Hydroboration of Aldehydes, Ketones, and Carbodiimides Promoted by Mono(imidazolin-2-iminato) Hafnium Complexes

Abstract

Imidazolin-2-iminato hafnium complexes of the type [(ImRN)Hf(CH2Ph)3] were synthesized (ImtBuN = 1,3-di-tert-butylimidazolin-2-iminato); ImDippN = 1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-iminato. The complexes were crystallized and structurally characterized. Despite the oxophilicity of the hafnium center, both hafnium complexes were catalytically active in the hydroboration of aldehydes, ketones, and carbodiimides. Herein, we present the influence of different substrates bearing electron-withdrawing or electron-donating groups on the catalytic reactions. Based on stoichiometric reaction in each process, plausible mechanistic scenarios are presented.