Catalyzed chain growth polymerisation of ethylene using lanthanidocenes/dialkylmagnesium: further developments and one pot synthesis of narrow dispersed high molecular weight fatty alcohols†
Ethylene polymerisation on dialkylmagnesium using neodymocene based catalysts via catalyzed chain growth (CCG) has been studied with the aim to improve the performance of the overall catalytic/transfer process. A one pot in situ alkylation procedure has been developed, using commonly available neodymium salts and substituted cyclopentadienes for the catalyst synthesis. This method has been shown to be as efficient as the use of the classical system involving the pre-synthesized well-defined as a precursor. Further experiments conducted on the classical system have also shown that despite their well-known coordination properties, introducing polyethers in the reaction resulted in a tremendous enhancement of the productivity (up to ×800), while keeping the dispersity of the resulting product as low as 1.1. This enhancement is assigned to the result of a much higher dissociation of dialkylmagnesiums, leading first to a strong increase of the exchange rate within the magnesium partners, in conjunction with a dissociative effect on the [Nd–Mg] associated complexes, providing a concomitant concentration increase of the putatively mononuclear species responsible for the propagation step. Application to the synthesis of higher molecular weight fatty alcohols of the UNILIN™ range via direct oxidation by diluted O2 (20% in Ar) of the (polyethylenyl)magnesiums has been performed, giving rise to overall yields of up to 92%, the latter being dependent on the targeted molecular weights.