Vinylic polymerization by homogeneous chromium(III) catalysts

Abstract

SUMMARY A new class of homogeneous chromium(II1)-based catalysts of the type [Cp*CrMeC1]2/MAO with different kinds of Cp ligands has been synthesized. The influence of the electronic nature and the sterical demand of the catalysts were explored with regard to the vinylic polymerization of norbornene. The catalyst activity could be increased by intensifying the electron-donating character of the Cp ligand, whereas the sterical demand of the Cp ligand affects the crystallinity of the obtained polynorbornene. In order to improve their processability, copolymers of norbornene with ethene were made using the [Cp*CrMeCl]JMAO catalyst, which led to copolymers with a high a-olefin content. Furthermore, highly linear, ultra-high molecular weight polyethylene was obtained using the new class of chromium(II1)-based catalysts.

Co(II)-catalyzed polymerization of bicyclo[2.2.1]hept-2-ene in the presence of ethene

“…In contrast, Cr/ MAO systems in toluene have a higher activity than Cr/ MAO* systems in chlorobenzene [20]. We conclude from these results that the active Co center is more polar than the corresponding Cr species.…”

Vinyl polymerization of norbornene with bis(imino)pyridyl nickel(II) complexes

“…The reaction temperature also considerably affects the catalytic activities and molecular weight (Table VII). With increasing reaction temperature to 30 C, the catalytic activity reached the highest value at 4.7 Â 10 6 g PNB/(mol Ni h). When the temperature further increased, the activity remained constant value, indicating that the activity center was stable in temperature range of C. However, the molecular weight of PNB increased to 3.5 Â 10 5 g/mol at 30 C, it is then drastically decreased to 0.41 Â 10 Table VIII.…”

“…The dihedral angles between the phenyl rings and the plane formed by three coordinated nitrogen atoms are 79.20(37) and 79.21 (26) , respectively. The dihedral angle of the two phenyl rings is 79.30 (30) . The Cl1 and Cl2 atoms deviate from the plane formed by three nitrogen atoms by 0.0312 and 0.6036 Å , respectively.…”

“…[9][10][11] So far, the NB vinyl polymerization has been widely attracted to study. 5 In recent years, the vinyl-type polynorbornene (PNB) can be prepared by nickel, [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] cobalt, [27][28][29] chromium, 30,31 titanium, 7,32,33 zirconium, 34 iron, 35,36 palladium, [37][38][39][40][41][42][43][44][45][46][47][48][49] and copper 21,22,24,50 complexes activated with methylaluminoxane (MAO) or cationic complexes with weakly coordinating counter ions like BF À 4 or PF À 6 (Ni, Pd). Since the late 1990s, one of the latest breakthroughs in the olefin polymerization field has been the discovery of the neutral salicylaldiminato nickel complexes …”

Synthesis and characterization of novel neutral nickel complexes bearing fluorinated salicylaldiminato ligands and their catalytic behavior for vinylic polymerization of norbornene

“…[1] The coordination polymerization of norbornene yields 2,3-connected, rotationally strongly constrained vinyl-type polynorbornene, which results in unique physical properties, such as high chemical resistance, good UV resistance, low dielectric constant, high glass transition temperature, excellent transparency, high refractive index, and low birefringence. [2,3] Vinyl-type polynorbornenes can be prepared by transition metal catalysts based on nickel, [4 -15] chromium, [16,17] titanium, [18,19] zirconium, [20,21] cobalt, [17,22,23] palladium [24 -33] and copper complexes. [34,35] Zirconocenes and cationic palladium complexes are two important types of catalysts for vinylic polymerization of norbornene.…”