Highly Active and Thermally Robust Nickel Enolate Catalysts for the Synthesis of Ethylene-Acrylate Copolymers

The insertion copolymerization of polar olefins and ethylene remains a significant challenge in part due to catalysts' low activity and poor thermal stability. Herein we demonstrate a strategy toward addressing these obstacles through ligand design. Neutral nickel phosphine enolate catalysts with large phosphine substituents reaching the axial positions of Ni achieve activity of up to 7.7×10³  kg mol^-1  h^-1 (efficiency >35×10³  g copolymer/g Ni) at 110 °C, notable for ethylene/acrylate copolymerization. NMR analysis of resulting copolymers reveals highly linear microstructures with main-chain ester functionality. Structure-performance studies indicate a strong correlation between axial steric hindrance and catalyst performance.

Synthesis and Structural Characterisation of an N-Phosphanyl Ferrocene Carboxamide and its Ruthenium, Rhodium and Palladium Complexes

[((Diphenylphosphanyl)amino)carbonyl]ferrocene (1) has been synthesized and coordinated to light platinum metals, ruthenium, rhodium and palladium, in diverse coordination modes. Specifically, compound 1 was used to prepare the following phosphane complexes, [(η⁶ -mes)RuCl₂ (1-κP)], [(η⁵ -C₅ Me₅ )RhCl₂ (1-κP)], trans-[PdCl₂ (1-κP)₂ ], and [(L^NC )PdCl(1-κP)] (mes=mesitylene, L^NC =[2-(dimethylamino-κN)methyl]phenyl-κC¹ ). They were subsequently converted into cationic O,P-chelate complexes by halide abstraction with AgClO₄ and into neutral O,P-chelate complexes by deprotonation with potassium tert-butoxide. All coordination compounds and phosphane chalcogenides 1E (P-bound chalcogen atom E=O, S and Se), which were also synthesised, were structurally characterised using spectroscopic methods (IR, multinuclear NMR and ESI MS) and single-crystal X-ray diffraction analysis. The electrochemical behaviour of the prepared compounds was studied by cyclic voltammetry, and the (L^NC )Pd-1 complexes were further studied by Mössbauer spectroscopy.