The role of nitrogen-donor ligands in the palladium-catalyzed polyketones synthesis

Pd-Catalyzed Ring-Opening Polymerization of Cyclobutanols through C(sp3)-C(sp3) Bond Cleavage

A new approach to ring-opening polymerization (ROP) based on C(sp3)-C(sp3) bond cleavage is reported. This process is based on the ability of Pd to promote both the β-carbon elimination of a bifunctional cyclobutanol precursor and the C-C coupling process with the resulting Pd-alkyl intermediate. Consequently, novel polyketone materials are obtained. Owing to the modular synthesis of the used cyclobutanol monomers, the present ROP reaction allows the introduction of substitution patterns in the polymeric chain that are not accessible by current polyketone synthesis methodologies. We have explored in detail the initiation, propagation, and termination steps of this new polymerization process.

Recent Advances in Synthesis of Non-Alternating Polyketone Generated by Copolymerization of Carbon Monoxide and Ethylene

The copolymers of carbon monoxide (CO) and ethylene, namely aliphatic polyketones (PKs), have attracted considerable attention due to their unique property and degradation. Based on the arrangement of the ethylene and carbonyl groups in the polymer chain, PKs can be divided into perfect alternating and non-perfect alternating copolymers. Perfect alternating PKs have been previously reviewed, we herein focus on recent advances in the synthesis of PKs without a perfect alternating structure including non-perfect alternating PKs and PE with in-chain ketones. The chain structure of PKs, catalytic copolymerization mechanism, and non-alternating polymerization catalysts including phosphine-sulfonate Pd, diphosphazane monoxide (PNPO) Pd/Ni, and phosphinophenolate Ni catalysts are comprehensively summarized. This review aims to enlighten the design of ethylene/CO non-alternating polymerization catalysts for the development of new polyketone materials.

FeCl3-Promoted ring size-dictating diversity-oriented synthesis (DOS) of N-heterocycles using in situ-generated cyclic imines and enamines

The FeCl₃-promoted ring size-controlled oxidative activation of o-alkynylanilines opens up a complementary appealing protocol for poly-N-heterocycle synthesis.

Palladium alkyl complexes with a formazanate ligand: synthesis, structure and reactivity

The synthesis of formazanate palladium complexes is reported. Ligand-based redox-reactions and insertions of unsaturated substrates into the Pd–CH₃ bond are studied.

Palladium complexes with simple iminopyridines as catalysts for polyketone synthesis

A systematic study on iminopyridine palladium complexes demonstrates the relationship among NMR chemical shifts, ligand donor capability and catalytic performances.

Effect of chalcogens on CO insertion into the palladium-methyl bond of [(N^N^X)Pd(CH3)](+) (X = O, S, Se) and on CO/ethylene copolymerisation

Neutral chloromethylpalladium(II) complexes, [Pd(Cl)(CH3)(L)] (1a-5a) with ligands κ(2)-N^S-2-((3,5-di-tert-butyl-1H-pyrazol-1-yl)methyl)-6-(phenylthiomethyl)pyridine (L1), κ(2)-N^S-2-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-6-(phenylthiomethyl)pyridine (L2), κ(2)-N^Se-2-((3,5-di-tert-butyl-1H-pyrazol-1-yl)methyl)-6-(phenylselanylmethyl)pyridine (L3), κ(2)-N^Se-2-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-6-(phenylselanylmethyl)pyridine (L4), and κ(2)-N^N-2-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)-6-(phenoxymethyl)pyridine (L5) have been synthesised and characterised by various spectroscopic techniques. Ligands L1-L4 exhibit Npy^S/Se bidentate coordination whereas L5 shows an Npy^Npz bidentate coordination mode in their corresponding neutral palladium complexes. Abstraction of chloride in neutral palladium complexes with NaBAr4 (BAr4 = tetrakis[3,5-bis(trifluoromethyl)-phenyl]borate) resulted in the formation of the cationic palladium complexes 1b-5b, in which L1-L4 adopt a tridentate Npz^Npy^X (X = S or Se) coordination mode in their respective cationic palladium complexes (1b-4b) whilst L5 in complex 5b adopts a Npy^Npz bidentate coordination mode and the palladium centre is stabilized by the weakly coordinating acetonitrile. Compounds 1b-5b readily undergo CO insertion into the Pd-CH3 bond to form Pd-acyl that determines their ability to catalyse CO/ethylene copolymerisation to polyketones.

Carbonylation of ethene catalysed by Pd(II)-phosphine complexes

This review deals with olefin carbonylation catalysed by Pd(II)-phosphine complexes in protic solvents. In particular, the results obtained in the carbonylation with ethene are reviewed. After a short description of the basic concepts relevant to this catalysis, the review treats in greater details the influence of the bite angle, skeletal rigidity, electronic and steric bulk properties of the ligand on the formation of the products, which range from high molecular weight perfectly alternating polyketones to methyl propanoate. It is shown that the steric bulk plays a major role in directing the selectivity. Particular emphasis is given to the factors governing the very active and selective catalysis to methyl propanoate, including the mechanism of the catalytic cycles with diphosphine- and monophosphine-catalysts. A brief note on the synthesis of methyl propanoate using a “Lucite” type catalyst in ionic liquids is also illustrated. A chapter is dedicated to the carbonylation of olefins in aqueous reaction media. The nonalternating CO-ethene copolymerization is also treated.

Polymetallic complexes linked to a single-frame ligand: cooperative effects in catalysis

In an eco-friendly development, catalysis represents the key approach for converting raw materials into valuable products, particularly convenient for multi-step transformations. Mimicking Nature seems the smartest way to design poly-functional assemblies leading to the design of "synergic" catalysts. This perspective focuses on the advances in the conception of polymetallic catalysts bonded to a single ligand frame.