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Aluminum−Nitrogen Rings and Cages with Organic Handles: A Theoretical Study

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journal contribution
posted on 2009-04-09, 00:00 authored by Cong Trinh, Alexey Y. Timoshkin, Gernot Frenking
The structures and stability of monomeric and oligomeric compounds resulting from the elimination of 2 mol of HBr from the AlBr3en complex have been studied theoretically at the B3LYP/LANL2DZ(d,p) level of theory. Two series of the ring and cage oligomer compounds were considered: imino [AlBrNCH2CH2NH2]n, n = 1−4, 6 (In), and isomeric amido [AlBrNHCH2CH2NH]n, n = 1−3 (A′n), species. In all cases the amido isomers are 95−295 kJ mol−1 more stable compared to their imino counterpairs. Intramolecular donor−acceptor interactions play an important role in the stabilization of the structure. Possible pathways of the polymerization have also been explored. Although the generation of the oligomers via HBr elimination in the gas phase is predicted to be thermodynamically unfavorable, operation of such reactions in the condensed phase is feasible. Substitution of bromine by hydrogen makes H2 elimination reactions thermodynamically favorable. This opens a perspective for the synthesis of novel ladder-type oligomers with a continuous (AlN)n core supported by C2H4 balustrade and imino cages with C2H4 handles.