Highly stereoselective coordination polymerization of β‐myrcene from a lanthanide‐based catalyst: Access to bio‐sourced elastomers

Polymerization of β‐myrcene with neodymium borohydride‐based coordination catalysts is very efficient, affording poly‐β‐myrcene (polymyrcene, PMy) with high selectivity. With stoichiometric amounts of n ‐butylethyl magnesium (BEM) as co‐catalyst, good control over macromolecular data along with cis ‐stereoselectivity up to 98.5%, are obtained. In the presence of excess BEM, high level of transfer reactions efficiency between neodymium and magnesium is clearly evidenced whereas the selectivity switches to 3,4‐rich. Combining the neodymium pre‐catalyst with triisobutyl aluminum in the presence of a boron activator affords PMy in good yield, but the polymer material displays low solubility, likely due to the occurrence of crosslinking.