Time-Resolved Energy Dispersive EXAFS Measurement of Oligomerization Reaction Catalyzed by Nickel Homogeneous Catalyst on Addition of Triphenylphosphine and AlEt2(OEt) as Co-Catalyst

Abstract

Energy dispersive EXAFS (EDE) data have been analysed for the nickel
(3-diketonate catalysts. Ni( dpm)₂, using curved wave theory with ab initio
phase shifts. The derived parameters for metal compounds were in good
agreement, within experimental error of 0.02-0.05 Å for the bond distances.
Time-resolved EDE studies on Ni(dpm)₂ : PPh₃ : AlEt₂(OEt) : 1-hexene of
  1: 2 : 4 : 20 were acquired within 0.24 s for each spectrum. The growth
of a pre-edge feature and change at the top of the edge can be clearly seen
to show that the reaction reached completion in less than 6 s. A stopped
flow system was used for in situ time-resolved EDE studies on the nickel
systems at room temperature. EDE measurements using a new rectangular
Si(IlI) monochromator and Hamamatsu S4874 photodiode array at Station
9.3, Daresbury Laboratory have yielded consecutive spectral data taken at
1-1000 accumulations with 2-30 ms integration time to follow the changes
during initiation of the catalytic reaction.