- Autocatalysis and surface catalysis in the reduction of imines by SmI 2
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The reduction of the three imines, N-benzylidene aniline (BAI), N-benzylidenemethylamine (BMI), and benzophenone imine (BPI), with SmI 2 gives the reduced as well as coupled products. The reactions were found to be autocatalytic due to the formation of the trivalent samarium in the course of the reaction. When preprepared SmI3 was added to the reaction mixture, the reaction rate increased significantly. However, the kinetics were found to be of zero order in SmI2. This type of behavior is typical of surface catalysis with saturation of the catalytic sites. Although no solids are visible to the naked eye, the existence of microcrystals was proven by light microscopy as well as by dynamic light scattering analysis. Although HRTEM shows the existence of quantum dots in the solid, we were unable to make a direct connection between the existence of the quantum dots and the catalytic phenomenon. In the uncatalyzed reaction, the order of reactivity is BPI > BMI > BAI. This order does not conform to the electron affinity order of the substrates but rather to the nitrogen lone pair accessibility for complexation. This conclusion was further supported by using HMPA as a diagnostic probe for the existence of an inner sphere electron transfer reaction.
- Rao, Chintada Nageswara,Hoz, Shmaryahu
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- Studies on organolanthanoid complexes LI. Syntheses of bis- and tris(2-methoxyethylcyclopentadienyl) lanthanoid complexes and crystal structures of bis(2-methoxyethylcyclopentadienyl)ytterbium iodide and tris(2-methoxyethylcyclopentadienyl)samarium
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Reactions of lanthanoid triiodides (Ln = Sm, Yb) with two or three equivalents of 2-methoxyethylcyclopentadienyl potassium salt in tetrahydrofuran afford bis(2-methoxyethylcyclopentadienyl) lanthanoid iodide complex Cp'2YbI (I) (Cp' = MeOCH2CH2C5H4), tris(2-methoxyethylcyclopentadienyl) lanthanoid complexes Cp'3Sm (II) and Cp'3Yb (III), respectively.The compound Cp'2YbI (I) crystallizes from THF/hexane in orthorhombic space group P212121 with cell dimensions a = 10.892(2), b = 12.278(3), c = 12.805(5) Angstroem, V = 1712.4 Angstroem3, Dcalcd = 2.118 g cm-3for Z = 4.The central metal Yb is coordinated by two Cp' ring centroids, one iodine atom and two oxygen atoms of Cp' forming a distorted trigonal bipyramid.The crystal of Cp'3Sm (II) belongs to the monoclinic crystal system, space group P21/n with a = 8.415(7), b = 20.439(3), c = 12.926(2) Angstroem, β = 90.34(3) deg, V = 2223.2 Angstroem3, Dcalcd = 1.562 g cm-3 and Z = 4.The three Cp' ring centroids and two oxygen atoms of Cp' describe a trigonal bipyramid around the central ion of samarium.Complexes I, II and III are all unsolvated monomeric molecules with higher coordination number.
- Deng, Daoli,Qian, Changtao,Song, Fuquan,Wang, Zhaoyu,Wu, Guang,et al.
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- Reinvestigation of the Reaction of Samarium Metal with Mercury(II) Iodide
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Samarium(II) iodide is obtained from reaction of mercury(II) iodide with an excess of samarium metal in boiling tetrahydrofuran.The preparation involves formation and reduction of samarium(III) iodide and is affected by the quality of the samarium metal.
- Deacon, Glen B.,Forsyth, Craig M.
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- Structural characterization of methanol substituted lanthanum halides
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The first study into the alcohol solvation of lanthanum halide [LaX3] derivatives as a means to lower the processing temperature for the production of the LaBr3 scintillators was undertaken using methanol (MeOH). Initially the de-hydration of {[La(μ-Br)(H2O)7](Br)2}2 (1) was investigated through the simple room temperature dissolution of 1 in MeOH. The mixed solvate monomeric [La(H2O)7(MeOH)2](Br)3 (2) compound was isolated where the La metal center retains its original 9-coordination through the binding of two additional MeOH solvents but necessitates the transfer of the innersphere Br to the outersphere. In an attempt to in situ dry the reaction mixture of 1 in MeOH over CaH2, crystals of [Ca(MeOH)6](Br)2 (3) were isolated. Compound 1 dissolved in MeOH at reflux temperatures led to the isolation of an unusual arrangement identified as the salt derivative {[LaBr2.75·5.25(MeOH)]+0.25 [LaBr3.25·4.75(MeOH)]-0.25} (4). The fully substituted species was ultimately isolated through the dissolution of dried LaBr3 in MeOH forming the 8-coordinated [LaBr3(MeOH)5] (5) complex. It was determined that the concentration of the crystallization solution directed the structure isolated (4 concentrated; 5 dilute) The other LaX3 derivatives were isolated as [(MeOH)4(Cl)2La(μ-Cl)]2 (6) and [La(MeOH)9](I)3·MeOH (7). Beryllium Dome XRD analysis indicated that the bulk material for 5 appear to have multiple solvated species, 6 is consistent with the single crystal, and 7 was too broad to elucidate structural aspects. Multinuclear NMR (139La) indicated that these compounds do not retain their structure in MeOD. TGA/DTA data revealed that the de-solvation temperatures of the MeOH derivatives 4-6 were slightly higher in comparison to their hydrated counterparts.
- Boyle, Timothy J.,Ottley, Leigh Anna M.,Alam, Todd M.,Rodriguez, Mark A.,Yang, Pin,Mcintyre, Sarah K.
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p. 1784 - 1795
(2010/07/03)
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- Thermal constants of melting of samarium(III) iodide
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SmI3 samples were prepared by iodination of metal samarium with iodine vapor and identified by chemical analyses and X-ray powder diffraction. The melting point (Tm(SmI3) = 1145 ± 9 K) and the enthalpy of melting (ΔmH°(SmI3) = 25.9 ± 2.5 kJ/mol) were determined. The entropy of melting ΔmS° (SmI3) was calculated to be 22.6 ± 3 J/(mol K).
- Poshevneva,Goryushkina,Vinokurova,Goryushkin
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p. 181 - 182
(2008/10/08)
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- X-ray powder diffraction study of samarium iodide
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From X-ray powder diffraction patterns of SmI3 prepared by the iodination of the metal by iodine vapor, diffraction characteristics and crystallographic values were determined for the third polymorph of samarium iodide (undescribed previously), which has a tetragonal structure: a = 1.964(8) ?, c = 14.223(10) ?, ρX-ray = 5.087 g/cm3, Z = 16.
- Astakhova,Goryushkin
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p. 1551 - 1553
(2008/10/08)
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- Rare earth iodide complexes of 4-formyl-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one
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Rare earth complexes of 4-formyl-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one (FDPP) having the general formula [Ln(FDPP)4I2]I, where Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Dy, Ho and Er, have been synthesised and characterised by elemental analyses, molar conductance in non-aqueous solvents, electronic, infrared and proton NMR spectra as well as thermogravimetric analyses. FDPP acts as a neutral monodentate ligand coordinating through the ring carbonyl oxygen. Two of the iodide ions are coordinated. A coordination number of six may be assigned to the metal ion in these complexes. The covalency parameters evaluated from the solid state electronic spectra suggest weak covalent character of the metal-ligand bond. The TG data of the lanthanum complex indicate that the complex is stable up to about 140° C and undergoes decomposition in three stages forming lanthanum oxide as the final product.
- Joseph, Siby,Radhakrishnan
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p. 1219 - 1229
(2008/10/09)
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- A new convenient preparation of monocyclooctatetraenyl-lanthanide complexes from metallic lanthanides and oxidants
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Treatment of lanthanide metals with cyclooctatetraene in the presence of an equimolar amount of iodine afforded cyclooctatetraenyl-iodolanthanide(III) complexes, LnI(η8-cot)(thf)n (cot = cyclooctatetraenyl; 1a: Ln = La, n = 3; 1b: Ln = Ce, n = 3; 1c: Ln = Pr, n = 3; 1d: Ln = Nd; n = 2; 1e: Ln = Sm, n = 1), in modest yields.Bromo and chloro-bridged dinuclear complexes of samarium, 2 (2: X = Br; 3: X = Cl), are also prepared by the reaction of samarium metal with cyclooctatetraene in the presence of 1,2-dibromoethane or Ph3PCl2, respectively.The reaction of metallic samarium with cyclooctatetraene and diaryl disulfide or diphenyl diselenide in THF afforded cyclooctatetraenyl-thiolate or - selenolate complexes of samarium(III), 8-cot)(thf)n>2 (4a: EAr = SPh, n = 2; 4b: SC6H2Me3-2,4,6, n = 2; 4c: SC6H2iPr3-2,4,6, n = 1; 5: SePh, n = 2).The dimeric structure of 5 was revealed by X-ray crystallography 1/n with a = 8.500(5), b = 21.805(6), c = 12.042(5) Angstroem, β = 105.98(4) deg, V = 2145(1) Angstroem3, Z = 2, R = 0.055 for 2061 reflections with I > 3?(I) and 235 parameters>.A samarium(II) complex, 8-cot)(thf)>n (6), was also obtained by the direct reaction of samarium metal with cyclooctatetraene in THF with a catalytic amount of iodine.Reaction of 6 with iodine and diphenyl disulfide afforded 1e and 4a, respectively. Key words: Lanthanide; Cyclooctatetraenyl; Thiolate; Selenolate; Samarium
- Mashima, Kazushi,Nakayama, Yuushou,Nakamura, Akira,Kanehisa, Nobuko,Kai, Yasushi,Takaya, Hidemasa
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- Selective catalyzed-rearrangement of terminal epoxides to methyl ketones
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Terminal epoxides of the type {A figure is presented} have been selectively converted into methyl ketones by various catalysts. Some lanthanide derivatives, MnI2, and Co2(CO)8 gave the best results. The rearrangement of internal epoxides into ketones is much slower, allowing specific transformation of terminal epoxides. The scope of the reaction and tentative mechanisms are discussed.
- Prandi,Namy,Menoret,Kagan
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p. 449 - 460
(2007/10/02)
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