697
N
N
N
R
V
Cl
Cl
R
R
N
N
N
R
V
R
R
AlCl 3
N
N
N
R
V
Cl
ClAlCl 3
R
R
+
R = SiMe 3
AlMe 3
N
N
N
R
V
Me
Cl
R
R
Me 2 Al
few days
room temperature
N
N
N
R
V
Cl
R
R
Me 2 Al
N
N
N
R
V
Cl
R
R
AlMe 2
V(III)
V(II)
Cl
Cl
N
N
N
R
V
R
R
N
N
N
R
V
R
R
Cl
Cl
V
Cl
Cl
Scheme 12 The dinuclear V(III)-based complex and conversion to the V(II) species
O
S
S
V
O
O
Li(THF)2
Ar
Ar
O
S
S
V
OAr
N
O
S
S
V
Cl
[V(CH3CN)6]
Cl 2
V
O
O
V
O
MeCN
Cl
S
O
Cl
NCMe
S
S
HO
HO
V O
O
O
N
N
V Cl
O
O
N
N
NMe 2
O
NMe 2
OH
NMe 2
N
N
N
N
O
N
N
Ad
O
O
Ad
V
O
Cl
O
(a)
(b)
(c)
(d)
(e)
(f)
(g)
Ad: Adamantyl
O
N
N
S
OH
OH
Fig. 11 (a–g) Chelated V(III) complexes utilized for polymerization of olefin
Evolution of Ziegler-Natta Catalysts for Polymerization of Olefins