Metal–Ligand Cooperativity in Titanium-Catalyzed Anti-Markovnikov Hydroamination

Density
functional theory (DFT) calculations were performed to
investigate a known diamido bis­(amidate) Ti precatalyst that is excellent
for anti-Markovnikov selective alkyne hydroamination. The coordination
environments provided by the hemilabile amidate ligands were studied
to reveal their spatial and electronic influence on the structures
and energies of intermediates and transition states. Several factors
contribute to the unique regioselectivity of this catalytic system,
including orbital interactions, ligand coordination modes, and steric
repulsion. The turnover-limiting step was found to be substrate-dependent.
Experimental evidence was obtained to further test computationally
generated hypotheses. These investigations show that the bis­(amidate)
Ti catalytic system’s high regioselective performance can be
attributed to ligand hemilability, which promotes metal–ligand
cooperativity in the reaction mechanism.