Brought to life more than half a century ago and successfully applied for high-value petrochemical intermediates production, nickel-catalyzed olefin oligomerization is still a very dynamic topic, with many fundamental questions to address and industrial challenges to overcome. The unique and versatile reactivity of nickel enables the oligomerization of ethylene, propylene and butenes into a wide range of oligomers that are highly sought-after in numerous fields to be controlled. Interestingly, both homogeneous and heterogeneous nickel catalysts have been scrutinized and employed to do this. This rare specificity encouraged us to interlink them in this review so as to open up opportunities for further catalyst development and innovation. An in-depth understanding of the reaction mechanisms in play is essential to being able to fine-tune the selectivity and achieve efficiency in the rational design of novel catalytic systems. This review thus provides a complete overview of the subject, compiling the main fundamental/industrial milestones and remaining challenges facing homogeneous/heterogeneous approaches as well as emerging catalytic concepts, with a focus on the last 10 years.

The ring-opening polymerization (ROP) of trimethylene carbonate (TMC) initiated by water or n-pentanol and catalyzed by trifluoromethanesulfonic acid (HOTf) or methanesulfonic acid (MSA) has been investigated. In contrast with HOTf, MSA was found to afford poly(trimethylene carbonate) (PTMC) free of ether linkages even under forcing conditions. The comparison of the two acids substantiates further that activity does not simply correlate with acidity. Analysis of the resulting PTMC by Size Exclusion Chromatography (SEC), 1 H NMR spectroscopy and mass spectrometry revealed the absence of molar mass control due to the formation of two polymer populations. This phenomenon was unambiguously attributed to the occurrence of two competitive mechanisms, namely Activated Monomer (AM) and Active Chain End (ACE). Such a situation is frequently encountered in the ROP of cyclic ethers, but is unprecedented for cyclic carbonates. Its deleterious impact on the polymerization control can be significantly reduced by maintaining the monomer concentration low enough so as to minimize the ACE mechanism. Accordingly, multifeed or continuous addition of the carbonate was shown to impart good control of molar mass and end-group fidelity.

No abstract