Intramolecular Formation of a Cr<sup>I</sup>(bis-arene) Species via TEA Activation of [Cr(CO)<sub>4</sub>(Ph<sub>2</sub>P(C<sub>3</sub>H<sub>6</sub>)PPh<sub>2</sub>)]<sup>+</sup>: An EPR and DFT Investigation
作者:Lucia McDyre、Emma Carter、Kingsley J. Cavell、Damien M. Murphy、James A. Platts、Katharine Sampford、Benjamin D. Ward、William F. Gabrielli、Martin J. Hanton、David M. Smith
DOI:10.1021/om2006062
日期:2011.9.12
catalytically relevant complex [Cr(CO)4(1)]+ (1 = Ph2P(C3H6)PPh2) by Et3Al (TEA) leads to formation of the Cr(I) bis-arene complex [Cr(1-bis-η6-arene)]+, as revealed by EPR and DFT calculations. This bis-arene complex is formed by intramolecular rearrangement and coordination of Cr(I) to the ligand phenyl groups in aliphatic solvents following loss of CO, preventing release of Cr(I) into solution. By comparison
Et 3 Al(TEA)对催化相关配合物[Cr(CO)4(1)] +(1 = Ph 2 P(C 3 H 6)PPh 2)的活化导致形成Cr(I)bis-芳烃络合物[CR(1 -双- η 6 -arene)] +,所揭示的EPR和DFT计算。这种双芳烃配合物是通过分子内的重排和在脂肪族溶剂中Cr(I)与脂族溶剂中的配体苯基配位而形成的,从而防止了Cr(I)释放到溶液中。通过在芳族溶剂(甲苯)中进行比较,[Cr(双甲苯基)] + 复合物优先形成。
Monitoring Structure and Valence State of Chromium Sites during Catalyst Formation and Ethylene Oligomerization by in Situ EPR Spectroscopy
作者:Angelika Brückner、Jabor K. Jabor、Ann E. C. McConnell、Paul B. Webb
DOI:10.1021/om800316m
日期:2008.8.1
complex were monitored by in situ EPR in cyclohexane and toluene, respectively, during oligomerization of ethylene. For Cr(acac)3/PNP, Cr3+ reduction is faster than low-spin Cr+ formation, suggesting that the major active species is EPR-silent, possibly an antiferromagnetic Cr+ dimer and/or Cr2+. Fast decomposition of [(PNP)CrCl2(μ-Cl)]2 to [Cr(η6-CH3C6H5)2]+ is a probable reason for low activity.