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A Multifunctional Pincer Ligand Supports Unsaturated Cobalt: Five Functionalities in One Pincer
Author(s) -
Polezhaev Alexander V.,
Chen ChunHsing,
Losovyj Yaroslav,
Caulton Kenneth G.
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201700859
Subject(s) - chemistry , pincer movement , ligand (biochemistry) , deprotonation , medicinal chemistry , cobalt , reactivity (psychology) , pincer ligand , adduct , moiety , photochemistry , phosphine , steric effects , protonation , nitromethane , stereochemistry , inorganic chemistry , catalysis , organic chemistry , ion , medicine , biochemistry , receptor , alternative medicine , pathology
A pyridyl pincer ligand was developed to incorporate steric bulk, through a P t Bu 2 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 CoCl 2 yielded square‐pyramidal [(PNNH)CoCl 2 ], which was deprotonated by Li[N(SiMe 3 ) 2 ] to form [{Li(THF) 2 PNN}CoCl 2 ]. Reduction of this LiCl adduct with KC 8 under CO atmosphere led to formation of Co I 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.