Effect of included guest molecules on the normal state conductivity and superconductivity of beta''-(ET)(4)[(H(3)O)Ga(C(2)O(4))(3)].G (G = pyridine,nitrobenzene)

Normal state conductivity and superconductivity together with bulk magnetic susceptibility and magnetization measurements have been measured for two molecular charge-transfer salts: beta' '-(ET)4[(H3O)Ga(C2O4)3]G (ET = bis(ethylenedithio)tetrathiafulvalene, G = pyridine for compound I and nitrobenzene for compound II). With the exception of the included guest molecules (G) the crystal structures are almost identical. Both show minima in their electrical transport at 130 K for I and at 160 K for II, but at lower temperatures their behaviors differ markedly. The resistance of I reaches a maximum at 50 K with a further small peak at 2 K and possible superconductivity only below 2 K, whereas that of II increases continuously down to 7.5 K, where an abrupt transition to a superconducting state occurs.     

Picrylamino-substituted heterocycles. VI. Pyrimidines

The condensation of various aminopyrimidines with picryl chloride and picryl fluoride has been investigated as part of our continuing effort in the field of picrylamino-substituted heterocycles. Most of the aminopyrimidines that can tautomerize reacted with picryl fluoride to form picryl derivatives of their imino forms, but they gave picrylamino derivatives when they condensed with picryl chloride.     

X-ray structure of fac-[RuH(1,5-cod)(NH2NMe2)3][PF6]: Stabilization of coordinated substituted hydrazines by hydrogen bonding

The structure of [RuH(cod)(NH₂NMe₂)₃][PF₆] has been solved by X-ray diffraction methods and shows the cation to contain a facial arrangement of N,N-dimethylhydrazine ligands, coordinated via the NH₂ nitrogen atoms, and held together by hydrogen bonds.     

13C and 2H kinetic isotope effects and the mechanism of bromination of 1-pentene under synthetic conditions

[formula: see text] The 13C and 2H kinetic isotope effects for the bromination of 1-pentene with Br2 in CCl4 were determined and interpreted with the aid of calculationally predicted isotope effects. The isotope effects observed are consistent with rate-limiting bromonium ion formation and do not fit with either rate-limiting production of a pi complex or reaction of a reversibly formed bromonium ion. This rules out some of the mechanistic complexities suggested for other brominations, though the identity of the brominating reagent(s) under these synthetic conditions remains uncertain.     

Carbometalations of simple alkenes with allyldibromoborane

[formula: see text] The allylboration of alkenes with allyldibromoborane is described. Utilizing an improved methodology for the synthesis of allyldibromoborane, 1,3-dienes, styrene, and even isolated alkenes could be carbometalated in high yield regio- and stereospecifically at 0 degree C. This high reactivity of allyldibromoborane significantly expands the scope of carbometalations of alkenes.     

Aromatic foldamers as scaffolds for metal second coordination sphere design

As metalloproteins exemplify, the chemical and physical properties of metal centers depend not only on their first but also on their second coordination sphere. Installing arrays of functional groups around the first coordination sphere of synthetic metal complexes is thus highly desirable, but it remains a challenging objective. Here we introduce a novel approach to produce tailored second coordination spheres. We used bioinspired artificial architectures based on aromatic oligoamide foldamers to construct a rigid, modular and well-defined environment around a metal complex. Specifically, aza-aromatic monomers having a tethered [2Fe–2S] cluster have been synthesized and incorporated in conical helical foldamer sequences. Exploiting the modularity and predictability of aromatic oligoamide structures allowed for the straightforward design of a conical architecture able to sequester the metal complex in a confined environment. Even though no direct metal complex–foldamer interactions were purposely designed in this first generation model, crystallography, NMR and IR spectroscopy concurred to show that the aromatic oligoamide backbone alters the structure and fluxional processes of the metal cluster.

Wrapping a [2Fe–2S] metal complex in an aromatic foldamer helix is introduced as a new approach to tailor a second coordination sphere.