1-Alkoxy-2-azaallenyl-komplexe von chrom und wolfram

The successive reaction of (CO)₆M with Na[NCR₂¹] and [Et₃O]BF₄ yields (CO)₅M[C(NCR₂¹)OEt] (II: M = Cr; III: M = W; CR₂¹ = C(C₆H₄Br-p)₂ (a), CPh₂ (b), C(C₆H₄OMe-p)₂ (c), C(C₆H₄)₂O (d), CBu₂^tt (e)). Hexacarbonyltungsten, (CO)₆W, reacts with Na[NCPh₂] and MeOSO₂F to give (CO)₅W[C(NCPh₂) OMe] (IV). X-Ray analysis of IIe shows that: (1) the CNC fragment is almost linear (171.7°); (2) the two NC bond lengths are equal within experimental error; and (3) the O,C,Cr,N plane is perpendicular to the C(Me₃),C,N,C(Me₃) plane (90.0°). Therefore compounds II–IV are best described as 1-alkoxy-2-azaallenyl complexes.     

Zur struktur von CaPdF4, CdPdF4, HgPdF4 und HpPdF2

Single crystals of CaPdF₄ (purple) and CdPdF₄ (dark blue) have been obtained by heating CaF₂ (CdF₂) with PdF₂ at 820°C (900°C) for ca. 20–30 d in sealed Pd (Pt) tubes. CaPdF₄ crystallizes tetragonal (KBrF₄-Type) with a = 5.52₁, c = 10.57₀ Å (space group I4/mcm ? D^18_4h, No. 140) Z = 4, 283 unique reflexions, R = 0.083; R_w = 0.079, CdPdF₄ cubic (CaF₂-variant) with a = 5.40₃ Å (space group Pa3 ? T^6_h, No. 205) Z = 4, 165 unique reflexions, R = 0.047, R_w = 0.032. The high pressure modification of PdF₂, obtained by heating PdF₂ in closed Pt-tubes under a pressure of ≈ 60 kbar and ‘HgPdF₄’, both black, a = 5.32₇ Å and a = 5.43 Å are isotypic. CaPdF₄ is diamagnetic, CdPdF₄ and HPPdF₂ are antiferromegnetic.     

Synthese neuer N-Vinylpyrrole

Syntheses of New N-Vinylpyrroles The reactions of pyrrolyl potassium ( 1 ) with (ethoxymethylene)malonic acid derivatives 2a–e yielded the carbanions 3a–e , which could be hydrolyzed to 4a–e , but with the exception of 4b they were not isolated, because a transformation to the N-vinylpyrroles 5a , c–e by elimination of ethanol took place; 1 reacted with 2b at 80°C to give 4b and 6 . Hydrolysis of 4b with KOH yielded 4g , which eliminated 1 mol of ethanol to form 5f , decarboxylation of which led to N-vinylpyrrole 7 . By cyclization of 5e under various conditions the pyrrolizines 8a , b are obtained, the hydrolysis of which did not give ketone 9 but only amino alcohol 10 . Some other cyclizations of 11a–c and 13 yielded the 3H-pyrrolizine derivatives 12a–c and 14 , respectively.     

Wave mechanics - the first fifty years : edited by W.C. Price,S.S. Chissick and T. Ravensdale,Butterworths, London, 1973, pp. 435, price £12.00

The free NH₃ molecule and the [Zn(NH₃)₄]²⁺ ion were studied by the kinematic coupling approach. The pure effects of this coupling were found to be small, and some modifications had to be introduced in order to get a reasonable force field. The force constants deduced for the skeletal vibrations are comparable with those of a quasi-exact force field. Calculated frequencies for [⁶⁸Zn(NH₃)₄]²⁺ and [⁶⁴Zn(ND₃)₄]²⁺ are reported in addition to those of [⁶⁴Zn(NH₃)₄]²⁺. Mean amplitudes of vibration for [⁶⁴Zn(NH₃)₄]²⁺ are given.     

Is laser-ablation-ICP-MS an alternative to solution analysis of solid samples?

The basic obstacles for the general use of laser-ablation(LA)-ICP-MS in analytical laboratories are connected with its reproducibility and calibration. A mathematical relation deduced from the correlation function of the analytical signals allows the estimation of the number of craters needed for representative analyses. The procedure was applied to different samples such as manganese crusts and soils. The ion intensities of the major elements in the manganese crusts and nodules were used as internal standards, improving relative standard deviations by factors between 2 and 3. Selected samples of wood and manganese crusts were analyzed by LA-ICP-MS and the results compared with those obtained by solution ICP-MS. The agreement of the values is within the 95% confidence limits. Powdered reference materials and, in the case of wood analysis, cellulose doped with standard solutions were used for the calibration.     

The electronic structure of benzvalene : Photoelectronspectroscopic studies

The photoelectron(PE)spectrum of tricyclo[3.1.0.0^2,6] hex-2-ene(benzvalene 1) has been recorded. The first four bands in the PE spectrum of 1 can be assigned to transitions to ²B₂, ²A₁, ²A₂ and ²B₁ states of 1¹. This assignment is discussed in terms of the results of semiempirical and ab initio calculations on 1. Furthermore the highest occupied MO's of 1 are derived qualitatively from an interaction diagram between a distorted bicyclobutane and an ethylene moiety.     

Activation analysis with fast neutrons using a cyclotron

A systematic study of activation analysis with cyclotron-produced neutrons for (n, 2n), (n, p) and (n, α) reactions is presented. The limits of detection for elements of atomic number from 6 to 80 are given. The possibilities of optimization of irradiation conditions by the choice of the most suitable neutron spectrum are discussed. The potential of this fast neutron activation analysis method is compared with that of 14 MeV neutron activation analysis.     

Darstellung und Struktur von Pyrazolyl-Kationen mit Polymethin- und Methan-Gerüst

The 4-pyrazoline-3-one1 reacts with 4-dimethylaminobenzaldehyde to yield the stable asymmetric cyanine dye2b which reacts with1 to give the colorless (aryl) (dipyrazolyl) methane3b. Using aldehydes with less cationstabilizing groups the polymethines2 are not isolated but only the methanes3. The structures of2b and3 are discussed by¹ H,¹³C and Hetero NMR spectra.     

Schwingungsspektren und Normalkoordinatenanalyse einiger Methyl-und Trimethylsilyl-hydroxylamine

Zusammenfassung Die Infrarot-und Raman-Spektren folgender Hydroxylamin-Derivate wurden registriert und zugeordnet: (CH₃)₃SiONH₂ (1), (CH₃)₃SiONHSi(CH₃)₃, (CH₃)₃SiON[Si(CH₃)₃]₂ (3), CH₃ONH₂ (4), CH₃ON[Si(CH₃)₃]₂ (5), CH₃NHOCH₃, CH₃N[Si(CH₃)₃]OCH₃, (C₂H₅)₂NOH und (C₂H₅)₂NOSi(CH₃)₃. Eine Normalkoordinatenanalyse für NH₂OH,1, 3, 4 und5 zeigt, daß sich die Spektren durch Übertragung gleichbleibender Kraftkonstanten der Molekülfragmente wiedergeben lassen. O-und N-Substituenten beeinflussen die NO-Kraftkonstante nicht; die SiO-und SiN-Valenzkraftkonstanten sind mit 3,3 mdyn/Å bemerkenswert niedrig.

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Vibrational spectra and normal coordinate analysis of some methyl-and trimethylsilylhydroxylamines

The infrared and Raman spectra of the hydroxylamine derivatives quoted above were recorded and frequencies assigned. A normal coordinate treatment of NH₂OH,1, 3, 4 and5 showed that the spectra can be explained by a single force field set up by transferring force constants from the different fragments of the molecules. The NO stretching force constant remains unaffected by different substituents. The SiO and SiN stretching force constants are remarkably small (c. 3.3 mdyn/Å).

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Mit 4 Abbildungen     

Electrochemical behaviour of mono- and oligonucleotides I. Effects of charge and configuration of adenine mononucleotides on their adsorption at the mercury—solution interface

A systematic study of the adsorption and interfacial behaviour of the adenine mono-nucleotides (5′-AMP, 3′-AMP, cyclic 3′,5′-AMP, 5′-ADP and 5′-ATP) and adenosine for comparison at the HMDE has been carried out at pH 3.4 to 3.5. Thus, the N(1) of the adenine moiety is protonated to a major extent.The adsorption was followed by single sweep voltammetry (measurement of the time integral of the reduction peak of the adsorbed adenine moiety) and by a.c. voltammetry (out-of-phase component of the a.c. response being proportional to the differential double layer capacity). In this paper the situation corresponding to a “dilute” adsorption layer existing at low bulk concentrations is studied for various degrees of coverage. The potential dependence of the coverage is of bell shaped type with an extended maximum region around the potential of electrocapillary maximum (E_ecm) of the blank. For the same bulk concentration the coverage decreases in the series AMP, ADP, ATP, i.e. with increasing negative charge of the nucleotide, and at the same time the potential range of adsorption narrows. Among the monophosphates the coverage decreases in the series 3′-AMP, 5′-AMP, cyclic 3′,5′-AMP. The variations are connected with the varying charge of the mononucleotides and with the possibilities for interactions with adjacent molecules in the adsorption layer.At elevated bulk concentrations above a threshold value a substantial increase in coverage occurs around E_ecm as due to strong interactions between the adsorbed base moieties a rather compact film is formed.