Affiliation:
1. Department of Chemical Sciences University of Johannesburg Auckland Park Johannesburg 2006 South Africa
2. Department of Chemistry and Pharmaceutical Sciences Faculty of Sciences Vrije Universiteit Amsterdam De Boelelaan 1108 1081 HZ Amsterdam (The Netherlands
Abstract
AbstractCis‐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.
Funder
National Research Foundation