Speaker: Prof. Ajay Venugopal
Indian Institute of Science Education and Research
Thiruvananthapuram
Title: “Trans-Effects in Sb and Bi Lewis Acids: Implications
in Catalysis.”
Day and Date: Thursday, February 16, 2023
Time: 3.00 pm.
Venue: Room no. 350, Chemistry Department
Second floor, Annex
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Hosted by Prof. Ramaswamy Murugavel
Abstract Salts of heavier pnictogens (Pn), antimony, and bismuth in +3 oxidation state commonly find application as
Lewis acids in organic synthesis.[1] Common examples of these salts include chlorides, carboxylates, and
trifluoromethanesulfonate. A qualitative model for the origin of Lewis acidity in Sb(III) and Bi(III)
compounds was proposed by Norman in 1994.[2] According to this model, a polarized Pn–X bond has a
corresponding low-lying antibonding σ*-orbital that can accept a pair of electrons. The Pn–X bonds
constitute the primary bonds, while the interaction between antibonding orbitals and Lewis bases constitutes
the secondary bonding. The energy levels of the antibonding orbitals and the Lewis acidity of PnX3 depend
on the extent of polarization in primary bonds. Ligand choice determines the tuning of the σ* orbital energy
providing a tool to control the Lewis acidity in antimony and bismuth Lewis acids. Based on our recent
findings, this presentation will provide insights into the ligand effects as a design parameter to access new
antimony and bismuth Lewis acids.[3] Catalytic hydrosilylation and carbonyl olefin metathesis are
demonstrated as proof of our concept.