Quantification of the Steric Influence of Alkylphosphine–Sulfonate Ligands on Polymerization, Leading to High-Molecular-Weight Copolymers of Ethylene and Polar Monomers

A series
of palladium/​​alkylphosphine–​sulfonate
catalysts were synthesized and examined in the homopolymerization
of ethylene and the copolymerization of ethylene and polar monomers.
Catalysts with alkyl­phosphine–​sulfonate ligands
containing sterically demanding alkyl substituents afforded (co)­polymers
whose molecular weight was increased by up to 2 orders of magnitude
relative to polymers obtained from previously reported catalyst systems.
The polymer molecular weight was found to be closely correlated to
the Sterimol B5 parameter of the alkyl substituents in the alkyl­phosphine–​sulfonate
ligands. Thus, the use of bulky alkyl­phosphine–​sulfonate
ligands represents an effective and versatile method to prepare high-molecular-weight
copolymers of ethylene and various polar monomers, which are difficult
to obtain by previously reported methods.