Synthesis, structural characterization and electrochemistry of C,N-chelated organotin(IV) dicarboxylates with ferrocenyl substituents

A set of C,N-chelated organotin(IV) ferrocenecarboxylates, [L^CN(n-Bu)Sn(O₂CFc)₂] (1), [(L^CN)₂Sn(O₂CFc)₂] (2), [L^CN(n-Bu)Sn(O₂CCH₂Fc)₂] (3), [L^CN(n-Bu)Sn(O₂CCH₂CH₂Fc)₂] (4), [L^CN(n-Bu)Sn(O₂CCHCHFc)₂] (5), [L^CN(n-Bu)Sn(O₂CfcPPh₂)₂] (6), [(L^CN)₂Sn(O₂CfcPPh₂)₂] (7), and [L^CN(n-Bu)₂Sn(O₂CFc)] (8) (L^CN = 2-(N,N-dimethylaminomethyl)phenyl, Fc = ferrocenyl and fc = ferrocene-1,1′-diyl) has been synthesized by metathesis of the respective organotin(IV) halides and carboxylate potassium salts and characterized by multinuclear NMR and IR spectroscopy. The spectral data indicated that the tin atoms in diorganotin(IV) dicarboxylates bearing one C,N-chelating ligand (1 and 3-6) are seven-coordinated with a distorted pentagonal bipyramidal environment around the tin constituted by the n-butyl group, the chelating L^CN ligand and bidentate carboxylate. Compounds 2 and 7 possessing two chelating L^CN ligands comprise octahedrally coordinated tin atoms and monodentate carboxylate donors, whereas compound 8 assumes a distorted trigonal bipyramidal geometry around tin with the carboxylate binding in unidentate fashion. The solid state structures determined for 1⋅C₆D₆ and 2 by single-crystal X-ray diffraction analysis are in agreement with spectroscopic data. Compounds 1, 3-5, and 8 were further studied by electrochemical methods. Whereas the oxidations of ferrocene units in bis(carboxylate) 2 and monocarboxylate 8 proceed in single steps, compound 1 undergoes two closely spaced one-electron redox waves due to two independently oxidized ferrocenyl groups. The spaced analogues of 2, compounds 3-5, again display only single waves corresponding to two-electron exchanged.     

Optimierung der quantitativen röntgenographischen Phasenanalyse

A new procedure for an absolute quantitative X-ray phase analysis is presented, based on the square programming guaranting optimum analytical results. Theoretical conclusions are illustrated by a practical example.     

Matrices related to interpolatory quadratures

Summary An explicit formula for the coefficients of interpolatory quadratures with knots of arbitrary multiplicity which uses the eigenvectors and principal vectors of certain matrices is derived. The construction and properties of such matrices are discussed, and applications for the evaluation of Gauss and generalized Gauss-Lobatto quadratures are indicated.     

A mathematical model of realistic constitutional chemistry. A synthon approach. I: An algebraic model of a synthon

A mathematical model of a synthon is suggested. The synthon is modelled by a special so-calledS-matrix. The notion of isomeric synthons on the set of atoms A and that of a Family of Isomeric SynthonsFIS (A) is introduced. The chemical reaction is represented by a matrix equation and it is modelled by the so-calledSR-matrix. The notion of the reaction distance (RD) between two isomeric synthons is defined. A mathematical theory of the S andSR-matrices is developed.     

Spectroscopic measurements in nitrogen arcs with respect to local thermodynamic equilibrium

A wall-stabilized nitrogen arc at atmospheric pressure was studied spectroscopically in the current range from 20 to 70 A with the aim of detecting departures from LTE. Measurements of the relative intensity of several N(I) lines showed that the populations of the upper excited states are in equilibrium for currents greater than approx. 25 A. Comparisons of the excitation temperatures obtained from relative intensities with the electron temperature and with the temperature curves calculated for different departures from LTE show that deviations from equilibrium are small at the arc center for electron densities above approx. 4 × 10¹⁶ cm^-3. Deviations between the radial profiles of the electron and excitation temperatures were observed for currents between 35 and 55 A.     

New analytical method for determination and speciation of forms of carbon

A new analytical method is presented, allowing the identification and determination of various forms of carbon (elemental and combined) present in materials. The method is based on temperature-controlled heating of the sample in oxygen or an inert atmosphere, with continuous recording of the amount of carbon oxides evolved, as a function of temperature. The application of the method is demonstrated with typical examples (cast iron, artificial diamond, carbides isolated from steel, electrographite).     

NMR study of the structure of poly(N-benzoyl-8-octanelactam)

The structure of a polymer prepared by the polymerization of N-benzoyl-8-octanelactam initiated with benzoic acid was studied by ¹H and ¹³C NMR, using S-INEPT, COSY, COLOC, and ROSEY methods, with the aid of model oligomers. Beside the expected N-benzoylated segments, the polymer also contained deacylated segments and about 50% of branching units. The polymer can be characterized as a statistical, highly branched copolymer of N-benzoyl-8-octanelactam and 8-octanelactam. © 1993 John Wiley & Sons, Inc.     

Theoretical investigation of the interaction between the hydrogen atom and Pd clusters

The chemisorption of hydrogen on small Pd_n clusters (n = 1–3) has been investigated using the pseudopotential procedure followed by configuration interaction (PP-CI). The interaction of H with the cluster modeling the three-fold hollow site of the Pd(111) surface is found to be stronger than that at the bridge and the top site models. When H occupies a top site the bonding has a partial ionic character as a consequence of charge transfer from the metal to H. At the bridge and hollow sites the bonding is essentially covalent. The MO energy spectrum of the Pd₃-H (hollow) cluster is characterized by the presence of a well separated MO level ～ 7 eV below the Fermi level which is consistent with the experimentally observed photoelectron spectra of H on Pd(111) surface. The bonding between H and Pd clusters occurs mainly via d-orbitals and seems to be of quite local nature.