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Natcharee Kongprakaiwoot 《Journal of organometallic chemistry》2004,689(21):3350-3356
Reactions of 1,4-dibromo-2,5-difluorobenzene with two equivalents of lithium diisopropylamide at low temperature (T < −90 °C) followed by a quench with a slight excess of ClPPh2 afford 1,4-dibromo-2,5-bis(diphenylphosphino)-3,6-difluorobenzene (1) in good yields. Reacting 1 with two equivalents of BuLi followed by a quench with a slight excess of ClPR2 yield novel 1,2,4,5-tetrakis(phosphino)-3,6-difluorobenzenes 1,4-(PPh2)2-2,5-(PR2)2-C6F2 (R = Ph (2a); R = iPr (2b); R = Et (2c)) in moderate yields. Compounds 1 and 2a-c were characterized by multinuclear NMR spectroscopy and elemental analyses. In addition, molecular structures of 2a-c have been determined by single crystal X-ray crystallography. Phosphorus atoms of PPh2/PR2 substituents in 2a-c are displaced from the plane of the central phenyl ring due to steric interactions with neighboring groups. 相似文献
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Louis R. Pignotti Natcharee Kongprakaiwoot William W. Brennessel Jonas Baltrusaitis Rudy L. Luck Eugenijus Urnezius 《Journal of organometallic chemistry》2008,693(20):3263-3272
Reactions of 1,4-difluoro-2,5-dimethoxybenzene with LDA (1:2) at low temperatures generated organodilithio intermediates; quenching the reaction mixtures with chlorophosphines ClPR2 produced 1,4-bis(phosphino)-2,5-difluoro-3,6-dimethoxybenzenes 1a (R = Ph) and 1b (R = iPr). Demethylation of 1a–b was accomplished by BBr3, yielding bis(phosphino)hydroquinones 2a–b. Treating 2a–b with excess hydrogen peroxide produced bis(phosphinyl)hydroquinones 3a–b. The binucleating properties of 2a were established by the formation of a bimetallic nickel complex upon reaction with Ph2Ni(PMe3)2. Electrochemical activity of hydroquinones 2a–b and 3a–b was examined by cyclic voltammetry. In addition, compounds 2a, 3a and 3b were obtained in crystalline form and characterized by single-crystal X-ray diffraction. The influence of the fluorine substituents on the composition of the frontier orbitals of 2a and 3a was examined by computational methods. 相似文献
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Natcharee Kongprakaiwoot 《Journal of organometallic chemistry》2006,691(23):5024-5029
Double deprotonations of 1,4-dibromo-2,5-difluorobenzene with LDA (2 equiv., T < −90 °C) generate a reasonably stable organodilithium intermediate. Quenching this reaction mixture with chlorophosphines ClPR2 produce p-bis(phosphino)benzenes R2P-C6Br2F2-PR2 (R = Ph, 4a; R = iPr, 4b). Facile lithium-bromine exchange occurs upon exposure of 4a to BuLi (2 equiv., −80 °C), leading to the generation of another organodilithium intermediate. Addition of MeS-SMe (2 equiv.) to such reaction mixtures gives 1,4-bis(diphenylphosphino)-2,5-difluoro-3,6-bis(methylthio)benzene (2). Compound 2 is the first example of a neutral binucleating ligand featuring the [P,S] chelating sites on the opposite sides of a single phenyl ring. Compound 4b does not undergo the analogous transformation when subjected to the same conditions (2BuLi/2MeS-SMe). Addition of 2 to Fe(CO)5/2(Me3NO · 2H2O) reaction mixtures led to the isolation of the bimetallic complex {(CO)3Fe[P,S]-C6F2-[P,S]Fe(CO)3} (3), ([P,S] represents the chelating pockets formed by adjacent -PPh2 and -SMe groups). All of the new compounds were characterized by spectroscopic and analytical techniques (multinuclear NMR, mass-spectrometry, and/or elemental analysis). In addition, compounds 2 and 3 were characterized via single crystal X-ray diffraction methods. 相似文献
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