Unusual Transformations of a Bipyridine Ligand in Attempts to Trap a Terminal Chromium(III) Alkylidene

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• 作者：Somying Leelasubcharoen ; Kin-Chung Lam ; Thomas E. Concolino ; Arnold L. Rheingold ; and Klaus H. Theopold
• 刊名：Organometallics
• 出版年：2001
• 出版时间：January 8, 2001
• 年：2001
• 卷：20
• 期：1
• 页码：182 - 187
• 全文大小：96K
• 年卷期：v.20,no.1(January 8, 2001)
• ISSN：1520-6041

文摘

Attempts to trap a terminal chromium alkylidene by reactions of dialkyl Cp*Cr(CH₂SiMe₃)₂(Cp* = es/gifchars/eta.gif" BORDER=0 >⁵-C₅Me₅) or metallacycle Cp*(THF)Cr(CH₂)₂SiMe₂ with the bidentate ligand 1,2-bis(dimethyphosphino)ethane (dmpe) lead to dinuclear paramagnetic chromium alkyls[Cp*Cr(CH₂SiMe₃)₂]₂(es/entities/mgr.gif">-es/gifchars/eta.gif" BORDER=0 >¹:es/gifchars/eta.gif" BORDER=0 >¹-dmpe) (1) and [Cp*Cr(CH₂)₂Si(CH₃)₂]₂(es/entities/mgr.gif">-es/gifchars/eta.gif" BORDER=0 >¹:es/gifchars/eta.gif" BORDER=0 >¹-dmpe) (2), respectively. On the other hand, the unusual mononuclear chromium complex (es/gifchars/eta.gif" BORDER=0 >⁵-pentamethylcyclopentadienyl)(2-(2' ',2' '-dimethyl-2' '-silapropyl)-1,2-dihydro[2,2']bipyridine-1,3' '-diyl)chromium(III) (3) was obtained by a reaction of Cp*(THF)Cr(CH₂)₂SiMe₂ with 1 equiv of2,2'-bipyridine (bipy). 3 is formed by carbon-carbon bond formation between one terminusof the metallacyle and the 2-position of the bipy ligand, at the expense of the aromaticity ofa pyridyl group. Single-electron oxidation of 3 with ferricenium hexafluorophosphate ([Cp₂Fe]PF₆) yielded 4, a dicationic dimer of 3 linked via a carbon-carbon bond between thebipy backbones. 1-4 were structurally characterized by X-ray diffraction.