The electronic structure of bis(o-phenylenediamido)nickel,Ni[C6H4(NH)2]2

Extended Hückel and multiple scattering Xα calculations are reported for the title complex. Both sets of results are in quantitative agreement, suggesting that part of the unusual spectral and electrochemical properties of this system may be ascribed to the predominantly ligand character of the HOMO and LUMO orbitals.     

The electronic structure of Cu(ethanediimine)+2

Extended-Hückel and multiple-scattering Xα molecular orbital calculations are reported for the Cu(ethanediimine)⁺₂ complex. The results obtained are in agreement. From the calculated electronic transition energies, it is inferred that the lowest excited state is a B₂ state of metal-to-ligand charge-transfer type, confirming resonance Raman results.     

Pyrolysis of a mixture of n-alkanes (chiefly C12-C18) atCA. 1053 K: Kinetic study

The thermal decomposition of a mixtures of n-alkanes, chiefly C₁₂-C₁₈ (commercial name Solpar) in the presence of steam (steam cracking) was studied in a plug flow reactor at ca. 1053 K. The tubular reactors were wound Incoloy steel tubes (I.D. 4 nm), heated by high-frequency induction. The total pressure in the reactor was slightly above atmospheric.The thermal decomposition mechanism of n-tetradecane, the major alkane in the Solpar mixture, allows the identification of all the primary products (non-zero initial rate of formation) by gas chromatography. Under these experimental conditions, very close to those of industrial stream cracking, secondary products (zero initial rate of formation) were observed and were qualitatively interpreted from elementary steps including the main primary products. This kinetic study also stresses the importance of the new steam cracking reactors calles “millisecond furnaces”, since these reactors produce high yields of light olefins and low yields of monoaromatic hydrocarbons.     

Nickel-mediated hydrogenolysis of C-O bonds of aryl ethers: what is the source of the hydrogen?

Mechanistic studies of the hydrogenolysis of aryl ethers by nickel were undertaken with (diphosphine)aryl methyl ethers. A Ni(0) complex containing Ni-arene interactions adjacent to the aryl-O bond was isolated. Heating led to aryl-O bond activation and generation of a nickel aryl methoxide complex. Formal β-H elimination from this species produced a nickel aryl hydride which can undergo reductive elimination in the presence of formaldehyde to generate a carbon monoxide adduct of Ni(0). The reported complexes map out a plausible mechanism of aryl ether hydrogenolysis catalyzed by nickel. Investigations of a previously reported catalytic system using isotopically labeled substrates are consistent with the mechanism proposed in the stoichiometric system, involving β-H elimination from a nickel alkoxide rather than cleavage of the Ni-O bond by H(2).     

A curved ultrasonic actuator optimized for spherical motors: Design and experiments

Multi-degree-of-freedom angular actuators are commonly used in numerous mechatronic areas such as omnidirectional robots, robot articulations or inertially stabilized platforms. The conventional method to design these devices consists in placing multiple actuators in parallel or series using gimbals which are bulky and difficult to miniaturize. Motors using a spherical rotor are interesting for miniature multidegree-of-freedom actuators. In this paper, a new actuator is proposed. It is based on a curved piezoelectric element which has its inner contact surface adapted to the diameter of the rotor. This adaptation allows to build spherical motors with a fully constrained rotor and without a need for additional guiding system. The work presents a design methodology based on modal finite element analysis. A methodology for mode selection is proposed and a sensitivity analysis of the final geometry to uncertainties and added masses is discussed. Finally, experimental results that validate the actuator concept on a single degree-of-freedom ultrasonic motor set-up are presented.     

Mass spectra of liquid crystals. V.—cyclohexyl and phenyl esters of cyclohexanecarboxylic and benzole acids

The 70 eV electron impact mass spectra of 38 cyclohexanecarboxylate and 15 benzoate derivatives are presented. This part includes data on six substituted cyclohexyl and 47 derivated phenyl esters, including eleven alkoxyphenyl and 17 dicyanoalkoxypnenyl esters. Based on the observed peak shifts by various substituents, the elemental formulae of the main fragment ions are rationalized.