Synthesis of α-substituted 3-ulosonic acids from aldonolactones

Zinc-silver/graphite mediated Reformatsky-reaction of furanoid aldonolactones with α-bromo-esters allows the synthesis of α-substituted 3-ulosonic acids in high yields.     

TG and DTA investigations on hexaiodometallates

K₂ThI₆, Rb₂ThI₆, Cs₂ThI₆ and Cs₂TiI₆ could be prepared from the reactions of alkali metal iodides with ThI₄ and TiI₄. By precipitation with an excess of alkali metal iodide, Rb₂OsI₆, Cs₂OsI₆, K₂PtI₆ and Rb₂PtI₆ were obtained from acid solutions of the hexaiodometallate(IV) anions, Rb₂OsBr₆ was synthesized in a similar way from the corresponding bromine compounds.The formation of the 4th group hexaiodometallates was investigated by DTA. The thermal stability of the complex salts was determined.     

Basis set dependence,precision, and accuracy of full ab initio gradient optimizations of molecular structures of nonstrained hydrocarbons. I. CC bond lengths

Different highly accurate experimental determinations of molecular structures (ED: r_g and r⁰_α, MW: r₀, r_s, and r_z, and X-ray distances) of 14 unstrained hydrocarbons have been linearly correlated with corresponding self-consistent field Hartree Fock (SCF HF) ab initio full gradient-optimized structures. From the eight applied basis sets (STO -3G, STO -6G; 3-21G, 4-31G, 6-31G, 6-311G; 6-31G*, and 6-31G**) the 6-31G basis set, although not best regarding total energies, yields statistically the most precise regression equation, which allows the prediction of ED r_g CC distances as reliable as the best experimental determinations. Surprisingly the accuracy of all calculated CC distances (measured as difference Δ between calculated CC distances and experimental ED r_g values) depends linearly on bond distances, with the largest deviations being observed for triple bonds. This seems to be a clear indication of different influences of correlation effects on calculated geometries which are neglected in the applied HF treatment. The linear regression equations presented here allow the prediction of any kind of experimental CC distance parameters for each of the eight basis sets considered. Even experimentally unknown r_e CC distances may be predicted from these single determinantal HF optimizations.     

Realizations of Frobenius Functions

In an earlier paper (Ágoston et al.,CMS Conf. Proc.18(1996), 17–37) we studied the so-called Frobenius functions on certain translation quivers. Here we show that the classification given there is in some sense complete: every Frobenius length function on the wingW(n) and the tubeT(n) is equivalent to the length function on a convex subquiver of the Auslander–Reiten quiver of the module category over some algebraA.     

A quantum chemistry study of the Cl atom reaction with formaldehyde

The elementary vapor-phase reaction between Cl atoms and HCHO has been studied by ab initio methods. Calculations at the MP2, MP3, MP4(SDTQ), CCSD, CCSD(T), and MRD-CI levels of theory show that the reaction is characterized by a low electronic barrier; excluding the effects of spin-orbit splitting in Cl, our best estimate at the MRD-CI/aug-cc-pVTZ//RHF-RCCSD(T)/aug-cc-pVTZ level of theory predicts a Born-Oppenheimer barrier height of 0.7 kJ mol-1. The energies of the lowest six electronic states as resulting from MRD-CI calculations are presented at discrete points along the reaction path, and two avoided crossings are found in the transition state region. The spin-orbit splitting in Cl is also calculated along the reaction path; it is not negligible in the transition state region and is found to increase the barrier by only 1.4 kJ mol-1 at the RCCSD(T)/aug-cc-pVTZ transition state geometry. The minimum energy path of the reaction connects an energetically weakly stabilized adduct on the flat potential surface on the reactant side and an energetically strongly stabilized postreaction adduct. The reaction rate coefficient and the kinetic isotope effects were calculated using improved canonical variational theory with small curvature tunneling (ICVT/SCT), and the results were compared to experimental data. The experimental reaction rate coefficient is reproduced within its uncertainty limits by variational transition state theory with interpolated single-point energy corrections (ISPE) at the MP4(SDTQ) level of theory and by conventional transition state theory with interpolated optimized energies (IOE) at the MRD-CI//RCCSD(T) level of theory and interpolated optimized geometries at the RCCSD(T) level of theory on an MP2/aug-cc-pVTZ potential energy surface when employing scaled vibrational frequencies.     

The self-injective cluster-tilted algebras

We are going to determine the self-injective cluster-tilted algebras. All are of finite representation type and special biserial. There are two different classes. The first class are the self-injective serial (or Nakayama) algebras with n ≥ 3 simple modules and Loewy length n–1. The second class of algebras has an even number 2m of simple modules; m indecomposable projective modules have length 3, the remaining m have length m + 1. Received: 28 May 2007     

Ge−Fe Carbonyl Cluster Compounds: Ionic Liquids-Based Synthesis,Structures, and Properties

Nine Ge−Fe carbonyl cluster compounds are prepared via ionic liquids-based synthesis. This includes the novel compounds [EMIm][Fe(CO)₃I(GeI₃)], [EHIm][Fe(CO)₃I(GeI₃)], [BMIm][GeI₂{Fe(CO)₄}₂(μ-I)][AlCl₄]₂, [GeI₂{Fe(CO)₄}₂(μ-I)][Fe(AlBr₄)₃], [BMIm]₂[(FeI₂)_0.75{Fe(CO)₂I(GeI₃)₂}₂], and [EHIm][Fe(CO)₄(GeI₂)₂Fe(CO)₃GeI₃] as well as the previously reported compounds (Fe(CO)₄(GeI₃)₂, FeI₄{GeI₃Fe(CO)₃}₂, and Ge₁₂{Fe(CO)₃}₈(μ-I)₄ (EMIm: 1-ethyl-3-methylimidazolium, EHIm: 1-ethylimidazolium, BMIm: 1-butyl-3-methylimidazolium). With this series of compounds, a comparison of synthesis conditions and structural features is possible and, for instance, allows correlating the composition and structure of the respective Ge−Fe carbonyl cluster compounds with the type and acidity of the ionic liquid. With [EMIm][{GeI₃}₂Fe(CO)₃I], moreover, we can exemplarily show the thermal decomposition as a single-source precursor in the ionic liquid, resulting in bimetallic Ge−Fe nanoparticles with small size and narrow size distribution (7.0±1.4 nm).