Die Kristallstruktur von Gd6Cu8Ge8 und isotypen Phasen

Zusammenfassung Die Verbindungen Gd(Dy, Er, Lu)₆Cu₈Ge₈ wurden hergestellt und ihre Struktur bestimmt. Gd₆Cu₈Ge₈ kristallisiert orthorhombisch in einem neuen Strukturtyp mita=14,000±0,008 Å,b=6,655±0,003 Å,c=4,223±0,004 Å, Raumgruppe D _2h ²⁵ -I mmm mit 2 Gd in 2 (d), 4 Gd in 4 (e), 8 Cu in 8 (n), 4 Ge in 4 (f) und 4 Ge in 4 (h), N=1. Die Struktur ist durch Verwandtschaft zum AlB₂- und CaZn₅-Typ gekennzeichnet. Die anderen genannten Phasen sind dem Gd₆Cu₈Ge₈ isotyp.

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Crystal structure of Gd₆Cu₈Ge₈, and of isotypic phases

The compounds Gd(Dy, Er, Lu)₆Cu₈Ge₈ have been prepared and their structure has been determined. Gd₆Cu₈Ge₈ crystallizes in a new structure type witha=14.000±0.008 Å,b=6.655±0.003 Å,c=4.223±0.004 Å, space group D _2h ²⁵ -I mmm with 2 Gd in 2 (d), 4 Gd in 4 (e), 8 Cu in 8 (n), 4 Ge in 4 (f) and 4 Ge in 4 (h), N=1. The structure is characterized by close relationship to the AlB₂ and CaZn₅ structure types. The other phases mentioned above are isotypic to Gd₆Cu₈Ge₈.

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Mit 4 Abbildungen     

Synthesis,Base Pairing,and Structural Transitions of Oligodeoxyribonucleotides Containing 8-Aza-2′-deoxyguanosine

The synthesis of oligonucleotides containing 8-aza-2′-deoxyguanosine (z⁸G_d; 1 ) or its N⁸-regioisomer z⁸G_d^* ( 2 ) instead of 2′-deoxyguanosine (G_d) is described. For this purpose, the NH₂ group of 1 and 2 was protected with a (dimethylamino)methylidene residue (→ 5, 6 ), a 4,4′-dimethoxytrityl group was introduced at 5′-OH (→ 7, 8 ), and the phosphonates 3a and 4 as well as the phosphoramidite 3b were prepared. These building blocks were used in solid-phase oligonucleotide synthesis. The oligonucleotides were characterized by enzymatic hydrolysis and melting curves (T_m values). The thermodynamic data of the oligomers 12–15 indicate that duplexes were stabilized when 1 was replacing G_d. The aggregation of d(T-G-G-G-G-T) ( 18 ) was studied by RP 18 HPLC, gel electrophoresis and CD spectroscopy and compared with that of oligonucleotides containing an increasing number of z⁸G_d residues instead of G_d. Similarly to [d(C-G)]₃ ( 12a ), the hexamer d(C-z⁸G-C-z⁸G-C-G) ( 14 ) underwent salt-dependent B-Z transition.     

Crown‐Ether‐Like Structures Derived from a Ti8O8(Carboxylate)16 Metallacycle

Mixed‐metal clusters have been obtained from the reaction of titanium alkoxides with either strontium or lead acetate and methacrylic acid. The structures of the clusters are derived from the metallacycle Ti₈O₈(methacrylate)₁₆. The Sr and Pb atoms in Sr₂Ti₈O₈X₂(OOCMe)₂(methacrylate)₁₆ (X: acetate or OiPr) and Pb₂Ti₈O₈(OBu)₂X₂(methacrylate)₁₆(BuOH)₂ (X: acetate or methacrylate) occupy the central cavity of the Ti₈O₈ ring. In addition to the crown‐ether‐like coordination of the ring oxygen atoms to the Sr or Pb atoms, bridging carboxylate ligands support the coordination of the latter atoms. In the compound Pb₂Ti₆O₅(OiPr)₃X(methacrylate)₁₄ (X: OiPr or methacrylate), the lead atoms are coordinated by a fragment of the Ti₈O₈(methacrylate)₁₆ metallacycle.     

Synthesis and Characterization of the New Copper Indium Phosphate Cu8In8P4O30

The system CuO/In₂O₃/P₂O₅ has been investigated using solid state reaction between CuO, In₂O₃ and (NH₄)₂HPO₄ in silica glass crucibles at 900 °C. The powder samples were characterized by X‐ray diffraction, thermal analysis and FT‐IR spectroscopy. Orange single crystals of the new quaternary phase were achieved by the process of crystallization with mineralizers in sealed silica glass ampoules. They were then analyzed with EDX and single‐crystal X‐ray analysis in which the composition Cu₈In₈P₄O₃₀ with the triclinic space group P$\bar{1}$ (No 2) with a = 7,2429(14) Å, b = 8,8002(18) Å, c = 10,069(2) Å, α = 103,62(3)°, β = 106,31(3)°, γ = 101,55(3)° and Z = 1 was found. The three‐dimensional framework consists of [InO₆] octahedra and distorted [CuO₆] octahedra, overcaped [InO₇] prisms and [PO₄] tetrahedra, also trigonal [(CuIn)O₅] bipyramids and distorted [(CuIn)O₆] octahedra, where copper and indium are partly exchanged against each other. Cu₈In₈P₄O₃₀ exhibits an incongruent melting point at 1023 °C.     

A S8‐like [Sb8]8− Zintl Anion in the Ammoniate [K17(Sb8)2(NH2)] · 17.5NH3

The ammoniate [K₁₇(Sb₈)₂(NH₂)] · 17.5NH₃ was synthesized by reduction of antimony with potassium in liquid ammonia. Single crystals were isolated and characterized by low temperature X‐ray structure analysis. [K₁₇(Sb₈)₂(NH₂)] · 17.5NH₃ crystallizes in the space group P2₁/c (No. 14) with a = 12.976(1) Å, b = 24.536(1) Å, c = 22.858(1) Å and β = 99.17(1)°. The ammoniate contains crown‐shaped [Sb₈]^8? Zintl anions which are analogous to S₈ rings. The presence of amide NH₂^? as an additional anion is deduced from coordination observations and the close similarity of structural features to the structure of KNH₂.     

8-Aza-7-deazaadenine N8- and N8-(β-D-2′-Deoxyribofuranosides): Building blocks for automated DNA synthesis and properties of oligodeoxyribonucleotides

Oligonucleotides with alternating 8-aza-7-deaza-2′-deoxyadenosine (= c⁷z⁸A_d2) and dT residues (see 11, 14 and 16 ) or 4-aminopyrazolo [3,4-d] pyrimidine N²-(β-D -2′-deoxyribofuranoside) (= c⁷z⁸A′_d¹); ( 3 ) and dT residues (see 12 ) have been prepared by solid-phase synthesis using P(III) chemistry, Additionally, palindromic oligomers derived from d(C-T-G-G-A-T-C-C-A-G) but containing 2 or 3 instead of dA (see 18 – 22 ) have been synthesized. Benzoylation of 2 or 3 , followed by 4,4′-dimethoxytritylation and subsequent phosphitylation yielded the methyl or the cyanoethyl phosphoramidites 8a,b and 9 . They were employed in automated. DNA synthesis. Alternating oligomers containing 2 or 3 showed increase dT_m values compared to those with dA, in particular 12 with an unusual N²-glycosylic bond. The palindromic oligomers 18 - 22 containing 2 or 3 instead of dA outside of the enzymic recognition side reduced the hydrolysis rate, replacement within d(G-A-T-C) abolished phosphodiester hydrolysis.     

[Pd8(CH3COO)8(NO)8]: solution from X‐ray powder diffraction data

The water‐insoluble title compound, octakis(μ‐acetato‐κ²O:O)­octakis(μ‐nitro­so‐κ²N:O)­octapalladium(II), [Pd₈(CH₃COO)₈(NO)₈], was precipitated as a yellow powder from a solution of palladium nitrate in nitric acid by adding acetic acid. Ab initio crystal structure determination was carried out using X‐ray powder diffraction techniques. Patterson and Fourier syntheses were used for atom locations, and the Rietveld technique was used for the final structure refinement. The crystal structure is of a molecular type. The skeleton of the [Pd₈(CH₃COO)₈(NO)₈] mol­ecule is con­structed as a tetragonal prism with Pd atoms at the vertices. The eight NO⁻ groups are in bridging positions along the horizontal edges of the prism. The N and O atoms of each nitro­so group coordinate two different Pd atoms. The vertical edges present Pd⋯Pd contacts with a short distance of 2.865 (1) Å. These Pd atoms are bridged by a pair of acetate groups in a cis orientation with respect to each other. The complex has crystallographically imposed 4/m symmetry; all C atoms of the acetate groups are on mirror planes. The unique Pd atom lies in a general position and has square‐planar coordination, consisting of three O and one N atom.     

Synthesis and X-ray structural investigation of zinc 2-methyl-8-selanylquinolinate. Comparative crystallographic analysis of the zinc 8-sulfanyl-, 8-selanyl-, and 2-methyl-8-selanylquinolinate molecules

Zinc 2-Methyl-8-selanylquinolinate Zn[C₉H₅(Me)NSe]₂ has been synthesized and its structure proved by X-ray analysis. The effect of different ligand atoms (Se or S) and a methyl group in position 2 of the ligand on the geometry of the coordinated zinc atom polyhedron has been studied for zinc 8-sulfanyl-, 8-selanyl-, and 2-methyl-8-selanylquinolinate. Dedicated to Academician E. Lukevics in recognition of his service to organometallic chemistry __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 123–128, January, 2007.     

Das neue ternäre Borid Mg8Pt4B und die neue intermetallische Verbindung PtMg2

The New Ternary Boride Mg₈Pt₄B and the New Intermetallic Compound PtMg₂ The new magnesium platinum boride Mg₈Pt₄B was obtained from a reaction of the elements in sealed niobium tubes. It crystallizes isotypically with Mg₈Rh₄B in the cubic space group with a =12.2481(1) Å and can be structurally derived from the Ti₂Ni structure type, where boron occupies cavities, which are formed by four magnesium and four platium atoms. The new intermetallic compound PtMg₂ was also prepared by reaction of the elements in a sealed Nb container and adopts the tetragonal CuAl₂ type structure, space group I4/mcm with a = 6.334(1) Å and c = 5.621(1) Å.     

Die Seltenerdmetallpolyselenide Gd8Se15, Tb8Se15−x,Dy8Se15−x,Ho8Se15−x,Er8Se15−x und Y8Se15−x (0 < x ≤ 0.3) – Zunehmende Fehlordnung in ausgedünnten,planaren Selenschichten

The Rare Earth Metal Polyselenides Gd₈Se₁₅, Tb₈Se_15?x, Dy₈Se_15?x, Ho₈Se_15?x, Er₈Se_15?x, and Y₈Se_15?x – Increasing Disorder in Defective Planar Selenium Layers Single crystals of the rare earth metal polyselenides Gd₈Se₁₅, Tb₈Se_15?x, Dy₈Se_15?x, Ho₈Se_15?x, Er₈Se_15?x, and Y₈Se_15?x (0 < x ≤ 0.3) have been prepared by chemical transport reactions (1120 K→ 970 K, 14 days, I₂ as carrier) starting from pre‐annealed powders of nominal compositions between LnSe₂ and LnSe_1.9. The isostructural title compounds adopt a 3 × 4 × 2 superstructure of the ZrSSi type and can be described in space group Amm2 with lattice parameters of a = 12.161(1) Å, b = 16.212(2) Å and c = 16.631(2) Å (Gd₈Se₁₅), a = 12.094(2) Å, b = 16.123(2) Å and c = 16.550(2) Å (Tb₈Se_15?x), a = 12.036(2) Å, b = 16.060(2) Å and c = 16.475(2) Å (Dy₈Se_15?x), a = 11.993(2) Å, b = 15.999(2) Å and c = 16.471(2) Å (Ho₈Se_15?x), a = 11.908(2) Å, b = 15.921(2) Å and c = 16.428(2) Å (Er₈Se_15?x), and a = 12.045(2) Å, b = 16.072(3) Å and c = 16.626(3) Å (Y₈Se_15?x), respectively. The structure consists of puckered [LnSe] double slabs and planar Se layers alternating along [001]. The planar Se layers contain a disordered arrangement of dimers, Se^2? and vacancies. All compounds are semiconducting and contain trivalent rare earth metals (Ln³⁺).     

A Cucurbit[8]uril 2:2 Complex with a Negative pKa Shift

A viologen derivative carrying a benzimidazole group ( V-P-I ²⁺; viologen–phenylene–imidazole V-P-I ) can be dimerized in water using cucurbit[8]uril (CB[8]) in the form of a 2:2 complex resulting in a negative shift of the guest pK_a, by more than 1 pH unit, contrasting with the positive pK_a shift usually observed for CB-based complexes. Whereas 2:2 complex protonation is unclear by NMR, silver cations have been used for probing the accessibility of the imidazole groups of the 2:2 complexes. The protonation capacity of the buried imidazole groups is reduced, suggesting that CB[8] could trigger proton release upon 2:2 complex formation. The addition of CB[8] to a solution containing V-P- I ³⁺ indeed released protons as monitored by pH-metry and visualized by a coloured indicator. This property was used to induce a host/guest swapping, accompanied by a proton transfer, between V-P-I ³⁺ ⋅ CB[7] and a CB[8] complex of 1-methyl-4-(4-pyridyl)pyridinium. The origin of this negative pK_a shift is proposed to stand in an ideal charge state, and in the position of the two pH-responsive fragments inside the two CB[8] which, alike residues engulfed in proteins, favour the deprotonated form of the guest molecules. Such proton release triggered by a recognition event is reminiscent of several biological processes and may open new avenues toward bioinspired enzyme mimics catalyzing proton transfer or chemical reactions.     

Investigation of Copper Halide:Hydrothermal Syntheses and Characterization of CuBr2(C12H8N2) and Cu3Br3(C12H8N2)2

The reaction of CuBr₂ with 1,10‐phen‐H₂O (1,10‐phen = 1,10‐phenanthroline) gave two compounds: CuBr₂(C₁₂H₈N₂) and Cu₃Br₃(C₁₂H₈N₂)₂. Their structures have been characterized by single‐crystal X‐ray diffraction analysis, elemental analyses, thermogravimetric analyses (TGA) and measurement of variable temperature magnetic susceptibility. Crystal data for CuBr₂(C₁₂‐H₈N₂): monoclinic, space group P2₁/n, a = 0.9977(3) nm, b = 0.65138(14) nm, c = 1.8207(4) nm, β = 91.624(18)°, V = 1.1828(5) nm³, Z = 2. Crystal data for Cu₃Br₃(C₁₂H₈N₂)₂: monoclinic, space group C2/c, a = 1.00167(11) nm, b = 1.4523(4) nm, c = 1.6295(3) nm, β = 94.386(14)°, V = 2.3635(8) nm³, Z = 3.     

Eine alternative Synthese des Oligoalumosiloxans [Ph2SiO]8[Al(O)OH]4 und seiner Alkohol‐Addukte

The oligoalumosiloxanes {[Ph₂SiO]₈[Al(O)OH]₄·2,5Et₂O·HOtBu} ( 6 ) and {[Ph₂SiO]₈[Al(O)OH]₄·2Et₂O·2HOiPr} ( 7 ) have been obtained from the reaction of diphenylsilanediol with aluminium‐tri‐tert‐butoxide and aluminium‐tri‐iso‐propoxide in ethyl ether with reasonable yields. In a 1:1 molar mixture of toluene and the respective alcohol (iso‐propanol or tert‐butanol), the ethyl ether molecules in {[Ph₂SiO]₈[Al(O)OH]₄·4Et₂O}, in 6 or 7 can be completely displaced forming the compounds [Ph₂SiO]₈[Al(O)OH]₄·4HOiPr ( 8 ) and [Ph₂SiO]₈[Al(O)OH]₄·nHOtBu ( 9 ). Whereas 6 , 7 and 8 are crystalline, 9 is obtained as a viscous liquid. An X‐ray structure determination on {[Ph₂SiO]₈[Al(O)OH]₄·3Et₂O·HOtBu} reveals different bonding modes of the diethyl ether molecules to the oligoalumosiloxane compared to the tert‐butanol, which forms two hydrogen bonds (one to the OH‐group of the inner Al₄(OH)₄ cycle and one through the alcohol OH‐group to a Si–O–Al moiety. The alcohol adducts have been characterized in solution through ¹H‐, ¹³C‐ and ²⁹Si‐NMR and show dynamic equilibria between the oligoalumosiloxane [Ph₂SiO]₈[Al(O)OH]₄ and the alcohol molecules.     

Preparation of a polyglycol-C8 bonded phase and its characteristics

Summary A new bonded phase containing both non-polar C₈ and polar polyglycol chains was synthesized in two steps. Silica was first silanized with octyltrimethoxysilane and then the intermediate product was reacted with tetraethylene glycol to introduce the polar group. The bonded phase exhibits a selectivity different from that of C₈ or C₁₈ reversed phases with a mixed-mode retention mechanism. The silanol effect on the polyglycol-C₈ bonded phase was examined with the test mixture proposed by Engelhardt and co-workers. The experimental results indicate that the new bonded phase displays less silanol effect. The observed tailing of some ionizable species resulted mainly from their partial dissociation at the pH values of eluents close to thepK _a values of the solutes. Some potential applications of the bonded phase are also given.     

Tuning the Adsorption Selectivity of ZIF-8 by Amorphization

Amorphous metal–organic frameworks (a_mMOFs) with a partially collapsed structure are a new category of porous hybrid materials. Here, solid-state amorphization of ZIF-8 was achieved by mechanical compression at 0.75 GPa. The compression-induced amorphous ZIF-8 (a_mZIF-8) had a collapsed structure, but retained partial porosity. Benefiting from the deformed channel, the resultant a_mZIF-8 exhibited preferable adsorption of C₃H₆, resulting in higher thermodynamic adsorption selectivity of C₃H₆/C₃H₈ (6.72) than the crystalline counterparts (1.06). Further, a_mZIF-8 achieved complete separation of an equimolar C₃H₆/C₃H₈ mixture with the first breakthrough of C₃H₈. a_mZIF-8 also displayed an enhancement in CO₂/N₂ and CO₂/CH₄ adsorption selectivities. More importantly, a self-standing a_mZIF-8 membrane with boundary-free microstructure was constructed for the first time, and exhibited separation potential for H₂/CH₄, CO₂/N₂, CO₂/CH₄, and C₃H₆/C₃H₈ with ideal selectivities of 14.79, 12.83, 16.23, and 2.67, respectively.     

Cs3UP2S8, a Coordination Polymer Containing the Unprecedented [U=S]2+ Sulfidouranium(2+) Moiety

Although terminal chalcogeno ligands are well known for the group 5 and 6 transition metals, they are highly unusual for the oxophilic group 4 metals and unknown so far for the lanthanides or actinides. Cs₃UP₂S₈, is the first actinide compound containing a terminal M=S group. It was synthesized by reacting uranium metal, Cs₂S, S, and P₂S₅ in a 4:1:8:3 ratio at 700 °C in an eutectic LiCl/CsCl mixture. The crystal structure was determined by single‐crystal X‐ray diffraction techniques. Cs₃UP₂S₈ crystallizes in the rhombohedral space group R$\bar{3}$ [a = 15.5217(8) Å; c = 35.132(2) Å, V = 8305.0(8) ų, Z = 18]. The crystal structure is based on a tetrahedral network type, wherein the uranium atoms are coordinated by a unusual sulfido moiety and thiophosphate groups in a pseudo‐tetrahedral fashion. The U=S distance of 2.635(3) Å observed in the sulfide moiety is approx. 0.2 Å shorter than the average U–S single bond length, indicating a double‐bond type character.     

Radical Arylation Reactions of 4, 6, 8-Trimethylazulene

The synthesis of 1- and 2-aryl-substituted (aryl = Ph, 4-NO₂? C₆H₄, and 4-MeO? C₆H₄) 4, 6, 8-trimethylazulenes ( 4 and 3 , respectively) in moderate yields by direct arylation of 4, 6, 8-trimethylazulene ( 8 ) with the corresponding arylhydrazines 13 in the presence of Cu^IIions in pyridine (see Scheme 4) as well as with 4-MeO? C₆H₄Pb(OAc)₃ ( 16 ) in CF₃COOH (see Scheme 5) is described. With 13 , also small amounts of 1, 2- and 1, 3-diarylated azulenes (see 14 and 15 , respectively, in Scheme 4) are formed. The 4-methoxyphenylation of 8 with 16 yielded also the 1, 1′-biazulene 17 in minor amounts (see Scheme 5). 4, 6, 8-Trimethyl-2-phenylazulene ( 3a ) was also obtained as the sole product in moderate yields by the reaction of sodium phenylclopentadienide ( 1a ) with 2, 4, 6-trimethylpyrylium tetrafluoroborate ( 2 ) in THF (Scheme 1). The attempted phenylation of 8 as well as of azulene ( 9 ) itself with N-nitroso-N-phenylacetamide ( 10 ) led only to the formation of the corresponding 1-(phenylazo)-substituted azulenes 12 and 11 , respectively (Scheme 3).     

Studies on tetraborane(8) carbonyl, B4H8·CO: its isomeric composition in the gas phase and in solution, and its reactions with alkenes

¹¹B NMR spectra of tetraborane(8) carbonyl, B₄H₈·CO 1, reveal a changeover in the distribution of isomers in going from toluene solution to the gas phase. Fortuitously the distribution is 60:40 in each case, but comparison with published electron diffraction data and ab initio/IGLO computations indicates that the CO group is disposed endo with respect to the B₄ `butterfly' framework in the predominant isomer in the gas phase, and exo in solution. The results also allow conclusions to be drawn about the geometries of other B₄H₈·L isomers on the basis of their reported proton NMR chemical shifts. Reactions of B₄H₈·CO with ethene and propene at ca. 30 bar yield products, R₄B₄H₄·CO (R=Et 2 or Pr³ 3), in which all four wingtip hydrogen atoms of the tetraborane carbonyl have been replaced by alkyl groups. Variable-temperature ¹¹B and ¹H NMR spectra of 2 and 3 reveal interesting fluxional behaviour.     

Studies On Some Transition Metal Mixed Ligands Complexes Glycinyldithiocarbamate and 8-hydroxyquinoline moiety

This paper reports the isolation and characterisation of mixed ligand complexes of the types Ba[M(Ox)₂glydtc], [M₂′(Ox)₄glydtc], [M₂(QA)₂glydtc] and [M₂′(QA)₄glydtc] (where glydtc=glycinyldithiocarbamate; HOx=8-hydroxyqinoline;HQA=p-methyl-5-phenylazo-8-hydroxyquinoline and M=Co(II),Ni(II) or Cu(II); M′=Fe(III) or Cr(III). The structures for the complexes have been elucidated on the basis of elemental analysis, electronic, IR and mass spectroscopy. Electronic spectral data for the complexes were in accordance with an octahedral environment around the central metal ions in all metal chelates except for [Co₂(QA)₂glydtc] and [Ni₂(QA)₂glydtc] where the structure around Co(II) and Ni(II) may be tetrahedral. The complexes were proposed to be dimeric except those of Ba[M(Ox)₂glydtc]. A study of the thermal decomposition of the complexes has also been carried out. For Ba[M(Ox)₂glydtc], elimination of carbon dioxide was observed. However, evolution of nitrogen and formation of tolyl radicals occur for [M₂(QA)₂glydtc] and [M₂′(QA)₄glydtc]. Kinetic parameters for the various decomposition stages were calculated using the Coats–Redfern and Horowitz–Metzgerequations. This revised version was published online in August 2006 with corrections to the Cover Date.