Normal‐to‐Abnormal NHC Rearrangement of AlIII,GaIII, and InIII Trialkyl Complexes: Scope,Mechanism, Reactivity Studies,and H2 Activation |
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Authors: | Dr. Gilles Schnee Prof. Olalla Nieto Faza Dr. David Specklin Dr. Béatrice Jacques Dr. Lydia Karmazin Prof. Richard Welter Prof. Carlos Silva López Dr. Samuel Dagorne |
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Affiliation: | 1. Institut de Chimie de Strasbourg, CNRS‐Université de Strasbourg, 1 rue Blaise Pascal, 67000 Strasbourg (France);2. Depto. Química Orgánica, Universidade de Vigo, Facultade de Ciencias, Campus As Lagoas, 32004, Ourense (Spain);3. Service de Radiocristallographie, Institut de Chimie de Strasbourg, CNRS‐Université de Strasbourg, 1 rue Blaise Pascal, 67000 Strasbourg (France);4. Institut of Plant Molecular Biology, CNRS UPR 2357, 28 rue Goethe, 67083 Strasbourg Cedex (France) |
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Abstract: | The present contribution reports experimental and theoretical mechanistic investigations on a normal‐to‐abnormal (C2‐to‐C4‐bonded) NHC rearrangement processes occurring with bulky group 13 metal NHC adducts, including the scope of such a reactivity for Al compounds. The sterically congested adducts (nItBu)MMe3 (nItBu=1,3‐di‐tert‐butylimidazol‐2‐ylidene; M=Al, Ga, In; 1 a – c ) readily rearrange to quantitatively afford the corresponding C4‐bonded complexes (aItBu)MMe3 ( 4 a – c ), a reaction that may be promoted by THF. Thorough experimental data and DFT calculations were performed on the nNHC‐to‐aNHC process converting the Al‐nNHC ( 1 a ) to its aNHC analogue 4 a . A nItBu/aItBu isomerization is proposed to account for the formation of the thermodynamic product 4 a through reaction of transient aItBu with THF–AlMe3. The reaction of benzophenone with (nItBu)AlMe3 afforded the zwitterionic species (aItBu)(CPh2‐O‐AlMe3) ( 6 ), reflecting the unusual reactivity that such bulky adducts may display. Interestingly, the nItBu/Al(iBu)3 Lewis pair behaves like a frustrated Lewis pair (FLP) since it readily reacts with H2 under mild conditions. This may open the way to future reactivity developments involving commonly used trialkylaluminum precursors. |
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Keywords: | aluminum gallium indium mesoionic carbenes N‐heterocyclic carbenes |
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