were designed and synthesized for CO/styrene alternating copolymerization. Introduction of the rigid and bulky dibenzobarrelene backbone enhanced the thermal stability and the productivity of palladium catalyst. The dibenzobarrelene ligand backbone also improved the polymerizationcontrollability, and living CO/styrene copolymerizations were achieved at 15 °Cusing α-diimine palladium catalysts in CH2Cl2
Subtle Balance of Steric and Electronic Effects for the Synthesis of Atactic Polyketones Catalyzed by Pd Complexes with Meta-Substituted Aryl-BIAN Ligands
作者:Alessandro Scarel、M. Rosa Axet、Francesco Amoroso、Fabio Ragaini、Cornelis J. Elsevier、Alexandre Holuigue、Carla Carfagna、Luca Mosca、Barbara Milani
DOI:10.1021/om7011858
日期:2008.4.1
uinonediimine ligands, featured by substituents in meta-positions of the aryl rings, have been applied for the first time as ancillaryligands for the palladium-catalyzed CO/vinyl arene copolymerization. The nature and the number of substituents affect both the productivity and the molecular weight of the synthesized copolymers. Palladium complexes containing the nonsymmetric ligands are the most efficient
sulfoxide derivatives. The monocationic complexes are tested as precatalysts for the ethylene/methylacrylatecooligomerization under mild reaction conditions of temperature and ethylene pressure. The catalytic product is a mixture of ethylene/acrylate cooligomers and higher alkenes. The catalysts containing the newnonsymmetric ligand are found to be more productive than those with the symmetric Ar‐BIANs
that are direct precursors to augmented N-heterocycliccarbenes with a fixed cis geometry. Reduction of bis(imino)acenaphthene ligands with a LiAlH4/AlCl3 reagent mix initially produced the corresponding 1,2-diamines which, upon ring-closing reaction with triethyl orthoformate in acidic solution, gave the requisite ionic intermediates. Formation of the carbenes was then shown by preparation of selected