Highly Active Ethene Polymerization Catalysts with Unusual Imine Ligands - Late Transition Metal Polymerization Catalysis - page 75

Tab. 3.1 1 H NMR shifts of diimine pyridine ligands 63 - 65 and iron complexes 66 , 67 , 69 in
CD 2 Cl 2 (relative to solvent at =5.25 ppm).

Imine sub. p-pyr m-pyr CMe m-Aryl o-Aryl p-Aryl

A: Ligands
Me 2 63a 7.90 8.50 2.25 7.05 2.04 6.93

iPr 2 65a 7.92 8.45 2.25 7.12 2.75, 1.13 7.12

Br 2 ,Me 64 7.93 8.51 2.33 7.39 2.31

Br 3 65 7.95 8.50 2.33 7.72

Cl 2 63 7.96 8.53 2.37 7.37 7.01

B: [N,N,N] Iron dichloride complexes
iPr 2 69 79.1 79.5 -36.3 14.6 -21.5/-5.5 -10.3

Br 2 ,Me 67 48.5 81.9 -28.7 18.0 24.2

Cl 2 66 42.8 81.0 -25.4 18.3 -11.1

3.2.2.2 N-Halogenoaryl-Containing Tridentate Ligands and their Fe Complexes
The synthesis of pyridine imines on the basis of 2,6-dichloro- ( 63 ), 2,6-dibromo-4-
methyl- ( 64 ) and 2,4,6-tribromoaniline ( 65 ) was successful through reaction of 2,6-
diacetylpyridine with the anilines in refluxing benzene and dynamically removing
the water formed. The condensation with the electron-poor anilines is not particu-
larly fast, but after two weeks enough product is present to allow their isolation
by column chromatography. Complexation of 63 - 65 to iron(II)chloride was
achieved in a fast and quantitative reaction by combining iron dichloride tetrahy-
drate with the ligands in butanol or THF. Reaction is fast and quantitative to give
the usual blue complexes (Tab. 3.1). In addition, diimine pyridine iron dichloride
complexes were prepared on the basis of 2,6-dimethyl ( 68 ) and 2,6-diisopropylani-
line ( 69 ). The proton chemical shifts of these paramagnetic compounds become
easily assignable by mutual comparison.

3.2.3
Salicylimine Systems

3.2.3.1 [N,O] Salicylimine Nickel Complexes Containing Peripheral N-Heteroaromatic
Substituents
Salicylaldimine ligands are in general synthesized by condensation of amines
with salicyl aldehydes. Quite similarly, using N-amino-azoles 9 - 19 as the amine
component affords under standard condensation conditions (alcoholic solvent,
protic catalysis, reflux) [N,O] ligands 70 - 85 in 15-90% yield. The yield is depen-
dent on the steric bulk of the substituted N-amino-N-heteroaromatic group. Two
series of ligands were synthesized, one with additional t -butyl substituents ( 78 - 85 )
to introduce more steric bulk in the ligand frame and those ( 70-77 ) without sub-
stituents on the salicyl backbone (Chart 3.6). All these ligands are stable, yellow
compounds which show spectroscopic properties consistent with their structure.