Yttrium-Catalyzed Amine–Silane Dehydrocoupling: Extended Reaction Scope with a Phosphorus-Based Ligand

The
scope of the catalytic dehydrocoupling of primary and secondary
amines with phenylsilanes has been investigated using [Y­{N­(SiMe3)2}3] and a four-coordinate analogue
bearing a cyclometalated phosphonium methylide ligand. Inclusion of
the phosphorus-based ligand on yttrium results in increased substrate
scope in comparison to the tris­(amide) analogue. While reversible
C–H bond activation of the cyclometalated ligand was observed
in stoichiometric experiments, D-labeling experiments and DFT calculations
suggest that reversible ligand activation is not involved in silazane
formation under catalytic conditions. We suggest that the extended
reaction scope with the four-coordinate yttrium phosphonium methylide
complex relative to the three-coordinate yttrium (tris)­amide complex
is a result of differences in the ease of amine inhibition of catalysis.