699
Among several complexes studied, the complex based on O,N chelate exhibited
high activity (642 kg polymer/mol V h) towards ethylene polymerization in presence of Et 2 AlCl (Fig. 12d) [59]. However, conversion of the V=O group in the complex to V=N-Ph-Me compromised the activity of the system. Amidinate-based V(V)
Cl 2 complexes were studied for copolymerization of propylene and 1,3-butadiene
(Fig. 12e). The polymerization was effective at −60 °C and produced syndiotacticrich polymer in presence of Et 2 AlCl co-catalyst and atactic polymer in presence of
methylaluminoxane co-catalyst [60]. An oxovanadium complex based on O,S,S,O
chelation exhibited high activity for ethylene polymerization (Fig. 12f) [61]. Similar
studies supported that aromatic-O- and aromatic-N-based ligands stabilized the
vanadium-based complexes in presence of Al-based co-catalyst. VO(OR 3 ) complexes based on tetradentate ligands possessing phenolic moieties exhibited
extremely high activity (96,500 kg polymer/(mol h bar) towards ethylene polymerization to produce polyethylene with very high molecular weight
(M w = 5.18–8.67 × 10
6
g/mol) (Fig. 13a). A dimeric complex of [VO(OR 3 )] 2 type
also displayed high activity (123,000 kg of polymer/mol h bar) for ethylene polymerization in presence of Me 2 AlCl and Cl 3 CCO 2 Et at 80 °C (Fig. 13b). Oxo complexes based on calyx-[3]arenes were synthesized from the vanadium alkoxide
precursors (Fig. 13c).
The resulting catalysts produced polyethylenes of very high molecular weight
under ambient temperature conditions [62]. Vanadium(V) complexes possessing a
combination of arylimido and aryloxo ligands were synthesized and utilized for
polymerization of ethylene in presence of methylaluminoxane as the co-catalyst by
V
N
O
O
O
O
V
O
O
O
V
O
O
O
O
O
(a)
(b)
N
O
V
Cl
Cl
N
O
V
Cl
Cl
N
O
V
Cl
Cl
(d)
(e)
(f)
O
O
O
O
O
O
V
O
O
O
O
O
O
O
V
O
(C)
Fig. 13 (a–f) The range of catalysts based on vanadium(V) for polymerization of ethylene and
copolymerization of olefins
Evolution of Ziegler-Natta Catalysts for Polymerization of Olefins
Among several complexes studied, the complex based on O,N chelate exhibited
high activity (642 kg polymer/mol V h) towards ethylene polymerization in presence of Et 2 AlCl (Fig. 12d) [59]. However, conversion of the V=O group in the complex to V=N-Ph-Me compromised the activity of the system. Amidinate-based V(V)
Cl 2 complexes were studied for copolymerization of propylene and 1,3-butadiene
(Fig. 12e). The polymerization was effective at −60 °C and produced syndiotacticrich polymer in presence of Et 2 AlCl co-catalyst and atactic polymer in presence of
methylaluminoxane co-catalyst [60]. An oxovanadium complex based on O,S,S,O
chelation exhibited high activity for ethylene polymerization (Fig. 12f) [61]. Similar
studies supported that aromatic-O- and aromatic-N-based ligands stabilized the
vanadium-based complexes in presence of Al-based co-catalyst. VO(OR 3 ) complexes based on tetradentate ligands possessing phenolic moieties exhibited
extremely high activity (96,500 kg polymer/(mol h bar) towards ethylene polymerization to produce polyethylene with very high molecular weight
(M w = 5.18–8.67 × 10
6
g/mol) (Fig. 13a). A dimeric complex of [VO(OR 3 )] 2 type
also displayed high activity (123,000 kg of polymer/mol h bar) for ethylene polymerization in presence of Me 2 AlCl and Cl 3 CCO 2 Et at 80 °C (Fig. 13b). Oxo complexes based on calyx-[3]arenes were synthesized from the vanadium alkoxide
precursors (Fig. 13c).
The resulting catalysts produced polyethylenes of very high molecular weight
under ambient temperature conditions [62]. Vanadium(V) complexes possessing a
combination of arylimido and aryloxo ligands were synthesized and utilized for
polymerization of ethylene in presence of methylaluminoxane as the co-catalyst by
V
N
O
O
O
O
V
O
O
O
V
O
O
O
O
O
(a)
(b)
N
O
V
Cl
Cl
N
O
V
Cl
Cl
N
O
V
Cl
Cl
(d)
(e)
(f)
O
O
O
O
O
O
V
O
O
O
O
O
O
O
V
O
(C)
Fig. 13 (a–f) The range of catalysts based on vanadium(V) for polymerization of ethylene and
copolymerization of olefins
Evolution of Ziegler-Natta Catalysts for Polymerization of Olefins