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Issue 11, 2017
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“Masked” Lewis-acidity of an aluminum α-phosphinoamide complex

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The reaction of Ph2P(DIPP)NH with AlMe3 cleanly gives an aluminum amide complex that crystallizes as a centrosymmetric dimer with a six-membered Al–N–P–Al–N–P ring. In aromatic solvents the dimer remains intact but the Al–P bond is readily broken upon addition of THF to form Ph2P(DIPP)NAlMe2·THF. Efforts to use [Ph2P(DIPP)NAlMe2]2 as a “masked” Lewis acidic activator for olefin polymerization catalysts were unsuccessful but the complex showed a Frustrated Lewis pair reactivity instead. The P/Al complex reacts with isocyanates to give the C[double bond, length as m-dash]O inserted product that crystallizes as a five-membered ring system Al–O–C(NR)–P–N. The reaction of [Ph2P(DIPP)NAlMe2]2 with CO2, however, gave an insertion in the N–Al bond and the dimeric product [Ph2P(DIPP)NCO2AlMe2]2 was isolated. The dimer [Ph2P(DIPP)NAlMe2]2 is one of the few Al/P FLPs that can activate C[double bond, length as m-dash]C double bonds irreversibly. A reaction with allyl methyl sulfide and 1-hexene led to the clean formation of the structurally similar activated alkene products [(DIPP)N-Ph2P-CH(CH2SMe)CH2]AlMe2 and [(DIPP)N-Ph2P-CH(C4H9)CH2]AlMe2.

Graphical abstract: “Masked” Lewis-acidity of an aluminum α-phosphinoamide complex

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Supplementary files

Article information

26 Jan 2017
13 Feb 2017
First published
28 Feb 2017

Dalton Trans., 2017,46, 3601-3610
Article type

“Masked” Lewis-acidity of an aluminum α-phosphinoamide complex

H. S. Zijlstra, J. Pahl, J. Penafiel and S. Harder, Dalton Trans., 2017, 46, 3601
DOI: 10.1039/C7DT00318H

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