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• 作者：Donagh Courtney^a ; C. John McAdam^b ; ^{mcadamj@alkali.otago.ac.nz} ; Anthony R. Manning^a ; Helge Mü ; ller-Bunz^a ; Yannick Ortin^a ; Jim Simpson^b
• 关键词：Cobalt ; Tetraphenylcyclobutadiene ; Ferrocenyl ; Alkyne ; Aldehyde reactions
• 刊名：Journal of Organometallic Chemistry
• 出版年：2012
• 期刊代码：64_0022328x
• 类别：ch
• 出版时间：15 May, 2012
• 卷：705
• 期：Complete
• 页码：7-22
• 文件大小：825 K

摘要

[Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄CC-CHO)], 4a, has been prepared from [Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄CHO)], 1a, by reactions similar to those used previously to convert [Fe(畏⁵-C₅H₅)(畏⁵-C₅H₄CHO)], 1b, to [Fe(畏⁵-C₅H₅)(畏⁵-C₅H₄CC-CHO)], 4b, i.e. via the dibromoethene [Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄CHCBr₂)], 2a, and alkyne [Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄CCH)], 3a. Both 4a and 4b undergo the normal aldehyde reactions with malononitrile and 2,4-dinitrophenylhydrazines to give their respective condensation products [Co(畏⁴-C₄Ph₄){畏⁵-C₅H₄CC-CHC(CN)₂}], 5a, and [Fe(畏⁵-C₅H₅){畏⁵-C₅H₄CC-CHC(CN)₂}], 5b; [Co(畏⁴-C₄Ph₄){畏⁵-C₅H₄CC-CHN-N(H)C₆H₃(NO₂)₂-2,4}], 6a, and [Fe(畏⁵-C₅H₅){畏⁵-C₅H₄CC-CHN-N(H)C₆H₃(NO₂)₂-2,4}], 6b, as separable mixtures of syn- and anti-isomers; and the anti-isomers of [Co(畏⁴-C₄Ph₄){畏⁵-C₅H₄CC-CHN-N(Me)C₆H₃(NO₂)₂-2,4}], 7a, and [Fe(畏⁵-C₅H₅){畏⁵-C₅H₄CC-CHN-N(Me)C₆H₃(NO₂)₂-2,4}], 7b. With [Fe₂(畏-C₅H₅)₂(CO)₂(渭-CO)(渭-CMe)][BF₄] 4a and 4b form blue-green [Fe₂(畏-C₅H₅)₂(CO)₂(渭-CO)(渭-C-CHCH-CC-C₅H₄-畏⁵)Co(畏⁴-C₄Ph₄)][BF₄], [8a][BF₄], and black [Fe₂(畏-C₅H₅)₂(CO)₂(渭-CO)(渭-C-CHCH-CC-C₅H₄-畏⁵)Fe(畏⁵-C₅H₅)][BF₄], [8b][BF₄] salts. 4a and 4b also react with the Wittig reagent [Fe(畏⁵-C₅H₅)(畏⁵-C₅H₄-CH₂PPh₃)][I]/ⁿBuLi to give mixtures of Z and E-[Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄-CC-CHCH-C₅H₄-畏⁵)Fe(畏⁵-C₅H₅)], 9a, and [Fe(畏⁵-C₅H₅)(畏⁵-C₅H₄-CC-CHCH-C₅H₄-畏⁵)Fe(畏⁵-C₅H₅)], 9b, which are separable for 9b but not 9a. The Wittig reagent obtained from [Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄-CH₂PPh₃)][Cl]/ⁿBuLi failed to react with 4a or 4b, but the reaction of 4a with [ClCH₂PPh₃][Cl]/^tBuOK gives very low yields of one expected product, E-[Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄-CC-CHCH-C₅H₄-畏⁵)Co(畏⁴-C₄Ph₄)], E-10a, together with a number of other unidentified compounds. The IR, ¹H NMR and ¹³C NMR, and UV/Vis spectra of 4-9 are reported, assigned and discussed. They confirm that 4-9 are Donor-蟺-Acceptor complexes in which Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄-) is a weaker donor than Fe(畏⁵-C₅H₅)(畏⁵-C₅H₄-), the acceptor strength increases for Acceptor 聽CHCHFc聽<聽CHN-N(R)C₆H₃(NO₂)₂-2,4聽<聽CHO聽<聽CHC(CN)₂聽<聽(-CHCH-C_渭⁺)(渭-CO)(CO)₂Fe₂(畏⁵-C₅H₅)₂, and that an ethyne linker, 蟺聽=聽CC, is less effective than an ethene linker, 蟺聽=聽CHCH, in promoting electronic communication between the Donor and Acceptor. The molecular structures of 2a, 3a, 4a, 4b, 5b, syn-6a, syn-6b (two crystal forms) and anti-7b have been determined by X-ray diffraction. They have normal molecular dimensions, and the C₅H₄-CC-CHY moiety does not deviate greatly from planarity with angles between the C₅H₄ and C-C(H)Y planes of 4.2-19.6掳. This contrasts with the structures of Fc-CC-R (R聽=聽aryl) complexes where the C₅H₄ and aryl planes are orthogonal or close to it. The electrochemistry of 3a/3b, 4a/4b, 5a/5b, syn-6a/6b, anti-7a/7b, E/Z-9a, Z-9b, E-9b and [Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄-CC-C₆H₅)] has been studied. The Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄-) complexes undergo reversible 1e oxidations at higher E掳 than their Fe(畏⁵-C₅H₅)(畏⁵-C₅H₄-) counterparts with E掳 increasing as the electron-withdrawing ability of the acceptor group increases. Furthermore, like their ferrocenyl counterparts, the alkyne derivatives [Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄-CC-X)] are oxidised at a more positive E掳 than the alkene complexes [Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄-CHCH-X)]. The UV/Visible spectrum of the oxidized species [Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄-CC-C₆H₅)]⁺ shows an absorption band at 960聽nm due to a C₆H₅聽鈫捖燙o(畏⁴-C₄Ph₄)(畏⁵-C₅H₄-) charge transfer transition; its equivalent in the spectrum of [Fe(畏⁵-C₅H₅)(畏⁵-C₅H₄-CC-C₆H₅)]⁺ is found at 797聽nm. This implies that {Co(畏⁴-C₄Ph₄)(畏⁵-C₅H₄-)}⁺ is a stronger acceptor than {Fe(畏⁵-C₅H₅)(畏⁵-C₅H₄-)}⁺.