Understanding the Effect of Ancillary Ligands on Concerted
Metalation–Deprotonation by (<sup>dm</sup>Phebox)Ir(OAc)<sub>2</sub>(H<sub>2</sub>O) Complexes: A DFT Study
- Publication date
- Publisher
Abstract
A DFT
study of (<sup>dm</sup>Phebox)Ir(OAc)<sub>2</sub>(H<sub>2</sub>O)
was undertaken to understand ligand effects that control the propensity
of this complex to undergo intermolecular alkane C–H activation
by a concerted metalation–deprotonation (CMD) mechanism. Substitution
of electronically diverse substituents at the <i>para</i> position of the aryl ring and exchange of the pincer oxazolinyl
arms with other donor groups were calculated to minimally impact the
barriers to C–H activation. It is suggested that these modifications
do not influence the orbitals directly involved in the six-membered
CMD transition state. The base and spectator carboxylate ligands were
calculated to play two distinct roles in the activation with different
electronic preferences, namely, their intrinsic basicity and <i>trans</i> influence/effect, respectively. Heteroaryl linkers
in the pincer backbone were identified as a promising lead, yielding
noticeably lower computed C–H activation barriers, due to increased
electrophilicity of the cationic metal center
