Ethylene/norbornene (E/NB) copolymers are engineering plastics with high glass-transition temperature, excellent transparency, thermal stability, chemical resistance and high refractive indices which is advantageous for optical application. It is widely recognized that efficient catalysts based on well-defined transition metal complexes, able to precisely control the olefin copolymerization, should play an important role in the development of E/NB copolymers for target functions. Herein we report on the synthesis of the new vanadium(III) phosphine complex VCl3(PMePh2)2 (PMePh2 = methyldiphenylphosphine). The complex has been synthesized in high yield by reacting VCl3(THF)3 with 2.0 equiv of the ligand in toluene, and characterized by FTIR and X-ray structural analysis The reaction gave a V(III) complex with a trigonal bipyramidal geometry where the two phosphines are coordinated in the axial positions. The complex was first investigated as catalyst for the ethylene polymerization in the presence of Et2AlCl, exhibiting low activity (up to 156 kg PE/molV×h) to give a linear, high molecular weight poly(ethylene) with a number of methyl branches in the order of 13 per 1000 carbon atoms (Tm = 127 °C). The low activity was likely attributable to the deactivation of the active V(III) species to the inactive V(II) one, as suggested by the fact that addition of the oxidizing agent ethyltrichloroacetate (ETA) caused a significant increase in the activity up to 520 kgpol/molV×h. Furthermore, the (PMePh2)2VCl3/Et2AlCl/ETA catalytic system efficiently promoted the copolymerization of E with NB. The catalytic activity raised up to 4000 kgpol/molV×h. Mainly atactic copolymers with good comonomer incorporation (up to 45 mol% for [NB]/[E] = 4) were obtained and a strong tendency for comonomer alternation was observed.
Synthesis, X-Ray crystal structure and ethylene copolymerization behavior of the V(III) phosphine complex VCl3(PMePh2)2
Ivana Pierro;Giuseppe Leone;Giorgia Zanchin;Giovanni Ricci
2015
Abstract
Ethylene/norbornene (E/NB) copolymers are engineering plastics with high glass-transition temperature, excellent transparency, thermal stability, chemical resistance and high refractive indices which is advantageous for optical application. It is widely recognized that efficient catalysts based on well-defined transition metal complexes, able to precisely control the olefin copolymerization, should play an important role in the development of E/NB copolymers for target functions. Herein we report on the synthesis of the new vanadium(III) phosphine complex VCl3(PMePh2)2 (PMePh2 = methyldiphenylphosphine). The complex has been synthesized in high yield by reacting VCl3(THF)3 with 2.0 equiv of the ligand in toluene, and characterized by FTIR and X-ray structural analysis The reaction gave a V(III) complex with a trigonal bipyramidal geometry where the two phosphines are coordinated in the axial positions. The complex was first investigated as catalyst for the ethylene polymerization in the presence of Et2AlCl, exhibiting low activity (up to 156 kg PE/molV×h) to give a linear, high molecular weight poly(ethylene) with a number of methyl branches in the order of 13 per 1000 carbon atoms (Tm = 127 °C). The low activity was likely attributable to the deactivation of the active V(III) species to the inactive V(II) one, as suggested by the fact that addition of the oxidizing agent ethyltrichloroacetate (ETA) caused a significant increase in the activity up to 520 kgpol/molV×h. Furthermore, the (PMePh2)2VCl3/Et2AlCl/ETA catalytic system efficiently promoted the copolymerization of E with NB. The catalytic activity raised up to 4000 kgpol/molV×h. Mainly atactic copolymers with good comonomer incorporation (up to 45 mol% for [NB]/[E] = 4) were obtained and a strong tendency for comonomer alternation was observed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.