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Flexible Coordination of N,P-Donor Ligands in Aluminum Dimethyl and Dihydride Complexes
dataset
posted on 2019-08-14, 12:34 authored by Rosalyn L. Falconer, Gary S. Nichol, Michael J. CowleyAluminum hydrides, once a simple
class of stoichiometric reductants, are now emerging as powerful catalysts
for organic transformations such as the hydroboration or hydrogenation
of unsaturated bonds. The coordination chemistry of aluminum hydrides
supported by P donors is relatively underexplored. Here, we report
aluminum dihydride and dimethyl complexes supported by amidophosphine
ligands and study their coordination behavior in solution and in the
solid state. All complexes exist as κ2-N,P complexes
in the solid state. However, we find that for amidophosphine ligands
bearing bulky aminophosphine donors, aluminum dihydride and dimethyl
complexes undergo a “ligand-slip” rearrangement in solution
to generate κ2-N,N complexes. Thus, importantly for
catalytic activity, we find that the coordination behavior of the
P donor can be modulated by controlling its steric bulk. We show that
the reported aluminum hydrides catalyze the hydroboration of alkynes
by HBPin and that the variable coordination mode exhibited by the
amidophosphine ligand modulates the catalytic activity.