Ligand effects in the non-alternating CO-ethylene copolymerization by palladium(II) catalysis.
In this paper we report on a comparative study of the non-alternating CO-C(2)H(4) copolymerization catalyzed by neutral Pd(II) complexes with the phosphine-sulfonate ligands bis(o-methoxyphenyl)phosphinophenylenesulfonate and bis(o-methoxyphenyl)phosphino-ethylenesulfonate. The former ligand, featuring a lower skeletal flexibility, has been found to form more active catalysts as well as produce polyketones with higher molecular weight and higher extra-ethylene incorporation. Operando high-pressure NMR studies have allowed us to intercept, for the first time, Pd(II)(phosphine-sulfonate) beta-chelates in the non-alternating copolymerization cycle, while model organometallic reactions have contributed to demonstrate that Pd(II) (phosphine-sulfonate) fragments do not form stable carbonyl complexes. The opening of the beta-chelates has been found to be a viable process by either comonomer, which contrasts with the behaviour of Pd(II) (chelating diphosphine) catalysts for the perfectly alternating copolymerization.
Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), Area di Ricerca CNR di Firenze, via Madonna del Piano 10, 50019, Sesto Fiorentino, Italy.
Lorenzo
L
Bettucci
Claudio
C
Bianchini
Carmen
C
Claver
Eduardo J Garcia
EJ
Suarez
Aurora
A
Ruiz
Andrea
A
Meli
Werner
W
Oberhauser