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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
Author(s) -
Heinicke Joachim,
Köhler Martin,
Peulecke Normen,
Keim Wilhelm,
Jones Peter G.
Publication year - 2004
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200400003
Subject(s) - nickel , palladium , chemistry , steric effects , catalysis , chelation , medicinal chemistry , alkyl , ethylene , metal , polymer chemistry , inorganic chemistry , stereochemistry , organic chemistry
Abstract 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 Pd II bis(P∩O — ‐chelates), trans ‐dichloro‐bis(phosphinophenol)‐ and chloro‐phosphinophenol 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 NiBr 2 ·DME and sodium hydride or triethylsilane in THF, more efficiently by n BuLi or n BuLi / NiBr 2 ·DME.