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Effectiveness of the Oxygenation over Classical Protonolysis Reactions: A Case of Alkylzinc Complexes Incorporating an Aminoalcoholate Ligand
Authors:Dr. Karolina Zelga  Dr. Tomasz Pietrzak  Dr. Tomasz Han  Dr. Iwona Justyniak  Dr. Elżbieta Chwojnowska  Prof. Piotr Sobota  Prof. Janusz Lewiński
Affiliation:1. Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland;2. Faculty of Chemistry, University of Wrocław Polish Academy of Science, F. Joliot-Curie ‘4, 50-383 Wrocław, Poland;3. Institute of Physical Chemistry, Polish Academy of Science, Kasprzaka 44/52, 01-224 Warsaw, Poland
Abstract:Alkylzinc aminoalcoholates have emerged as powerful catalysts in organic synthesis and polymerization processes. Despite extensive research, difficulties in the rational design of these catalytic systems and in-depth understanding of their modes of action have hitherto been encountered. Most of the major obstacles stem largely from the relatively limited knowledge of the structure-activity relationship of zinc catalysts. In fact, the key active species are often generated in situ via the protonolysis of the alkylzinc precursors, which precludes their isolation and detailed characterization. Herein, the effectiveness of the oxygenation over the classical protonolysis in the synthesis of zinc alkylperoxides stabilized by an aminoalcoholate ligand is demonstrated. The controlled oxygenation of a tert-butylzinc complex incorporating a pridinolum (prinol) ligand leads to well-defined a dinuclear adduct of a (prinol)ZnOOtBu moiety with the parent tBuZn(prinol) complex and a novel dimer [tBuOOZn(prinol)]2 with terminal alkylperoxide groups. The observed reaction outcomes strongly depend on the reaction conditions. Although sparse examples of heteroleptic adducts of the [RZn(L)]x[ROOZn(L)]y-type are known, the herein reported homoleptic [ROOZn(L)]x aggregate is unprecedented. Strikingly, comparative studies involving reactions between tBuZn(prinol) and tert-butylhydroperoxide or ethanol revealed that the respective seemingly simple zinc alkylperoxides, or zinc alkoxides, respectively, are not accessible via the classical alcoholysis. We believe that these game-changing results concerning multifaceted chemistry of organozinc aminoalcoholates should pave the way for more rational development of various Zn-based catalytic systems.
Keywords:alkylperoxide  dioxygen  oxygenation  protonolysis  zinc
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