Given that the pilot process required tens of kilograms of 2-acetyl-1,10phenanthroline, new alternative synthetic methodologies were developed, which
were scale-up synthetic procedures (Scheme 7). Driven by industrial
considerations, namely cheap substances for the pre-catalyst, fine chemical
companies are welcome to develop effective synthetic procedures and inform us;
therefore the detailed conditions are provided and we await further improvements.
One additional issue should also be addressed concerning iron and cobalt
complexes bearing bidentate ligands of 8-(benzimidazol-2-yl)quinolines (8A,
Scheme 8) [72], 8-iminoquinolines (8B, Scheme 8) [73], or 2-iminoquinolines
(8C, Scheme 8) [74]. These complexes also showed good catalytic activities
towards ethylene oligomerization or polymerization. Their complex pre-catalysts
show promising reactivity towards ethylene, though such bidentate ligands lack two
N
N
Fe
Cl
Ar
Cl
N
N
N
Fe
Cl
Ar
Cl
N
N
R
N
N
Fe
Cl
Ar
Cl
N
X
X = O, S
N
N
Fe
Cl
Ar
Cl
N
N
5A
5B
5C
5D
R = alkyl
Scheme 5 2-Nitrocyclic-6-iminopyridyliron complex pre-catalysts
N
N
M
Cl
Ar
R
Cl
N
R = H, Me, Et or Ph
N
M
Cl
Cl
N
R = H, Me, Et,
i
Pr or CH 2 Ph
N
N
R
N
M
Cl
Cl
N
R = H, Me or
t
Bu
N
O
R
M = Fe or Co
6A
6B
6C
Scheme 6 Iron and cobalt complexes bearing 1,10-phenanthroline derivatives
N
OH
NH 4 OH
NaHSO 4
N
NH 2
N
N
O
N
N
SeO 2
O
25 kg
23.5 kg
15 kg
4 kg
N
N
36%
N
N
C 6 H 5 CHO, Ac 2 O
31 kg
11 kg
50%
N
N
O 3 , DCM, MeOH
O
9 kg
90%
45%
25%
Scheme 7 Scaled-up synthetic procedures of 2-acetyl-1,10-phenanthroline
Novel Polyethylenes via Late Transition Metal Complex Pre-catalysts
171