Studies of Ligand and Solvent Effects in the Alternating Copolymerization of Carbon Monoxide and Ethene by Palladium-Diphosphine Catalysis

Homo- and heterometallic chiral dynamic architectures from allyl-palladium(II) building blocks

New chiral tetranuclear square-like homo- and heterometallamacrocycles containing allyl-palladium and either {Pd(P-P)*} or {Pt(P-P)*} optically pure moieties (P-P* = (2S,3S)-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphanyl)butane ((S,S)-DIOP) and (2S,4S)-2,4-bis(diphenylphosphanyl)pentane ((S,S)-BDPP)) have been obtained by the self-assembly of [Pd(η³-2-Me-C₃H₄)(4-PPh₂py)₂]⁺ and [M(P-P)*(H₂O)₂]²⁺ building blocks in a 1 : 1 molar ratio. The supramolecular assemblies thus prepared [{Pd(η³-2-Me-C₃H₄)}₂(4-PPh₂py)₄{M(P-P)*}₂](CF₃SO₃)₆ (M = Pd, Pt) have been fully characterised by multinuclear NMR spectroscopy and MS spectrometry. The structures display remarkable differences on their dynamic behaviour in solution that depend on the lability and thermodynamic strength of M-py bonds. The structural characteristics of the new metallamacrocyles obtained have also been unambiguously established by XRD analysis. The architectures have been assayed as catalytic precursors in the asymmetric allylic alkylation reaction.

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.