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Redox-Noninnocent Ligand-Supported Vanadium Catalysts for the Chemoselective Reduction of CX (X = O, N) Functionalities

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journal contribution
posted on 12.09.2019, 15:35 by Guoqi Zhang, Jing Wu, Shengping Zheng, Michelle C. Neary, Jincheng Mao, Marco Flores, Ryan J. Trovitch, Pavel A. Dub
Catalysis is the second largest application for V after its use as an additive to improve steel production. Molecular complexes of vanadium­(V) are particularly useful and efficient catalysts for oxidation processes; however, their ability to catalyze reductive transformations has yet to be fully explored. Here we report the first examples of polar organic functionality reduction mediated by V. Open-shell VIII complexes that feature a π-radical monoanionic 2,2′:6′,2″-terpyridine ligand (Rtpy) functionalized at the 4′-position (R = (CH3)3SiCH2, C6H5) catalyze mild and chemoselective hydroboration and hydrosilylation of functionalized ketones, aldehydes, imines, esters, and carboxamides with turnover numbers (TONs) of up to ∼1000 and turnover frequencies (TOFs) of up to ∼500 h–1. Computational evaluation of the precatalyst synthesis and activation has revealed underappreciated complexity associated with the redox-active tpy chelate.