Mono- and dinuclear bioxazoline-palladium complexes for the stereocontrolled synthesis of CO/styrene polyketones.
The coordination chemistry of the chiral bioxazoline ligand (4S,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 1H 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.
Scarel
Alessandro
A
Dipartimento di Scienze Chimiche,Università di Trieste, Via Licio Giorgieri 1, 34127 Trieste, Italy.
Durand
Jérôme
J
Franchi
Davide
D
Zangrando
Ennio
E
Mestroni
Giovanni
G
Carfagna
Carla
C
Mosca
Luca
L
Seraglia
Roberta
R
Consiglio
Giambattista
G
Milani
Barbara
B