826995-29-3Relevant academic research and scientific papers
2-Dialkyl- and 2-tert-butylphenylphosphinophenol(ate) nickel and palladium complexes: Control of E/Z-configuration in bis(P∩O --chelates) and activation of the nickel complexes for polymerization of ethylene
Heinicke, Joachim,Koehler, Martin,Peulecke, Normen,Keim, Wilhelm,Jones, Peter G.
, p. 1181 - 1190 (2008/10/09)
Nickel bis(2-dialkylphosphinophenolates), detected as the spent form of organonickel 2-dialkylphosphinophenolate catalysts for the polymerization of ethylene, were studied. In contrast to the impact of the P-basicity on the catalyst properties, the configuration of bis(2-dialkylphosphinophenolate) nickel is controlled only by steric effects. Small alkyl substituents favor, as do phenyl groups, square planar cis-bis(P∩O--chelates) while more bulky alkyl groups lead to trans-isomers. Dicyclohexyl- and tert-butylphenylphosphino groups give rise to borderline cases. Analogous palladium complexes show a slightly smaller effect of the metal size on the cis/trans-control. Intermediates on the way to PdII bis(P ∩O--chelates), trans-dichloro-bis(phosphinophenol)- and chlorophosphinophenol phosphinophenolate palladium(II) complexes could be isolated; the crystal structure of one of the latter was determined. The nickel bis(2-dialkylphosphinophenolates) can be activated as polymerization catalysts, to a limited extent by NiBr2·DME and sodium hydride or triethylsilane in THF, more efficiently by nBuLi or nBuLi/NiBr2·DME.
