284490-39-7Relevant articles and documents
A Multifunctional Pincer Ligand Supports Unsaturated Cobalt: Five Functionalities in One Pincer
Polezhaev, Alexander V.,Chen, Chun-Hsing,Losovyj, Yaroslav,Caulton, Kenneth G.
, p. 8039 - 8050 (2017)
A pyridyl pincer ligand was developed to incorporate steric bulk, through a PtBu2 arm, and proton responsivity, through a pyrazole pincer ligand arm, together with reactivity at benzylic hydrogen and redox activity within a 1,4 diazabutadiene moiety. Binding it to CoCl2 yielded square-pyramidal [(PNNH)CoCl2], which was deprotonated by Li[N(SiMe3)2] to form [{Li(THF)2PNN}CoCl2]. Reduction of this LiCl adduct with KC8 under CO atmosphere led to formation of CoI mono- and dicarbonyl complexes, which can be protonated but also further deprotonated at the benzylic CH group to give a dearomatized pyridyl group. The ligand was characterized in its neutral, monoanionic, and dianionic forms, and the anions were shown to exist as intimate ion pairs with Li+ bound to pyrazolate N and chloride bound to Lewis acidic cobalt. X-ray photoelectron spectroscopy was used to assay both Li content and cobalt oxidation states. The general character of binding of LiCl to a metal complex acidic at metal and nucleophilic at ligand (pyrazolate Nβ) is discussed, as are potential catalytic applications of the concept.
