A Free Aluminylene with Diverse sigma-Donating and sigma/pi-Doubly Accepting Ligand Features for Transition Metals

摘要

We report herein the synthesis, characterization, and coordination chemistry of a free N-aluminylene, namely a carbazolylaluminylene 2b. This species is prepared via a reduction reaction of the corresponding carbazolyl aluminium diiodide. The coordination behavior of 2b towards transition metal centers (W Cr) is shown to afford a series of novel aluminylene complexes 3-6 with diverse coordination modes. We demonstrate that the tri-active ambiphilic Al center in 2b can behave as: 1. a sigma-donating and doubly pi-accepting ligand; 2. a sigma-donating, sigma-accepting and pi-accepting ligand; and 3. a sigma-donating and doubly a-accepting ligand. Additionally, we show ligand exchange at the aluminylene center providing access to the modulation of electronic properties of transition metals without changing the coordinated atoms. Investigations of 2b with IDippCuCl (IDipp =1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) show an unprecedented aluminylene-alumanyl transformation leading to a rare terminal Cu-alumanyl complex 8. The electronic structures of such complexes and the mechanism of the aluminylenealumanyl transformation are investigated through density functional theory (DFT) calculations.