The Stannides YNi x Sn2 ( x = 0, 0.14, 0.21, 1) – Syntheses, Structure, and 119Sn M?ssbauer Spectroscopy

Summary. The stannides YNi _x Sn₂ (x = 0, 0.14, 0.21, 1) were prepared by arc-melting of the pure elements. They were characterized through X-ray powder and single crystal data: ZrSi₂ type, space group Cmcm, a = 438.09(6), b = 1629.6(4), c = 430.34(7) pm, wR2 = 0.0607, 386 F ² values, 14 variables for YSn₂, CeNiSi₂ type, Cmcm, a = 440.6(1), b = 1640.3(1), c = 433.0(1) pm, wR2 = 0.0632, 416 F ² values, 19 variables for YNi_0.142(7)Sn₂, a = 441.0(1), b = 1646.3(1), c = 434.6(1) pm, wR2 = 0.0491, 287 F ² values, 19 variables for YNi_0.207(7)Sn₂, and LuNiSn₂ type, space group Pnma, a = 1599.3(3), b = 440.89(5), c = 1456.9(2) pm, wR2 = 0.0375, 1538 F ² values, 74 variables for YNiSn₂. The YSn₂ structure contains Sn1–Sn1 zig-zag chains (297 pm) and planar Sn2 networks (307 pm). The stannides YNi_0.142(7)Sn₂ and YNi_0.207(7)Sn₂ are nickel filled versions of YSn₂. The nickel atoms have a distorted pyramidal tin coordination with Ni–Sn distances ranging from 220 to 239 pm. New stannide YNiSn₂ adopts the LuNiSn₂ type. The nickel and tin atoms build up a complex three-dimensional [NiSn₂] network in which the yttrium atoms fill distorted pentagonal and hexagonal channels. Within the network all nickel atoms have a distorted square pyramidal tin coordination with Ni–Sn distances ranging from 247 to 276 pm. Except the Sn4 atoms which are located in a tricapped trigonal Y₆ prism, all tin atoms have between 4 and 5 tin neighbors between 297 and 350 pm. ¹¹⁹Sn M?ssbauer spectroscopic data of YNi _x Sn₂ show a decreasing isomer shift (from 2.26 to 2.11 mm/s) from YSn₂ to YNiSn₂, indicating decrease of the s electron density at the tin nuclei.     

Si-Containing Amides of Phosphoric Acid

Summary. The first representative of the N-silylmethylamides of phosphoric acid O=P[NMe(CH₂SiMe _n (OEt)_3-n ]₃ have been synthesized by interaction of MeNHCH₂SiMe _n (OEt)_3-n (n = 2, 3) with POCl₃. The interaction of the N,N′,N″-trimethyl-N,N′,N″-tris[(ethoxydimethyl- silyl)methyl]triamide phosphoric acid with BF₃·Et₂O or BCl₃ results in the formation of the N,N′,N″-trimethyl-N,N′,N″-tris[(fluorodimethyl-silyl)methyl]triamide phosphoric acid or N,N′,N″-trimethyl-N,N′,N″-tris[(chlorodimethylsilyl)methyl]triamide phosphoric acid. NMR data show on the tetracoordinate state of silicon in these products. Professor Vadim Aleksandrovich Pestunovich, our chief, teacher and friend died on July 4^th, 2004     

Conformational Analysis,Infrared, and Fluorescence Spectra of 1-Phenyl-1,2-propandione 1-oxime and Related Tautomers: Experimental and Theoretical Study

Summary. Conformational analysis and frequency calculation were achieved for 1-phenyl-1,2-propandione 1-oxime and its four tautomers: 1-nitroso-1-phenyl-1-propen-2-ol, 1-nitroso-1-phenyl-2-propanone, 2-hydroxy-1-phenyl-propenone oxime, and 3-nitroso-3-phenyl-propen-2-ol. Calculations were carried out at the Hartree–Fock (HF), Density Functional Theory (B3LYP), and the second-order M?ller–Plesset perturbation (MP2) levels of theory using 6-31G^* and 6-311G^** basis sets. Five conformers with no imaginary vibrational frequency were obtained by free rotations around three single bonds of 1-phenyl-1,2-propandione-1-oxime: Ph–C(NOH)C(O)CH₃, PhC(NOH)–C(O)CH₃, and PhC(N–OH)C(O)CH₃. Similarly, eight structures with no imaginary vibrational frequency were encountered upon rotations around three single bonds of 1-nitroso-1-phenyl-1-propen-2-ol: Ph–C(NO)C(OH)CH₃, PhC(N–O)C(OH)CH₃, and PhC(NO)C(–OH)CH₃. In the same manner, six minima were found through rotations around three single bonds of 1-nitroso-1-phenyl-2-propanone: Ph–CH(NO)C(O)CH₃, PhCH(–NO)C(O)CH₃, and PhCH(NO)–C(O)CH₃. Also, two minima were found through rotations around four single bonds of 2-hydroxy-1-phenyl-propenone oxime: Ph–C(NOH)C(OH)CH₂, PhC(N–OH)C(OH)CH₂, PhC(NOH)–C(OH)CH₂, and Ph-C(NOH)C(–OH)CH₂. Finally, two minima were found through rotations around four single bonds of 3-nitroso-3-phenyl-propen-2-ol: Ph–CH(NO)C(OH)CH₂, PhCH(–NO)C(OH)CH₂, PhCH(NO)–C(OH)CH₂, and PhCH(NO)C(–OH)CH₂. Interconversions within the above sets of conformers were probed through scanning (one and/or two dimensional), and/or QST3 techniques. The order of the stability of global minima encountered was: 1,2-propandione-1-oxime > 1-nitroso-1-phenyl-2-propanone > 1-nitroso-1-phenyl-1-propen-2-ol > 2-hydroxy-1-phenyl-propenone oxime > 3-nitroso-3-phenyl-propen-2-ol. Hydrogen bonding appears significant in tautomers of 1-nitroso-1-phenyl-1-propen-2-ol and 2-hydroxy-1-phenyl-propenone oxime. The CIS simulated λ_max for the first excited singlet state (S₁) of 1-phenyl-1,2-propandione 1-oxime is 300.4 nm, which was comparable to its experimental λ_max of 312.0 nm. The calculated IR spectra of 1-phenyl-1,2-propandione 1-oxime and its tautomers were compared to the experimental spectra.     

Polyhalite and its analogous triple salts

Polyhalite (K₂SO₄ · MgSO₄ · 2CaSO₄ · 2H₂O) and analogue triple salts, where Mg²⁺ is substituted by Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺, have been synthesized. The salts were characterized by thermal analysis, Raman spectroscopy and X-ray powder diffraction. Diffraction patterns and Raman spectra resemble those of natural polyhalite, except K₂SO₄ · CuSO₄ · 2CaSO₄ · 2H₂O. The latter corresponds to the mineral leightonite, which is structurally different. For polyhalite analogues the cell parameters of the triclinic unit cell have been determined from the powder diffraction patterns. The length of the unit cell vectors varies regularly with the ionic radius of the substituted ion M ²⁺ and is explained by changes in the extension of the coordination octahedron of M ²⁺. Thereby increasing distances of the coordinated water molecules at M ²⁺ parallel with decreasing dehydration temperatures of the corresponding polyhalite. Correspondence: Daniela Freyer, Institut für Anorganische Chemie, TU Bergakademie Freiberg, 09599 Freiberg, Germany.     

Detours for Reaching at New Germylenes,Silylenes, Carbenes,and Carbenogermylenes through Substituted Cyclopropenylidenes at <Emphasis Type="Italic">Ab initio</Emphasis> and DFT Levels

Summary. Heavier atom containing X ₂SiC₂, and X ₂GeC₂ cyclopropenylidenes transform into new silylenes, germylenes, and carbenogermylenes at DFT and ab initio levels (X = H, CN, NH₂, and OMe). The number of transformations or rearrangements appear roughly proportional to the covalent radii of the group 14 elements (Ge > Si > C).     

Amino Acid Derivatives,V [1]: Synthesis and Antiviral Evaluation of α-Amino Acid Esters Bearing an α-<Emphasis Type="SmallCaps">d</Emphasis>-Mannofuranoside Side Chain

Summary. d-Mannose was treated with dry acetone in the presence of conc. H₂SO₄ to afford 2,3:5,6-di-O-isopropylidene-α-d-mannofuranoside. Treating the latter with ethyl chloroacetate gave carboethoxymethyl 2,3:5,6-di-O-isopropylidene-α-d-mannofuranoside, which was hydrolyzed with N₂H₄ · H₂O to afford the acid hydrazide derivative. Treating of the acid hydrazide with acylated amino acides, via the azide-coupling method afforded the corresponding O-glycopeptides. Reaction of the glycopeptide methyl esters with N₂H₄ · H₂O afforded the corresponding hydrazides, which were coupled with the amino acid methyl esters to afford the dipeptides. Deprotection was carried out by using 70% AcOH. The prepared O-glycopeptides were tested for antiviral activity against hepatitis B virus and showed moderate activities.     

Deprotonated and non-deprotonated cobalt(II) complexes of the bis-amide tetradentate ligand N,N′-(dipicolyl)-1,8-naphthylene diamine. Three different modes of coordination by the ligand

The preparation and some properties of the cobalt(II) complexes Co(LH₂)Cl₂·2H₂O, Co(LH₂(NCS)₂ and CoL·H₂O (whereLH₂=N,N-(dipicolyl)-1,8-naphthylenediamine) are reported. On the basis of magnetic moments, visible reflectance and IR data, the structure is proposed to be pseudo-octahedral for Co(LH₂)Cl₂·2 H₂O, pseudo-tetrahedral for Co(LH₂)(NCS)₂ and square planar for CoL·H₂O.

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Deprotonierte und Nicht-deprotonierte Co(II)-Komplexe des vierzähnigen Bisamid-Liganden N,N-(Dipicolyl)-1,8-naphthyldiamin. Drei verschiedene Koordinationstypen

Zusammenfassung Es werden die Darstellung und einige Eigenschaften der Kobalt(II)-Komplexe Co(LH₂)Cl₂·2 H₂O, Co(LH₂)(NCS)₂ und CoL·H₂O [LH₂=N,N-(dipicolyl)-1,8-naphthylendiamin] diskutiert. Auf der Grundlage von magnetischen Momenten, von Daten der sichtbaren Reflektions-und IR-Spektren wird eine pseudooctaedrische Struktur für Co(LH₂)Cl₂·2H₂O, eine pseudotetraedrische für Co(LH₂)(NCS)₂ und eine planar-quadratische für CoL·H₂O vorgeschlagen.

     

X-Ray and TEM Studies of CdTeMoO6 and CoTeMoO6: A New Superstructure of Fluorite Type with Cation and Anion Deficiencies (▪CoTeMo)(□2O6)

The crystal structures of two telluromolybdates CdTeMoO₆ and CoTeMoO₆ have been solved ab initio. CdTeMoO₆ crystallizes in a tetragonal cell (space group No. 113, P 2₁m, Z=2) with a=5.2840(1) Å, c=9.0595(2) Å whereas CoTeMoO₆ crystallizes in orthorhombic space group P2₁2₁2 (No. 18) with two formula units in the unit cell of dimensions a=5.2545(1) Å, b=5.0653(1) Å, and c=8.8589(2) Å. The X-ray powder diffraction pattern data were refined by the Rietveld profile technique and led respectively to R_Bragg=0.07 for CdTeMoO₆ and R_Bragg=0.07 for CoTeMoO₆. The crystal structure of CdTeMoO₆ is built up from corner-sharing distorted CdO₄ tetrahedra which build a layer in the a,b plane, while in CoTeMoO₆ cobalt atoms exhibited an octahedral distorted surrounding. Both compounds are simultaneously cation- and anion-deficient 1.1.2 superstructures of fluorite in which the electron lone pairs of tellurium are stereo-chemically active. High-resolution electron microscopy images of CdTeMoO₆ showed well-ordered crystals fragments, but in some crystals defects have also been detected.     

Preparation and Characterization of a Stable Semiquinone-Iron Complex

Summary. Dopamine oxidation by iron oxide (Fe₂O₃) was studied in the presence and absence of sodium thiosulfate in aqueous medium around pH 7 by UV-Vis spectroscopy. The pH changes from 6 to 8 indicate that the dopamine oxidation process has occurred producing an anionic semiquinone radical which appears after ca. 100 hours presenting bands at 309 and 337nm. It forms a stable compound with Fe(III) released by the iron oxide. The complex [CTA][Fe(SQ)₂(CAT)], where SQ=semiquinone, CAT=catecholate, and CTA=cetyltrimethylammonium cation, was isolated by precipitation with cetyltrimethylammonium bromide and was characterized through EPR, Raman and IR spectroscopies. The EPR spectrum presented two intense bands, one with g=2.003 assigned to o-semiquinone and the other with g=4.274 characteristic for high spin Fe(III) approaching an octahedral symmetry. The most intense Raman resonance band occurs at 1360cm^–1 assigned to (C₁–C₂) and at 1575cm^–1 to (C–C)ring of the o-semiquinone. The O₂ dissolved in solution is mainly responsible for the dopamine oxidation when sodium thiosulfate is present. A thermal decomposition mechanism based on the thermogravimetric curves (TG) was proposed. These results suggest that iron can participate in the degenerative process of the dopaminergic nigral neurons. Its role seems to be its coordination with the dopamine oxidation products as o-semiquinone and catecholate which could damage neurons giving rise to parkinsonism.     

金属离子化合物抗菌活性的微量热法

用微量热法测定了大肠杆菌在四种金属离子化合物作用下的生长代谢热谱。计算了大肠杆菌在指数生长期的生长速率常数k、传代时间G、生长抑制率I和发热量Q等参数；建立了热谱信息参量之间的关系，定量地讨论了金属离子化合物对大肠杆菌生长代谢的抑制，并发现可用P_max和t_r表征大肠杆菌和生长代谢的化合物的抗菌活性。     

Crystal Structure and Spectral Characterization of a Rare Example of a Salen-Type Zinc Complex with Neutral Monodentate Oxygen Donor Ligands Coordination

Summary. The new zinc complex of the N,N′-bis(salicylidene)-4-methyl-1,3-phenylenediamine ligand as a product of the [2 + 1] Schiff base condensation process was synthesized in the one-step metal-promoted reaction between salicylaldehyde and 4-methyl-1,3-phenylenediamine in ethanol in the presence of zinc chloride. The two potentially tetradentate N₂O₂ Schiff bases function as neutral monodentate ligands involving only one oxygen atom in coordination. This rare coordination pattern of a mononuclear salen-type zinc complex was revealed by X-ray crystallography and correlated with spectroscopic characterization.     

Schiff base complexes of dioxouranium(VI). VII. Dioxouranium(VI) acetate complexes with monobasic bidentate and bibasic tridentateSchiff bases

11 and 12 molar reactions of dioxouranium(VI) acetate dihydrate with the monobasic bidentateSchiff bases,o-HOC₆H₄CH=NR oro-HOC₁₀H₆CH=NR (R=C₂H₅,n-C₃H₇,n-C₄H₉ or C₆H₅) and bibasic tridentateSchiff bases,o-HOC₆H₄CH=NR(OH) oro-HOC₁₀H₆CH=NR(OH) (R=–CH₂CH(CH₃)- or —CH₂CH₂CH₂–) have been studied and derivates of the type UO₂(OAc)₂(SBH), UO₂(OAc)₂(SBH)₂, UO₂(OAc)₂(SBH ₂) and UO₂(OAc)₂(SBH ₂)₂ (whereSBH andSBH ₂ represent monobasic bidentate and bibasic tridentateSchiff base molecules respectively) have been isolated. These have been characterized by elemental analysis, conductance measurements and IR spectral studies.

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UO₂ ²⁺-Komplexe von Schiff-Basen. VII. Uranylacetat-Komplexe mit monobasischen zweizähnigen und bibasischen dreizähnigen Schiff-Basen

Zusammenfassung Es wurden in 1:1- und 1:2-molaren Reaktionen von UO₂(OAc)₂·2H₂O mitSchiff-Basen (L) Komplexe des Typs UO₂(OAc)₂ L bzw. UO₂(OAc)₂ L ₂ isoliert. Die Komplexe wurden mittels Elementaranalyse, Leitfähigkeitsmessungen und IR-Spektren untersucht.

     

Green protocol for conjugate addition of amines to p-quinones accelerated by water

Amines undergo smooth conjugate addition to p-quinones in H₂O at ambient temperature in the absence of a catalyst to produce 2-aminoquinones in excellent yields. Significant rate acceleration of this reaction is observed in H₂O compared to organic solvents. H₂O played a dual role in simultaneously activating the p-quinone and amine. This new methodology constitutes an easy, highly efficient, and green synthesis of substituted p-quinones. Correspondence: J. S. Yadav, Division of Organic Chemistry, Indian Institute of Chemical Technology, Hyderabad 500007, India.     

Mild and Efficient Synthesis of Benzoxazoles, Benzothiazoles, Benzimidazoles, and Oxazolo[4,5-b]pyridines Catalyzed by Bi(III) Salts Under Solvent-Free Conditions

Summary. A series of benzoxazoles, benzothiazoles, benzimidazoles, and oxazolo[4,5-b]pyridines was efficiently synthesized from the reactions of o-aminophenols, o-aminothiophenol, o-phenylenediamines, and 2-amino-3-hydroxypyridine with orthoesters in the presence of catalytic amounts of Bi(III) salts, such as Bi(TFA)₃, Bi(OTf)₃, and BiOClO₄ · xH₂O under solvent-free conditions. The remarkable features of this new protocol are high conversion, very short reaction times, cleaner reaction profiles under solvent-free conditions, straightforward procedure, and use of relatively non-toxic catalysts.     

Asymmetrische Hg(II)-Komplexe mit Organothiolato- bzw. Organoselenolato-und Triazenato-Liganden

The mixed mercury complexes (2XC₆H₄)₂N₃HgY (X=CH₃, F, Cl, Br, I;Y=SC₂H₅, SC₆H₅, SeC₆H₅) have been prepared. Both the Hg–S and Hg–Se bonds and, in contrast to other mixed triazenato-mercury compounds, the triazenato-mercury bonds have been shown to be kinetically labile on the NMR time scale by means of⁷⁷Se and¹⁹⁹Hg NMR spectroscopy. Evidence has been obtained for the presence of (2XC₆H₄)₂N₃HgY together with HgY ₂ and [(2XC₆H₄)₂N₃]₂Hg in solution.

     

Transition metal chemistry of oxime-containing ligands,IX

The vibrational (conventional and far-infrared) and diffuse-reflectance spectra in conjunction with magnetic susceptibility measurements over a temperature range down to liquid nitrogen temperature are reported and discussed for the complexes; [Mn(HPOX)₂ X ₂]; [Mn(HMPX)₂ X ₂]; [Fe(HPOX)(POX) X ₂] and [Fe(HMPX)(MPX) X ₂](whereHPOX=pyridine-2-aldoxime (C₆H₆N₂O);POX=C₆H₅N₂O;HMPX=6-Methylpyridine-2-aldoxime (C₇H₈N₂O);MPX=C₇H₇N₂O;X=Cl, Br, I, NO₃, NCS, or OA c andX ₂=SO₄). On the basis of these physical studies a six-coordinated structure is suggested for the manganese(II) and iron(III) complexes.Mössbauer spectra, measured at room-temperature and liquid nitrogen temperature also indicated a six-coordinate geometry for iron(III) complexes.

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Übergangsmetallkomplexe mit Oxim-enthaltenden Liganden, IX. Spektroskopische und magnetische Untersuchungen von Mn(II)- und Fe(II)-Komplexen mit Pyridin-2-aldoxim und 6-Methylpyridin-2-aldoxim

Zusammenfassung Es wurden Komplexe von Pyridin-2-aldoxim (HPOX) und 6-Methylpyridin-2-aldoxim (HMPX) vom Typ [Mn(HPOX)₂ X ₂], [Mn(HMPX)₂ X ₂], [Fe(HPOX)(POX)X ₂] und [Fe(HMPX)(MPX)X ₂] (X=Cl, Br, I, NO₃, NCS, OA c;X ₂=SO₄) dargestellt. Die Diskussion erfolgt basierend auf Infrarot-spektroskopie (inklusive fernes IR), Messungen der magnetischen Suszeptibilität (Temp. bis zu fl. N₂) undMössbauer-Spektroskopie.

     

Stereodivergent <Emphasis Type="Italic">Baylis-Hillman</Emphasis> Reaction of a Chiral Acryloyl Imide Exploiting Ion-Chelation Effect: Mechanistic Insight on the Rearrangement of Trichloroacetimidates of the <Emphasis Type="Italic">Baylis-Hillman</Emphasis> Adducts to Trichloroacetamides

Summary. In the presence of DABCO, ethyl glyoxalate and (4S,5R)-1,5-dimethyl-3-acryloyl-4-phenylimidazolidin-2-one gave mixtures of the corresponding Baylis-Hillman adducts enriched in either isomer, depending on the absence or the presence of LiClO₄ in the reaction mixture. A diastereomeric mixture in 10:90 dr allowed to definitively establish the mechanism of the reaction leading to trichloroacetamides starting from trichloroacetimidates of the Baylis-Hillman adducts.     

Kolbe-Schmitt reaction of sodium 2-naphthoxide

The mechanism of the Kolbe-Schmitt reaction of sodium 2-naphthoxide is examined by means of the B3LYP/LANL2DZ method. After the initial formation of sodium 2-naphthoxide-CO₂ complex, the carbon of the CO₂ moiety performs an electrophilic attack on the naphthalene ring. Further transformations lead to the formation of sodium 2-hydroxy-1-naphthoate. Sodium 3-hydroxy-2-naphthoate is formed by a 1,3-rearrangement of the CO₂Na group. Our findings are in good agreement with the experimental results on the carboxylation reaction of sodium 2-naphthoxide. Correspondence: Svetlana Marković, Faculty of Science, University of Kragujevac, 34000 Kragujevac, Serbia     

Alum (KAl(SO<Subscript>4</Subscript>)<Subscript>2</Subscript> · 12H<Subscript>2</Subscript>O) Catalyzed One-Pot Synthesis of Coumarins under Solvent-Free Conditions

Summary. Alum (KAl(SO₄)₂ · 12H₂O) is used as an efficient catalyst in the Pechmann condensation of phenol derivatives with β-keto esters leading to the formation of coumarins in excellent yields under solvent-free conditions. This methodology offers significant improvements for the synthesis of coumarins with regard to the yield of products, simplicity in operation, and green aspects by avoiding toxic catalysts and solvents.     

The vibrational spectra of linear and branched perchlorosilanes Si n Cl2n+2 and their simulation using a local symmetry force field

Infrared andRaman vibrational spectra ofn-Si₄Cl₁₀,n-Si₅Cl₁₂,neo-Si₅Cl₁₂ and [(SiCl₃)₃Si]₂ have been measured and assigned. A local symmetry force field has been developed to simulate vibrational spectra of all (noncyclic) perchlorosilanes Si _n Cl_2n+2 known today (n=2, 3, 4, 5, 8). The observed spectra are reproduced satisfactorily

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Die Vibrationsspektren linearer und verzweigter PerchlorsilaneSi _n Cl _2n+2 und deren Simulierung mittels eines lokalen Symmetrie-Kraftfeldes

Zusammenfassung Infrarot- undRaman-Spektren vonn-Si₄Cl₁₀,n-Si₅Cl₁₂,neo-Si₅Cl₁₂ und [(SiCl₃)₃Si]₂ wurden aufgenommen und zugeordnet. Ein lokales Symmetrie-Kraftfeld zur Simulation der Spektren aller bisher bekannten (nicht cyclischen) Perchlorsilane Si _n Cl_2n+2 (n=2, 3, 4, 5, 8) wird angegeben. Die beobachteten Spektren werden zufriedenstellend reproduziert