Search results for "medium"

High yield synthesis of trinuclear [M3S4X3(diphos)3]+ (M=Mo, W; X=Cl, Br and diphos=dmpe, dppe) molecular clusters from solid state materials. Synthe…

2001

The excision of polymeric {M 3 S 7 X 4 } x (M=Mo, W; X=Cl, Br) cluster phases with diphosphines (dmpe, dppe) in acetonitrile affords a one step general synthetic route for the preparation of trinuclear molecular clusters with formula [M 3 S 4 X 3 (diphos) 3 ] + (M=Mo, W; X=Cl, Br and diphos=dmpe, dppe) in high yields. Following this strategy, the cluster cations [Mo 3 S 4 Br 3 (dmpe) 3 ] + and [W 3 S 4 Br 3 (dppe) 3 ] + have been prepared for the first time. This last tungsten cluster has proved to be a useful synthon for the synthesis of the hydride derivative [W 3 S 4 H 3 (dppe) 3 ] + in moderate yields. The crystal structure of [W 3 S 4 H 3 (dppe) 3 ](BPh 4 ) consists of a equilateral tu…

Structural Characterization and Magnetic Properties of the First 2,2‘-Bipyrimidine-Containing Iron(III) Complexes

1998

Two new iron(III) complexes of the formulas [Fe(bpm)Cl3(H2O)]·H2O (1) and [Fe2(bpm)Cl6(H2O)2]·2H2O (2) (bpm = 2,2‘-bipyrimidine) have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. 1 and 2 crystallize in the monoclinic system, space group P21/n, with a = 8.593(2) A, b = 17.669(4) A, c = 8.928(2) A, β = 102.36(2)°, and Z = 4 for 1 and a = 6.422(3) A, b = 11.999(4) A, c = 12.297(6) A, β = 93.82(4)°, and Z = 2 for 2. The structure of complex 1 is made up of neutral [Fe(bpm)Cl3(H2O)] mononuclear units and water molecules of crystallization. The monuclear units are linked through hydrogen bonds involving the coordinated water molecule and one of the…

The crystal and molecular structures of hexaquocobalt(II) diisonicotinate N-oxide and its isostructural nickel(II) homologue

1981

Abstract In this experiment the crystal and molecular structures of hexaaquocobalt(II)diisonicotinate N-oxide were determined from three-dimensional X-ray diffraction dat. The crystals belong to the monoclinic space group P2 1 /c. The cell parameters are a = 7.74(2), b = 9.826(2), c = 11.474(2) A , β = 91.08(2)°, V = 873.2(3) A 3 for the Co-complex, and a = 7.765(2), b = 9.725(6), c = 11.363 A , β = 91.20(3)°, V = 857.9(7) A 3 for the Ni-complex. Both structures were refined to a final R-value of 0.045. The X-ray structure analysis showed that there are metal(II)hexaquo cations and isonicotinate N-oxide anions formulated as Co(H 2 O) 6 2+ 2L − and Ni(H 2− O) 6 2+ 2L − in the structures. The…

Inside Cover: Regioselective Metal‐ and Reagent‐Free Arylation of Benzothiophenes by Dehydrogenative Electrosynthesis (Angew. Chem. Int. Ed. 40/2018)

2018

Molecule-Based Magnets Formed by Bimetallic Three-Dimensional Oxalate Networks and Chiral Tris(bipyridyl) Complex Cations. The Series [ZII(bpy)3][ClO…

2000

The synthesis, structure, and physical properties of the series of molecular magnets formulated as [ZII(bpy)3][ClO4][MIICrIII(ox)3] (ZII = Ru, Fe, Co, and Ni; MII = Mn, Fe, Co, Ni, Cu, and Zn; ox = oxalate dianion) are presented. All the compounds are isostructural to the [Ru(bpy)3][ClO4][MnCr(ox)3] member whose structure (cubic space group P4(1)32 with a = 15.506(2) A, Z = 4) consists of a three-dimensional bimetallic network formed by alternating MII and CrIII ions connected by oxalate anions. The identical chirality (lambda in the solved crystal) of all the metallic centers determines the 3D chiral structure adopted by these compounds. The anionic 3D sublattice leaves some holes where th…

Intrinsic Metal Size Effect on Adsorption of Organic Molecules on Platinum

2008

Di-σ adsorbed ethene, bridge(30) adsorbed benzene (with four di-σ-type and two π-type interactions), and η1 and η2 adsorbed acetone on nanosized platinum clusters consisting of 19 to 38 Pt atoms were studied theoretically by density functional theory (DFT) calculations with general gradient approximation (GGA) utilizing plane wave and local basis sets. The cluster results were compared to plane wave calculations employed with periodic boundary conditions. It was found that the geometries obtained with different methods are very similar but the adsorption energy depends prominently on the cluster size. Adsorption was strongest on the 22- and 26-atom clusters and weakest on the 35- and 38-ato…

Synthesis, Characterization, and Properties of Some Copper( II ) Complexes of 2‐Pyridineformamide Thiosemicarbazone (HAm4DH)

2006

Reactions between different copper(II) salts and 2-pyridineformamide thiosemicarbazone (HAm4DH) in neutral ethanolic media led to the formation of complexes with the formulae [Cu(HAm4DH)X2] (X = Cl or Br) (1, 2) and [Cu(HAm4DH)2]X2 (X = NO3 or ClO4) (3, 4). The same reactions carried out in the presence of triethylamine gave rise to new complexes with the general formulae [Cu(Am4DH)X] (X = Cl, Br, AcO, or NO3) (5–8), [Cu(H2O)(Am4DH)](ClO4) (9), and [Cu(Am4DH)2] (10), many of which were isolated with different molecules of crystallization and contain a deprotonated thiosemicarbazone (Am4DH). These complexes were characterized by elemental analysis, and different spectroscopic and magnetic te…

Mössbauer spectroscopic studies on compounds containing tin-cadmium and tin-zinc bonds

1975

The Mossbauer parameters of compounds Ph3Sn MCl · TMED (M = Cd, Zn; TMED = N,N,N′,N′-tetramethylethylenediamine), (Ph3Sn)2CdL2 (L2 = TMED, 2,2′-bipyridine and o-phenanthroline) and (Ph3Sn)2 Zn · TMED have been determined and are discussed in connection with Mossbauer data concerning Ph3SnIV derivatives with other Sn-metal bonds. The isomer shift values suggest a high s character in SnCd and SnZn bonds resulting in deviations from regular tetrahedral environments around tin. Experimental quadrupole splittings and calculated partial quadrupole splitting values indicate reduced donor abilities towards the tin atom of an individual Ph3SnIV moiety by Cd-and Zn(Ph3Sn)1−nClnL2 (i.e., the remaini…

Some observations on the fluorometric determination of metallic elements in micellar media

1989

Abstract Experimental evidence is given allowing us to interpret why the detection limits obtained in micellar media are higher than those expected according to fluorescence enhancements for the niobium-lumogallion-tartrate system in the presence of different nonionic surfactants. The residual fluorescence of the surfactant solution and the competitive interaction with micelles between complexes and free ligands were studied. Near the critical micelle concentration of surfactants, remarkable changes in the emission spectra were observed in the case of both complex and free ligand solutions, which indicate the existence of interactions between the chemical system and surfactant monomers and …

Understanding Digestive Ripening of Ligand-Stabilized, Charged Metal Nanoparticles

2017

Most syntheses of thiolate-protected metal nanoparticles (NPs) include a thermochemical step in which the as-prepared, polydisperse NPs are transformed to a narrower size distribution in a poorly understood process known as digestive ripening (DR). Previous theoretical approaches considered either surface and electrostatic contributions or surface and ligand-binding contributions. We show that the three contributions are needed to obtain theoretical predictions in agreement with experimental observations. Although statistical thermodynamics does not clarify mechanistic details, it certainly provides valuable insights on the DR process. Remarkably, a relatively simple theory with no fitting …