873799-83-8Relevant articles and documents
Site-isolation effects in a dendritic nickel catalyst for the oligomerization of ethylene
Mueller, Christian,Ackerman, Lily J.,Reek, Joost N. H.,Kamer, Paul C. J.,Van Leeuwen, Piet W. N. M.
, p. 14960 - 14963 (2004)
Dendrimers, specifically suited to construct site-isolated groups due to their well-defined hyperbranched structure, have been used as a ligand design element for the construction of nickel catalysts for ethylene oligomerization. The dendritic P,O ligand indeed suppresses the formation of inactive bis-(P,O)Ni complexes in toluene, as is evident from NMR studies, and, as a consequence, outperforms the parent ligand in catalysis in this solvent. The dendritic effect observed in methanol is more subtle because both the dendritic ligand 1 and the parent 2 form bis(P,O)nickel complexes in solution according to NMR spectroscopy. Unlike the parent complex 8, the dendritic bis(P,O)Ni complex 7 derived from dendrimer ligand 1 is able to dissociate to a mono-ligated species under catalytic conditions, that is, 40 bar ethylene and 80 °C, which can enter the catalytic cycle. Indeed, dendritic ligand 1 gives much more active nickel catalysts for the oligomerization in methanol than does 2.
