Minimalist peptidomimetic cyclophanes as strong organogelators

L-Valine containing cyclophanes have been shown to gelate organic solvents leading to soft materials with a clear expression of their chirality at the supramolecular level.     

New supported beta-amino alcohols as efficient catalysts for the enantioselective addition of diethylzinc to benzaldehyde under flow conditions

[formula: see text] Polymeric monoliths 10 containing an amino alcohol moiety derived from an industrial waste material represent one of the best ligands for the enantioselective catalytic addition of ZnEt2 to benzaldehyde (99% ee), being recoverable and usable under flow conditions.     

Efficient immobilisation of Rh-MonoPhos on the aluminosilicate AlTUD-1

Rhodium-MonoPhos was successfully immobilised by ionic interactions on aluminosilicate AlTUD-1. The resulting new heterogeneous catalyst can be used in water and showed excellent enantioselectivity and activity in the asymmetric hydrogenation of methyl-2-acetamidoacrylate.     

Alkaline side-coordination strategy for the design of nickel(II) and nickel(III) bis(1,2-diselenolene) complex based materials

The deprotonated form of the pyrazine-2,3-diselenol (pds) ligand, pds(2-), reacts with Ni(II) inorganic salts to form the nickel compounds [Ni(II)(pds)(2)](nBu(4)N)(2) (1), [Ni(II)(pds)(2)]Na(2).2H(2)O (2), and [Ni(III)(pds)(2)](2)Na(2).4H(2)O (3), depending on the reaction conditions. They are characterized by NMR, EPR, UV-vis, and IR spectroscopies, elemental analysis, cyclic voltammetry, and X-ray crystallography. The crystal structure of compound 3 shows the formation of segregated stacks of Ni(pds)(2-) units, with a strong dimerization along the stacks. The stacked fashion of the crystal packing was expected since the supramolecular forces of the alkaline side coordination to the pyrazine moieties dominate, as happens in the recently reported analogous copper system [Cu(III)(pds)(2)]Na.2H(2)O. The structure of 2 further emphasizes the alkaline coordination as the dominating supramolecular event, and an orthogonal array of 2D layers is observed. The absence of alkaline cations in complex 1 is reflected in a crystal packing with isolated complex Ni(pds)(2)(2-) units. The dimerization found in the paramagnetic Ni(III) complex 3 promotes a very strong antiferromagnetic interaction, leading to a singlet ground state.     

Immobilization of oxomolybdenum species in a layered double hydroxide pillared by 2,2'-bipyridine-5,5'-dicarboxylate anions

A Zn,Al layered double hydroxide (LDH) with Zn/Al = 1.45 and containing nitrate anions was prepared by coprecipitation and characterized by powder X-ray diffraction, Zn K-edge extended X-ray absorption fine structure spectroscopy (EXAFS), thermogravimetric analysis, FTIR and FT Raman spectroscopy, and (27)Al MAS NMR spectroscopy. Three Zn...O and four Zn...M (M = Zn, Al) shells could be fitted to the low-temperature (40 K) EXAFS spectrum, in accordance with a model for an ordered cationic sheet. The nitrate anions were easily exchanged by 2,2'-bipyridine-5,5'-dicarboxylate anions, resulting in an increase in the basal spacing from 9 to 18 A. The basal spacing of the pillared derivative indicates that the anions are arranged with their longest dimension nearly perpendicular to the host layers. This material exhibits a high encapsulating ability, as evidenced by its interaction with a dichloromethane solution of the dioxomolybdenum(VI) complex MoO(2)Cl(2)(THF)(2). A material with a metal loading of 11.2 wt % was obtained. Molybdenum K-edge EXAFS analysis could not substantiate the formation of a supported complex of the type MoO(2)Cl(2)(N-N) but instead indicated the formation of unidentate-bridged entities of the type [O(2)Mo-O-MoO(2)] with a metal-metal separation of 3.29 A. The molybdenum-containing LDH was active as a catalyst for the liquid-phase epoxidation of cis-cyclooctene, 1-octene, and trans-2-octene using tert-butyl hydroperoxide as the oxygen source, yielding the corresponding epoxides as the only products. For reactions carried out with no additional solvent (other than n-decane) or in the presence of 1,2-dichloroethane, the solid catalyst could be recycled with no major loss of activity. Other tests confirmed that the systems functioned as true heterogeneous catalysts.     

Unprecedented eight-palladium(I) crown-cycle with metal-metal unsupported bonds

Tri(N-pyrrolyl)phosphine reacted with the sigma/pi complex [Pd(mu-Cl)(COD-MeO)]2 to give the octa-cycle [Pd(mu-Cl)[P(pyrl)3]]8 containing four Pd(I)-Pd(I) unbridged bonds.     

Copper(II)-catalysed aerobic oxidation of primary alcohols to aldehydes

[CuBr2(2,2'-bipyridine)] catalyses the selective and very mild aerobic oxidation of primary alcohols to aldehydes in acetonitrile:water (2:1) in the presence of 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) and a base as cocatalysts.