- Determination of hydrophobicity scale of tetraphenylborate and its derivatives by ferrocene based three-phase electrodes
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In three-phase electrodes (TPE), ferrocene (Fc) was often thought to be useless for ion transfer injection because its oxidized form has very low affinity for organic phase. Instead, lipophilic decamethylferrocene (DMFc) was employed as a better probe for the ion transfer study. However, our present results indicate that the commonly-used DMFc based TPE was not applicable for the transfer of strong hydrophobic tetraphenylborate and its derivatives (TPBs); whereas the developed Fc based TPE can meet this special requirement. Taking this advantage, we firstly evaluate the standard ion transfer energies of these TPBs and get a full knowledge of their hydrophobicity scale, which will benefit the related areas such as hydrophobic ionic liquids and lipophilic anion exchangers.
- Hu, Keke,Xu, Bing,Shao, Huibo
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- Synthesis, Structure, and Reactivity of the Ethyl Yttrium Metallocene, (C5Me5)2Y(CH2CH3), Including Activation of Methane
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(C5Me5)2Y(μ-Ph)2BPh2, 1, reacted with ethyllithium at -15°C to make (C5Me5)2Y(CH2CH3), 2, which is thermally unstable at room temperature and formed the C-H bond activation product, (C5Me5)2Y(μ-H)(μ-n1:n5-CH2C5Me4)Y(C5Me5), 3, containing a metalated (C5Me5)1- ligand. Spectroscopic evidence for 2 was obtained at low temperature, and trapping experiments with iPrNCNiPr and CO2 gave the Y-CH2CH3 insertion products, (C5Me5)2Y[iPrNC(Et)NiPr-k2N,N′], 4, and [(C5Me5)2Y(μ-O2CEt)]2, 5. Although 2 is highly reactive, low temperature isolation methods allowed the isolation of single crystals which revealed an 82.6(2)°Y-CH2-CH3 bond angle consistent with an agostic structure in the solid state. Complex 2 reacted with benzene and toluene to make (C5Me5)2YPh, 7, and (C5Me5)2YCH2Ph, 8, respectively. The reaction of 2 with [(C5Me5)2YCl]2 formed (C5Me5)2Y(μ-Cl)(μ-n1:n5-CH2C5Me4)Y(C5Me5) in which a (C5Me5)1- ligand was metalated. C-H bond activation also occurred with methane which reacted with 2 to make [(C5Me5)2YMe]2, 9.
- MacDonald, Matthew R.,Langeslay, Ryan R.,Ziller, Joseph W.,Evans, William J.
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- Reductions of aliphatic and aromatic nitriles to primary amines with diisopropylaminoborane
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Diisopropylaminoborane [BH2Nf)Pr)2] in the presence of a catalytic amount of lithium borohydride (LiBH4) reduces a large variety of aliphatic and aromatic nitriles in excellent yields. BH 2NOPr)2 can be prepared by two methods: first by reacting diisopropylamineborane [(iPr)2N)BH3] with 1.1 equiv of n-butylhthium (n-BuLi) followed by methyl iodide (MeI), or reacting iPrN:BH 3 with 1 equiv of n-BuLi followed by trimethylsilyl chloride (TMSCl). BH2N(ZPr)2 prepared with MeI was found to reduce benzonitriles to the corresponding benzylamines at ambient temperatures, whereas diisopropylaminoborane prepared with TMSCl does not reduce nitriles unless a catalytic amount of a lithium ion source, such as LiBH4 or lithium tetraphenylborate (LiBPh4), is added to the reaction. The reductions of benzonitriles with one or more electron-withdrawing groups on the aromatic ring generally occur much faster with higher yields. For example, 2,4-dichlorobenzonitrile was successfully reduced to 2,4-dichlorobenzylamine in 99% yield after 5 h at 25 °C. On the other hand, benzonitriles containing electron-donating groups on the aromatic ring require refluxing in tetrahydrofuran (THF) for complete reduction. For instance, 4- methoxybenzonitrile was successfully reduced to 4-methoxybenzylamine in 80% yield. Aliphatic nitriles can also be reduced by the BH2N(iPr) 2/cat. LiBH4 reducing system. Benzyl cyanide was reduced to phenethylamine in 83% yield. BH2NOPr)2 can also reduce nitriles in the presence of unconjugated alkenes and alkynes such as the reduction of 2-hexynenitrile to hex-5-yn-l-amine in 80% yield. Unfortunately, selective reduction of a nitrile in the presence of an aldehyde is not possible as aldehydes are reduced along with the nitrile. However, selective reduction of the nitrile group at 25 °C in the presence of an ester is possible as long as the nitrile group is activated by an electron-withdrawing substituent. It should be pointed out that lithium aminoborohydrides (LABs) do not reduce nitriles under ambient conditions and behave as bases with aliphatic nitriles as well as nitriles containing acidic a-protons. Consequently, both LABs and BH2NOPr)2 are complementary to each other and offer methods for the selective reductions of multifunctional compounds.
- Haddenham, Dustin,Pasumansky, Lubov,DeSoto, Jamie,Eagon, Scott,Singaram, Bakthan
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supporting information; experimental part
p. 1964 - 1970
(2009/07/01)
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- Electron Transfer and Ion Pairing, 7. Contact Ion Pairs of Sulfur-Containing Radical Anions
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The structurally different radical anions M(-) of peralkylated 1-sila-2,5-diazacyclopentane-3,4-dithione and of tetrakis(isopropylthio)-p-benzoquinone are generated by reduction with potassium/2.2.2-cryptand under aprotic conditions in THF solution.On addition of Li(+)B(C6H5)4(-), both form hitherto elusive sulfur-containing contact ion pairs, which are characterized by their ESR/ENDOR spectra. - Keywords: Contact Ion Pairs, ESR, ENDOR and Triple Spectra, Reduction of 1-Sila-2,5-diazacyclopentane-3,4-dithione and of Tetrakis(isopropylthio)-p-benzoquinone
- Bock, Hans,Haenel, Peter,Herrmann, H.-F.,Dieck, Heindirk tom
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p. 1240 - 1246
(2007/10/02)
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