Übergangsmetall—methylen-komplexe: XLVIII. Addition und ringschluss bei reaktionen von α-ketodiazoalkanen mit metall—metall-doppelbindungen der metallcarbonyl-reihe: Aufbau metallacyclischer strukturen

The α-diazoketones 2a–h,k,l react with the dinuclear organorhodium complex 1 with elimination of dinitrogen and concomitant addition of their carbonyl-flanked carbene moieties upon the metal—metal double bond. The μ-alkylidene complexes 3f–h thus accessible, represent the final products; the trimethylsilyl derivative 3i was synthesized for comparison. By contrast, the derivatives 3a–e,l behave rather as IR-spectroscopically identified intermediates that, at room temperature, undergo rapid consecutive intramolecular cycloaddition reactions yielding the novel compounds 4a–e and 5l, respectively. Formation of 4a–e results from nucleophilic attack of the keto groups of the bridging ligands upon one of the metal carbonyl units. This type of cyclization process comprises the construction of a new oxygen—carbon bond. The metallacyclic structures thus obtained have been elucidated in the cases of 4c and 4e by means of single crystal X-ray diffraction techniques and no longer obey the structural criteria of type-3 μ-alkylidene complexes. An internal experiment concurrently carried out by use of the diazoalkane 2e furnished proof that the cyclization process occurred regiospecifically: only the more nucleophilic keto-oxygen atom is subject to ring closure, whereas the oxygen atom of the ester carbonyl group does not participate in this reaction. The bis(acyl)methylene derivatives 3f–h resist cyclization and retain their structures even at elevated temperatures (cf. boiling tetrahydrofuran). The carbocyclic diazo precursor 2k (diazodimedone) requires more drastic conditions (boiling benzene) for the reaction with compound 1 to occur; here, the cycloadduct 5k is formed following nitrogen elimination. According to a single crystal X-ray diffraction study, the ketocarbene fragment derived from 2k has been added across the dinuclear metalcarbonyl core, finally acting as a bridging structural unit. In contrast to the cycloadducts 4a–e, a new carbon—carbon bond is formed during the synthesis of 5k. The dimetallacycle 5l results from a two-step cyclo-elimination between the bisdiazoalkane 2l and the organorhodium compound 1.     

A new solution of Schmutzer's projective relativistic cosmology

Schmutzer's cosmological model on the basis of his projective unified field theory leads to a system of differential equations equivalent to a set of highly complicated Abel differential equations [1, 2]. This paper is concerned with the properties of this coupled system of differential equations. The main results of this paper are as follows, (i) We have found the explicit general solution of the cosmological equations for the case=±5/2,= ±1. (ii) The procedure of solving the general case arbitrary=0 is easily within this formalism, (iii) After having found the solution with arbitrary,=±1, one gets the corresponding solution= -, =±1. (iv) In general the coupled system of differential equations describing Schmutzer's cosmological model is equivalent to a single generalized Emden differential equation and it is identical to Emden's differential equation for special values of the parameter.     

Zur Kenntnis von BiBr und BiBr1,167

On BiBr and BiBr_1,167 Preparation and crystal structures of BiBr_1,167 and BiBr are describe as well as their phase relationships. BiBr_1,167 is isotypic with the familiar BiCl_1,167, the structures comprising the cluster Bi with the same Bi? Bi distances and deviations from trigonal symmetry. A simple electrostatic attraction-repulsion calculation with respect to the stability of the particular cluster configuration is given. The structure of BiBr consists of infinite onedimensional chains [Bi₄Br₄] as the structure of BiI. These compounds are structurally classified as special stacking variants of a common motif.     

Über die Wanderung der Carboxylatgruppe bei der Benzilsäureumlagerung. 26. Mitteilung über Reduktone und Tricarbonylverbindungen

The benzilic acid rearrangement of ethyl α,β-dioxo-butyrate was studied by NMR.-and UV.-techniques. In weak alkaline media (pH < 10) the ester group is hydrolyzed first, then the carboxylate group migrates to form methyltartronate. The migration of the carboxylate group was proved by radioactive labeling. At higher pH-values (pH > 11,5) the intakt ester group migrates, with ester hydrolysis occuring as a second step.     

Hexacyanoferrate-based composite ion-sensitive electrodes for voltammetry

Composite electrodes made of graphite, paraffin and metal hexacyanoferrates exhibit a voltammetric response of the hexacyanoferrate ions, the potential of which depends linearly on the logarithm of concentration of alkali and alkaline-earth metal ions. This behaviour has been observed on account of the fact that the electrochemical reaction is accompanied by an exchange of these ions between the solution and the zeolitic lattice of the hexacyanoferrates for charge compensation. The voltammetric determination of the formal potential of these electrodes in a solution allows the quantitative analysis of the ions which are exchanged between the metal hexacyanoferrates and the aqueous solutions. Iron(III), copper(II), silver(I), nickel(II) and cadmium(II) hexacyanoferrates have been studied for the determination of H(+), Li(+), Na(+), K(+), Rb(+), Cs(+), NH(+)(4), Mg(2+), Ca(2+) and Ba(2+). In some cases, the selectivity constants are as low as 3.10(-4), or even so small that their exact value is inaccessible. Electrodes made of iron (III), copper (II), silver (I), nickel (II) and cadmium (II) hexacyanoferrates are most suitable for the determination of potassium ions. Electrodes with nickel (II) and cadmium (II) hexacyanoferrates are also suitable for the determination of caesium ions. The working range of the electrodes also depends on the conductivity of the solutions and can range from 10(-5) to 1 mol l(-1). Typical standard deviations of the potential measurements are 3 mV.