853576-65-5Relevant academic research and scientific papers
Trifluoroethanol: Key solvent for palladium-catalyzed polymerization reactions
Scarel, Alessandro,Durand, Jér?me,Franchi, Davide,Zangrando, Ennio,Mestroni, Giovanni,Milani, Barbara,Gladiali, Serafino,Carfagna, Carla,Binotti, Barbara,Bronco, Simona,Gragnoli, Tania
, p. 2106 - 2120 (2005)
A series of cationic palladium complexes of general formula [Pd(CH 3)(NCCH3)(N-N)][X] (N-N = phen 1, 3-sec-butyl-1,10- phenanthroline (3-sBu-phen) 2, bpy 3, (-)-(S,S)-3,3′-(1,2- dimethylethylenedioxy)-2,2′-bipyridine (bbpy) 4, (+)-(R)-3,3′-(1- methylethylenedioxy)-2,2′-bipyridine (pbpy) 5, N,N′-bis(2,6- diisopropylphenyl)-2,3-butanediimine (iso-DAB) 6; X=PF6-a, OTf (OTf = triflate) b) containing different nitrogen-donor ligands were prepared from the corresponding neutral chloro derivatives [Pd(CH3)(Cl)(N-N)] (1c-6c). They were characterized by 1H NMR spectroscopy and elemental analysis. Single crystals suitable for X-ray determination were obtained for complexes [Pd(CH3)(NCCH3)(bbpy)][PF6] (4a), [Pd(CH3)(NCCH3)(iso-DAB)][PF6] (6a) and [Pd(Cl)2(bbpy)] (4c′). The latter is the result of an exchange reaction of the methyl group, present in complex 4c, with a chloride, that occurred after dissolution of 4c in CDCl3, for 1 week at 0 °C. The catalytic behavior of complexes 1a-5a and 1b-5b in the CO/styrene copolymerization was studied in CH2Cl2 and 2,2,2-trifluoroethanol (TFE) evidencing the positive effect of the fluorinated alcohol both in terms of productivity and molecular weight values of the polymers obtained. Influence of the nitrogen ligand, the anion and the reaction time in both solvents were investigated and is discussed in detail. Encouraging preliminary results were also obtained in the synthesis of polyethylene, in TFE, catalyzed by [Pd(CH3)(NCCH3)(iso-DAB)][PF6] (6a).
New aryl α-diimine palladium(II) catalysts in stereocontrolled CO/vinyl arene copolymerization
Carfagna, Carla,Gatti, Giuseppe,Paoli, Paola,Binotti, Barbara,Fini, Francesco,Passeri, Alessandra,Rossi, Patrizia,Gabriele, Bartolo
, p. 129 - 144 (2014/02/14)
The effect of the catalyst structure on the stereoselectivity of CO/vinyl arene copolymerization has been studied with the aim of developing catalytic systems able to improve the yields while maintaining the high degree of copolymer isotacticity previously obtained using achiral nitrogen ligands. Aryl α-diimine ligands having extended aromatic rings (Ar) 2DABMe2, with Ar = 1-C10H7 (e), 1-C14H9 (f), 9-C14H9 (g), have been synthesized, and α-diimine coordination to cationic methylpalladium complexes has been investigated in solution, by means of NMR spectroscopy, and in the solid state for [Pd(Me)(NCMe)((9-C14H9) 2DABMe2)][PF6] (2g). The performance of these catalysts in CO/vinyl arene copolymerization, under mild conditions, was analyzed in terms of productivity and degree of stereoregularity of the resulting polyketones. In comparison with previous results, a remarkable enhancement in the yield of isotactic copolymer was observed using the new achiral 9-anthryl α-diimine ligand g, confirming that the ortho disubstitution and the extended aromatic rings play key roles in obtaining good stereoselectivity and good productivity. To perform a structural analysis of the first steps of the CO/p-methylstyrene copolymerization, complex [Pd(Me)(CO)((9-C14H9)2DABMe2)] [BAr′4] (3g) was used as a starting point: NMR investigation reveals the stereoselective formation of the olefin/CO/olefin insertion product (6g), which prevalently exists in solution in only one diastereoisomeric form, thus justifying the observed high polymer isotacticity.
