Chiral‐at‐Molybdenum – A Computational Study on N‐Substituted cis‐MoO₂(nacnac)₂

Abstract

Cis‐MoO2(nacnac)2 (nacnac=β‐diketiminate) can be a viable chiral‐at‐metal catalyst when its two β‐diketiminate (nacnac) ligands are N‐substituted to prevent Λ⇌Δ racemization. Even simple methyl groups raise the barriers for racemization significantly for the Bailar, Rây‐Dutt, Conte‐Hippler, and Dhimba‐Muller‐Lammertsma (DML) twists to a respectable 28.5, 37.8, 30.5, and 25.1 kcal/mol, respectively, at ωB97X‐D/6‐311+G(2d,p) (LANL2DZ for Mo) including acetonitrile solvation. The lowest energy DML barrier increases to ΔGo=27.4 kcal/mol with N‐substituted t‐butyl groups. The nacnac ligands’ electronic and steric components to the racemization barriers are discussed.