Subtle Reactivities of Boron and Aluminum Complexes with Amino-Linked N-Heterocyclic Carbene Ligation

This paper describes the synthesis and characterization of trimethylaluminum ( 2a ), dimethylaluminum ( 3a ), and triphenylboron complexes ( 7 ) supported by functional amine-linked NHC ligands. The chemical reactivity studies with carbodiimide and isocyanate were preformed with 2a and 3a, illustrating the noninnocent nature in Al–carbene bonding. However, the boron–carbene interaction is quite robust against addition of these substrates even at higher temperature conditions. The subtle difference in chemical reactivity between aluminum and boron is attributed from the metal–carbene bond covalency. Development of the catalytic method for Suzuki–Miyaura coupling utilizing triphenylboron reagent supported by amino-NHC is also presented.