Pincer Chromium(II) and Chromium(III) Complexes Supported by Bis(imino)aryl NCN ligands: Synthesis and Catalysis on Isoprene Polymerization

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• 作者：Zhizhou Liu ; Wei Gao ; Xiaoming Liu ; Xuyang Luo ; Dongmei Cui ; Ying Mu
• 刊名：Organometallics
• 出版年：2011
• 出版时间：February 28, 2011
• 年：2011
• 卷：30
• 期：4
• 页码：752-759
• 全文大小：1054K
• 年卷期：v.30,no.4(February 28, 2011)
• ISSN：1520-6041

文摘

Reactions of 2,6-(ArN鈺怌H)₂C₆H₃Li with CrCl₂(THF)₂ afford two trinuclear bis(imino)aryl NCN pincer Cr(II) complexes {[2,6-(ArN鈺怌H)₂C₆H₃]Cr(渭-Cl)₂}₂Cr [Ar = 2,6-Me₂C₆H₃ (1a), 2,6-Et₂C₆H₃ (1b)], and a mononuclear bis(imino)aryl NCN pincer Cr(II) complex [2,6-(ArN鈺怌H)₂C₆H₃]Cr(渭-Cl)₂Li(THF)₂ [Ar = 2,6-ⁱPr₂C₆H₃ (1c)], respectively. Similar reactions of 2,6-(ArN鈺怌H)₂C₆H₃Li with CrCl₃(THF)₃ produce only mononuclear bis(imino)aryl NCN pincer Cr(III) complexes [2,6-(ArN鈺怌H)₂C₆H₃]CrCl₂(THF) [Ar = 2,6-Me₂C₆H₃ (2a), 2,6-Et₂C₆H₃ (2b), 2,6-ⁱPr₂C₆H₃ (2c)]. X-ray crystallographic analysis reveals that the terminal Cr(II) atoms in 1a and 1b and the Cr(II) atom in 1c possess a distorted trigonal bipyramidal coordination environment with the C_ipso atom of the pincer ligand and two chloride atoms in the equator and the two imine nitrogen atoms in the apical positions, while the Cr(III) complexes 2a, 2b, and 2c all adopt a distorted octahedral geometry around the chromium metal. Upon activation with trialkylaluminum and [Ph₃C]⁺[B(C₆F₅)₄]^{鈭?/sup>, the Cr(III) complexes show high catalytic activity for isoprene polymerization and afford polyisoprene with predominately trans-1,4 units, whereas the Cr(II) complexes are inert under the same conditions.}