Polymerisation neodymium catalyst

It is generally accepted that, in the polymerisation of dienes on lanthanide catalysts, the growing chain is attached to the transition metal by an 7t-allyl bond and that the chain growth occurs by incorporation of the monomer via the metal-carbon o-bond. In the case of neodymium catalysts, the delocalised 7t-allyl type structure of the terminal unit has been observed by spectroscopic methods [8, 26, 28, 58-60]. The results reported in these papers show that the relative contents of cis-l,A- and tri2ns-1,4-units in polydienes depend on the type of solvent used, the polymerisation temperature, structure of diene monomer, and the composition of lanthanide-based catalysts. These data can be interpreted in terms of the concept of isomerisation equilibrium between anti- and syn-forms of n-allyl terminal unit. One of the arguments in favour of the existence of this isomerisation... 

Figure 3.9 Stereospecific polymerisation of isoprene (2-methyl-butadiene-l,3). The Russian industry has implemented technologies of c/s-l,4-polyisoprene synthesis with Ti-Al Ziegler-Natta catalysts (synthetic c/s-isoprene rubber SKI-3) and neodymium salts-based lanthanide catalysts SKI-5 grade synthetic rubber (TU 2294-051-16810126-96). SKI-3 rubbers contain up to 93 1% of as-1,4 links, while their content in SKI-5 grade rubber is 96 1%...

---