Copolymerization of Carbon Monoxide with Alkenes - Late Transition Metal Polymerization Catalysis - page 285

Scheme 8.10 Nickel-based catalyst precursors for the carbon monoxide-ethene copolymeriza-
tion.

8.5
Copolymerization of 1-Olefins

When 1-olefins are used as the substrate for the copolymerization with carbon
monoxide, different moieties can form due to the absence of symmetry elements
relating to the two unsaturated carbon atoms and to the enantiofaces of the olefin
substrate (four different insertion pathways) (Scheme 8.11) [29].
Accordingly, six different dyads can form, namely the head-to-head, head-to-tail,
and tail-to-tail, each one with either an l- or u -relative absolute configuration [78].
The regiochemistry of the copolymers of aliphatic 1-olefins is easily identified by
13 C NMR in the region of the resonances of the carbonyl groups [29]. In the case
of copolymers of styrene, both the regioregular (h-t) and irregular structures are
accessible; all the limiting stereochemical structures (iso-, syndio-, and atactic) are
known for the former. The syndiotactic structure is still missing for the corre-
sponding aliphatic olefins. In the following discussion, aromatic (styrene) and ali-
phatic (mostly propene) olefins will be separately treated due to the different type
of ligand used.

8.5.1
Copolymerization of Styrene (and Homologues)

The catalytic systems first disclosed in the patent literature for the copolymeriza-
tion of styrene [4], namely those modified with 2,2

-bipyridine 51 (Scheme 8.12)