Recent progress on the use of iron and cobalt complex precatalysts for ethylene reactivity is reviewed. The review is organized in terms of the denticity of the chelate ligands 10 employed, with particular reference to the influence of the ligand frameworks and their substituents on the catalytic performance for ethylene oligomerization/polymerization catalysis. The majority of the systems bear tri-dentate ligation at the iron/cobalt centre, though it is clear that bi-dentate 15 iron/cobalt complex pre-catalysts have also attracted significant attention. Such systems produce in most cases highly linear products ranging from oligomeric α-olefins to high molecular weight polyethylene, and as such are promising candidates for both academic and industrial 20 considerations.

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The catalyst systems LTiCl3/MAO (L = phenoxyimine ligand with a pendant aryl-O-CH3 donor arm) display exceptionally high activity in selective ethylene trimerization. By means of NMR and EPR spectroscopy, the nature of the Ti species formed in the catalyst systems LTiCl3/MAO, LTiCl3/MMAO and LTiCl3/AlR3/[Ph3C] + [B(C6F5)4] − (R = Me, Et, i Bu) has been studied. It was shown that outer-sphere ion pairs of the type [LTi IV Me2] + [A] − ([A] − = [MeMAO] − , [MeMMAO] − , or [B(C6F5)4] − ) are formed at the initial stage of the interaction of the catalyst LTiCl3 with MAO, MMAO and AlMe3/[Ph3C] + [B(C6F5)4] − . These ion pairs further partially convert into Ti III and Ti II species. In the systems LTiCl3/MAO and LTiCl3/AlMe3/[Ph3C] + [B(C6F5)4] − , complexes with proposed structures LTi III Me2, LTi II Cl and [LTi II (S)] + [A] − ([A] − = [MeMAO] − or [B(C6F5)4)] − , S = solvent or vacancy) were observed (concentration of Ti III species was lower than that of Ti II congeners). In contrast, in the system LTiCl3/MMAO, concentration of Ti III species (ion pairs of the 1 type [LTi III (µ-H)(µ-Cl)Al i Bu2] + [MeMMAO] − ) was higher than that of the Ti II counterparts (ion pairs [LTi II (S)] + [MeMMAO] − ). The system LTiCl3/MMAO displays lower selectivity in ethylene trimerization, compared to LTiCl3/MAO, due to undesirable PE formation. Probably, the ion pairs of Ti II participate in ethylene trimerization.

The first application of binaphthyl-stabilized palladium nanoparticles (Bin-PdNPs) with chiral modifiers in asymmetric hydrogenation of N-heteroaromatics is revealed.

A visible-light photoredox cleavage of α-allenylic C-O bond and alkenyl C-S formation is disclosed for the first time. The thiolation of allenyl phosphine oxides with diaryl disulfides occurs smoothly in metal-free and mild conditions, affording novel S,P-bifunctionalized butadienes with moderate to excellent yields. Mechanistic studies explain the cleavage of a C(sp)-O(Ar) bond in initiating a key alkenyl radical intermediate.

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