Synthesis of Arenethiolate Complexes of Divalent and Trivalent Lanthanides from Metallic Lanthanides and Diaryl Disulfides: Crystal Structures of [{Yb(hmpa)(3)}(2)(&mgr;-SPh)(3)][SPh] and Ln(SPh)(3)(hmpa)(3) (Ln = Sm, Yb; hmpa = Hexamethylphosphoric Triamide)

A convenient and one-pot synthetic method of lanthanide thiolate compounds was developed. An excess of metallic samarium, europium, and ytterbium directly reacted with diaryl disulfides in THF to give selectively Ln(II) thiolate complexes, [Ln(SAr)(&mgr;-SAr)(thf)(3)](2) (1, Ln = Sm; 2, Ln = Eu; Ar = 2,4,6-triisopropylphenyl), Yb(SAr)(2)(py)(4) (3, py = pyridine), and [{Ln(hmpa)(3)}(2)(&mgr;-SPh)(3)][SPh] (6, Ln = Sm; 7, Ln = Eu; 8, Ln = Yb; hmpa = hexamethylphosphoric triamide). Reaction of metallic lanthanides with 3 equiv of disulfides afforded Ln(III) thiolate complexes, Ln(SAr)(3)(py)(n)()(thf)(3)(-)(n)() (9a, Ln = Sm, n = 3; 9b, Ln = Sm, n = 2; 10, Ln = Yb, n = 3) and Ln(SPh)(3)(hmpa)(3) (11, Ln = Sm; 12, Ln = Eu; 13, Ln = Yb). Thus, Ln(II) and Ln(III) thiolate complexes were prepared from the same source by controlling the stoichiometry of the reactants. X-ray analysis of 8 revealed that 8 has the first ionic structure composed of triply bridged dinuclear cation and benezenethiolate anion [8, orthorhombic, space group P2(1)2(1)2(1) with a = 21.057(9), b = 25.963(7), c = 16.442(8) ?, V = 8988(5) ?(3), Z = 4, R = 0.040, R(w) = 0.039 for 5848 reflections with I > 3sigma(I) and 865 parameters]. The monomeric structures of 11 and 13 were revealed by X-ray crystallographic studies [11, triclinic, space group P&onemacr; with a = 14.719(3), b = 17.989(2), c = 11.344(2) ?, alpha = 97.91(1), beta = 110.30(2), gamma = 78.40(1) degrees, V = 2751.9(9) ?(3), Z = 2, R = 0.045, R(w) = 0.041 for 7111 reflections with I > 3sigma(I) and 536 parameters; 13, triclinic, space group P&onemacr; with a = 14.565(2), b = 17.961(2), c = 11.302(1) ?, alpha = 97.72(1), beta = 110.49(1), gamma = 78.37(1) degrees, V = 2706.0(7) ?(3), Z = 2, R = 0.031, R(w) = 0.035 for 9837 reflections with I > 3sigma(I) and 536 parameters]. A comparison with the reported mononuclear and dinuclear lanthanide thiolate complexes has been made to indicate that the Ln-S bonds weakened by the coordination of HMPA to lanthanide metals have ionic character.     

Synthesis and property of soluble poly(1,1′-dialkyl-3,3′-ferrocenylenevinylene)s via titanium-induced dicarbonyl-coupling reaction of 1,1′-dialkylferrocene-3,3′-dicarbaldehydes

1,1′-Dialkylferrocene-3,3′-dicarbaldehydes ( 1a–c ) with long alkyl chains such as ethyl, hexyl, and dodecyl groups were prepared in 13–25% yield via three-step reactions. The titanium-induced dicarbonyl-coupling reaction of 1a–c gave poly(1,1′-dialkyl-3,3′-ferrocenylenevi-nylene)s ( 2a–c ) in quantitative yields, which were the molecular weights of 3000–10,000 and highly soluble in chloroform, benzene, and hexane. The electrical conductivity and the third-order nonlinear optical susceptibility for poly(1,1′-dihexyl-3,3′-ferrocenylenevinylene) ( 2b ) were estimated to be 1 × 10^?2 S/cm on doping with iodine and 1–4 × 10^?12 esu at a wavelength of 1–2.4 μm, respectively. © 1995 John Wiley & Sons, Inc.     

Reaction of octafluorocyclopentene with various carbon nucleophiles

The treatment of octafluorocyclopentene with organolithium reagents gave the corresponding symmetrical disubstituted perfluorocyclopentenes in good to high yields. The reaction with Grignard reagents led to the monosubstituted perfluorocyclopentenes, which were subjected to the further nucleophilic substitution reaction using another Grignard or aryllithium reagents, unsymmetrical disubstituted perfluorocyclopentenes being obtained in high yields.     

Radical cyclization by ipso substitution of the methoxy group: considerable effect of HMPA on samarium-mediated cyclization

Alkyl radicals generated by treatment of thiocarbamates of conformationally favorable 3-alkyl-3-arylpropan-1-ols with tris(trimethylsilyl)silane and AIBN efficiently undergo intramolecular ipso substitution of the methoxy group, yielding the corresponding cyclized products. In contrast, either conformationally favorable or flexible 1-arylalkan-3- or 4-ones easily cyclize into five- or six-membered condensed rings by treatment with SmI(2) via ketyl radical intermediates. The addition of HMPA as cosolvent dramatically changes the cyclization mode of the SmI(2)-induced reaction, and the para-cyclization products are exclusively formed. This "HMPA effect" can be rationalized by the strong chelating ability of HMPA with the samarium atom.     

Electrochemical analysis of single nucleotide polymorphisms of p53 gene

Single nucleotide polymorphisms (SNPs) of cancer repression gene p53 were analyzed electrochemically with ferrocenyl naphthalene diimide (1) as a hybridization indicator. The SNPs studied were the transition to A from G in the codon for amino acid at positions 175, 248 or 273 and the transversion to C from G in the codon for the amino acid at position 72. Thus, 20-meric oligonucleotides carrying the SNP site were used both as a sample and a probe with the latter immobilized on an electrode. Even one base difference on the p53 gene resulted in a significant difference in the current response of 1 and the magnitude of the response correlated with the amount of the DNA hybrid on the electrode. Moreover, when PCR products of exon 4, on which the P72/R72 SNP resides, of the p53 gene were analyzed by this method, the heterozygote and homozygotes were discriminated with modest precision.     

Analytical investigation of two-step adsorption kinetics on surfaces

Analytical equations of two-step adsorption kinetics on surface have been derived. Moreover, computer simulations have been carried out to interpret various experimental adsorption kinetics previously reported. In the first case, molecules are further adsorbed from a solution onto a layer consisting of previously adsorbed molecules. This model was applied to the adsorption kinetics of hexadecyltrimethylammonium chloride (C16TAC) on a self-assembled monolayer (SAM) of 3-mercaptopropionic acid (T. Imae, H. Torii, J. Phys. Chem. B 104 (2000) 9218). The second case is that some of the initially adsorbed molecules are released from the adlayer with further time course. The adsorption of C16TAC on 1-dodecanethiol SAM (T. Imae, T. Takeshita, K. Yahagi, Stud. Surf. Sci. Catal. 132 (2001) 477) agrees with this mechanism. The strict mathematical developments presented in this work are demanded to specify the physical meaning of observed non-Langmuir adsorption kinetics, consisting of the two exponential terms.     

Determination of rare earth elements in geological samples by inductively-coupled plasma atomic emission spectrometry after oxalate coprecipitation and cation-exchange column separation

A method for separation and determination of traces of 14 rare earth elements (REEs) in geological samples is described. Determination by inductively-coupled plasma atomic emission spectrometry follows oxalate coprecipitation of the REEs with calcium as carrier and cation- exchange column separation in nitric acid. The combination of the two separation techniques improved the low recoveries found for Sm, Eu, and Gd when only ion-exchange was used, especially for iron- and aluminum-rich samples. The method was applied to the analysis of geological standard materials NBS SRM 688 (basalt), NBS SRM 278 (obsidian), GSJ JB-1 (basalt), GSJ JA- 2 (andesite), and CCRMP SY-3 (syenite). The results were evaluated on the basis of chondrite- normalized rare earth element distribution patterns.     

Wetting of surfactant solutions by alkanes.

Ellipsometry, surface tensiometry, and contact-angle measurement have been used to study the transition between partial wetting and pseudo-partial wetting of surfactant solutions by alkanes. In the partial wetting regime, the air-water surface tension is the same with and without alkane. In the pseudo-partial wetting regime, the air-water surface tension is lowered by the presence of alkane, showing that oil is solubilised into the surfactant monolayer. A discontinuous change in the coefficient of ellipticity with increasing surfactant concentration provides unequivocal evidence for the first-order nature of the wetting transitions. Ellipsometry has been used to explore the generality of wetting transitions of alkanes (dodecane, hexadecane, and squalane) on surfactant solutions [dodecyltrimethylammonium bromide, tetredecyltrimethylammonium bromide, dibucaine hydrochloride, and Aerosol OT (AOT)]. Of the systems studied, only hexadecane on AOT solutions did not show a wetting transition. Excess alkane remains as a lens on the surface of the surfactant solutions at all concentrations, but the contact angle is a minimum at the wetting transition. A semiquantitative model for the variation of the contact angle with surfactant concentration is provided.     

Loss of99Tc from seaweeds in the course of dry ashing

Loss of⁹⁹Tc in seaweed during dry ashing has been investigated. Two kinds of brown seaweeds labeled with⁹⁹Tc were ashed for 24 or 48 h at 400, 450 and 500 °C, showing no correlation between the loss of⁹⁹Tc and species, temperature and time of ashing. The averaged recovery of⁹⁹Tc was 91.0±4.0%, indicating that most of the⁹⁹Tc in the seaweed was retained within the matrix of the ash which was obtained under general conditions of ashing.     

Construction of the benzylic quaternary carbon center of zoanthenol by intramolecular Mizoroki-Heck reaction of enone

[reaction: see text]. Stereocontrolled synthesis of the ABC ring framework of zoanthenol has been achieved. Our studies show that a beta,beta-disubstituted enone can act as a good acceptor of arylpalladium intermediates in the formation of a congested benzylic quaternary carbon center through an intramoleculer Mizoroki-Heck reaction. The cis B/C ring system was stereoselectively converted to the trans-fused framework through a SmI2-promoted deoxygenation of the alpha-hydroxy ketone.