Normal-to-Abnormal NHC Rearrangement of Al(III) , Ga(III) , and In(III) Trialkyl Complexes: Scope, Mechanism, Reactivity Studies, and H2 Activation.

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.

Unusual reactivity in organoaluminium and NHC chemistry: deprotonation of AlMe3 by an NHC moiety involving the formation of a sterically bulky NHC-AlMe3 Lewis adduct.

A sterically congested NHC-AlMe(3) Lewis adduct (NHC = 1,3-di-tert-butylimidazol-2-ylidene) was found to either isomerize to an "abnormal" NHC-AlMe(3) species or to be involved in the deprotonation of AlMe(3) to form the corresponding imidazolium species along with an AlMe(3)-stabilized methylene aluminium anion.

Versatile coordination modes of novel hemilabile S-NHC ligands.

The Ag(I) and hemilabile Pd(II) carbene complexes obtained from novel thioether-functionalized imidazolium salts synthesised in one-step illustrate the diversity of coordination modes of these new S, C(NHC) ligands.