C-Substituted Bis(diphenylphosphino)methane-Type Ligands for Chromium-Catalyzed Selective Ethylene Oligomerization Reactions

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• 作者：Arminderjit Dulai ; Henritte de Bod ; Martin J. Hanton ; David M. Smith ; Stephen Downing ; Stephen M. Mansell ; Duncan F. Wass
• 刊名：Organometallics
• 出版年：2009
• 出版时间：August 10, 2009
• 年：2009
• 卷：28
• 期：15
• 页码：4613-4616
• 全文大小：694K
• 年卷期：v.28,no.15(August 10, 2009)
• ISSN：1520-6041

文摘

Ligand backbone alkylation of the complex [Cr(CO)₄(dppm)] (dppm = bis(diphenylphosphino)methane) with alkyl iodides yields the C-substituted dppm ligand complexes [Cr(CO)₄{Ph₂PCH(R)PPh₂}] (R = methyl, n-hexyl, benzyl). Activation of these complexes via one-electron oxidation with Ag[(Al(OC₄F₉)₄] and CO removal with triethylaluminium, or (in the case of R = methyl) by in situ treatment of the free ligand with a chromium salt and modified methyl alumoxane (MMAO), leads to catalysts showing some selectivity for ethylene trimerization and tetramerization. NMR spectroscopic studies of the parent dppm or [Cr(CO)₄(dppm)] compounds suggest that ligand deprotonation and decomplexation may be the cause of the surprisingly poor catalytic performance of these specific derivatives.