Stereospecific polymerization of 1,3-butadiene catalyzed by cobalt complexes bearing N-containing diphosphine PNP ligands
摘要:
A series of cobalt complexes bearing N-containing diphosphine PNP ligands has been synthesized and characterized. The nature of the ligand structure affects the binding of the ligand to the cobalt center and determines the coordination geometry of the cobalt complexes. All the complexes have been employed to catalyze the polymerization of 1,3-butadiene, in combination with methylaluminoxane (MAO) or ethylaluminum sesquichloride (EASC) as the cocatalyst. Both the nature of the ligand and the type of cocatalyst had a remarkable influence on the polymerization activity, microstructure and molecular weight of the resulting polymers. The [Co]/MAO catalytic systems resulted in relatively lower conversions of butadiene and cis-1,4 contents in the polymers than the corresponding [Co]/EASC catalytic systems. Upon activation with EASC, the polymerization behaviors of the catalytic systems were also affected by the reaction parameters. (C) 2012 Elsevier B.V. All rights reserved.
Additive‐Free Isomerization of Allylic Alcohols to Ketones with a Cobalt PNP Pincer Catalyst
作者:Brian Spiegelberg、Andrea Dell'Acqua、Tian Xia、Anke Spannenberg、Sergey Tin、Sandra Hinze、Johannes G. de Vries
DOI:10.1002/chem.201901148
日期:2019.6.12
Catalyticisomerization of allylic alcohols in ethanol as a green solvent was achieved by using air and moisture stable cobalt (II) complexes in the absence of any additives. Under mild conditions, the cobalt PNP pincer complex substituted with phenyl groups on the phosphorus atoms appeared to be the most active. High rates were obtained at 120 °C, even though the addition of one equivalent of base