The effect of Fe and Ru substitution on the superconductivity in MgCNi3

We report the effects of partial substitutions of the VIIIa elements: Fe (3d) and Ru (4d) in the intermetallic perovskite superconductor MgCNi₃. In both the MgCNi_3−xRu_x and MgCNi_3−xFe_x systems, the superconducting critical temperature (T_C) decreases monotonically as x is increased. T_C decreases more slowly in the case of Ru, suggesting that the 3d electrons in Fe are magnetically pair breaking. This is supported by the normal state magnetic susceptibility measurements (χ), which shows that χ increases with Fe and decreases with Ru doping. No ferromagnetism is observed in either system.     

Acetoxyphenylketene. Reaction with biacetyl

The generation of acetoxyphenylketene (4) in the cold in the presence of biacetyl yields the single β-lactone $\text{12B}$, which undergoes a novel rearrangement to the tricyclic orthoester lactone $\text{11}$ above 130°.     

Synthesis and Properties of Bis(2,5-dimethylpyrrolo[3,4-d])tetrathiafulvalenes, a Class of Annelated Tetrathiafulvalene Derivatives with Excellent Electron Donor Properties

The synthesis of the first derivatives of bis(pyrrolo[3,4-d])tetrathiafulvalene has been studied in detail. Starting from the readily available 2,5-dimethylpyrrole (11) and N-phenyl-2,5-dimethylpyrrole, bis(2,5-dimethylpyrrolo[3,4-d])tetrathiafulvalene (8) and the N,N'-disubstituted derivatives 6, 7, 9, and 10 were prepared in good yields by practical procedures. In contrast to the other types of aromatic annelated tetrathiafulvalenes (TTFs), which have appreciably higher oxidation potentials than TTF, the redox behavior of the pyrrolo tetrathiafulvalenes (TTFs) is very close to that of TTF itself. The potential of pyrrolotetrathiafulvalenes as a new series of organic metal building blocks is shown by the two-probe conductivities of the tetracyanoquinodimethane (TCNQ) complexes of the N-phenyl compound 7 and the N-methyl compound 9, which give higher values than TTF-TCNQ under similar conditions.     

Condensed thiophenes and selenophenes: thionyl chloride and selenium oxychloride as sulfur and selenium transfer reagents

3,4-Cyanomethyl substituted thiophenes reacted with thionyl chloride in the presence of base to give dicyano substituted thieno(3,4-c)thiophenes. The use of selenium oxychloride furnished the corresponding cyano substituted seleno(3,4-c)thiophene. 1,2-Phenylenediacetonitriles gave the corresponding cyano substituted benzo(c)thiophenes and benzo(c)selenenophenes, respectively, upon reaction with thionyl chloride and selenium oxychloride in the presence of base.