |
[S.l.] : SSRN |
Saved in:
freely available
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