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Mono‐ and Dinuclear Bioxazoline–Palladium Complexes for the Stereocontrolled Synthesis of CO/Styrene Polyketones
Author(s) -
Scarel Alessandro,
Durand Jérôme,
Franchi Davide,
Zangrando Ennio,
Mestroni Giovanni,
Carfagna Carla,
Mosca Luca,
Seraglia Roberta,
Consiglio Giambattista,
Milani Barbara
Publication year - 2005
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.200500410
Subject(s) - palladium , styrene , copolymer , chemistry , chelation , polymer chemistry , ligand (biochemistry) , hydroquinone , tacticity , nuclear magnetic resonance spectroscopy , isopropyl , stereochemistry , medicinal chemistry , catalysis , organic chemistry , polymer , polymerization , biochemistry , receptor
The coordination chemistry of the chiral bioxazoline ligand (4 S ,4′ S )‐2,2′‐bis(4‐isopropyl‐4,5‐dihydrooxazole) to Pd II provides evidence that the ligand bonding can occur either through chelation of one Pd II ion leading to a mononuclear species with the expected cis geometry, or by double bridging of two Pd II ions giving a dinuclear complex with trans geometry. The species in solution are identified by 1 H NMR spectroscopy. Both the mononuclear and the dinuclear complexes promote the CO/styrene copolymerization, yielding the corresponding polyketone with a fully or a predominantly isotactic microstructure, depending on the reaction medium. The nature of the anion present in the palladium precatalysts affects the polyketone stereochemistry. MALDI‐TOF analysis of the copolymers synthesized reveals the presence of p ‐hydroxyphenolic end‐groups, thus confirming and explaining the role of 1,4‐hydroquinone as a molecular weight regulator.