A Novel Electrophilic Diamination Reaction of Alkenes.

A three-component electrophilic reaction transforms olefins into imidazoline and diamine derivatives. Rhodium(II) heptafluorobutyrate dimer (2 mol %) was utilized as the catalyst and N,N-dichloro-p-toluenesulfonamide (TsNCl ) and acetonitrile as the nitrogen sources. Modest to good yields (45-82 %) and high regio- and stereoselectivity were achieved.

Dendron-Controlled Nucleation and Growth of Gold Nanoparticles.

Passivation of the metal surface by dendrons bearing a focal 4-pyridone functionality (the second-generation dendron is shown; C: gray, N: blue, O: red) allows controlled nucleation and growth of gold nanoclusters. The particle size is a direct function of the generation number of the dendritic ligands, with higher generation dendron producing larger particles.

Synthesis and bioactivity studies of two isosteric acyclic analogues of melanin concentrating hormone.

Salmon melanin concentrating hormone (MCH) is a cyclic heptadecapeptide. MCH stimulates perinuclear aggregation of melanosomes within integumental melanocytes of teleost fishes resulting in skin blanching. MCH contains a disulfide bridge forming a 10-residue ring [sequence: see text].

Formation constants of Cd(II) complexes with dithizone and related compounds.

The stability constants of cadmium complexes of compounds related to dithizone are reported. Substitution in the ortho position lowers the stability constant. It is probable that this is a consequence of deviation from coplanarity of the phenyl and chelate rings.

Sulphonated azo-dyes as extractive metallochromic reagents.

A survey has been made of analytically useful extractable ion-pair complexes that are formed by the use of a series of metallochromic indicator-metal complexes in conjunction with quaternary ammonium ions. The reagents were o,o'-dihydroxyazo dyes and azo-oxines.

Stability constants of some metal dithizonates.

The overall stability constants of electroneutral dithizonates of bismuth, cadmium, cobalt(II), copper(II), iron(II), lead(II), manganese(II), mercury(II), nickel, palladium(II), silver, tin(II) and zinc were determined by means of stoichiometric dilution in aqueous solution stabilized by hydroxylamine hydrochloride, at pH 5.50-10.02.

Crystal and molecular structure of zinc dithizonate.

The structure of zinc(II) dithizonate has been determined by X-ray analysis. The co-ordination round the zinc is slightly distorted tetrahedral and the proximal phenyl rings have been shown to be almost coplanar with the chelate rings.

Analytical applications of mixed ligand extraction equilibria Nickel-ditbizone-phenanthroline complex.

The mixed ligand nickel-dithizone-phenanthroline complex provides a sensitive method for determination of nickel and also permits evaluation of the extraction constant for nickel dithizonate. The value log K(ex) = -0.7 was obtained, in agreement with a value of -0.

Acid dissociation and metal chelate formation equilibria of some halogenated diphenylthiocarbazones.

The acid dissociation constants (K(a)) of di-p-fluoro-, di-p-chloro-, di-p-bromo-, di-p-iodo-and di-m-trifluoromethylphenylthiocarbazones and the equilibrium formation constants (K(f(1))) of their 1:1 complexes with Co(II), Ni and Zn have been determined at 25 degrees in 50% v v aqueous dioxan at 0.10 M ionic strength. Each of the electron-withdrawing substituents gives a reduction in pK(a) roughly proportional to its Hammett sigma value, and log K(f(1)) increases linearly with pK(a).

Determination of 2,3-dimercaptopropanol-l (BAL) by titration with zinc, with eriochrome black T as indicator.

A method is proposed for the titrimetric determination of BAL with zinc solution and Eriochrome Black T (EBT) as indicator. It is based on the difference of the stabilities of the Zn(BAL)a and Zn-EBT complexes. The accuracy of the method is very good and the interference of diverse mercaptans is limited to those compounds forming zinc complexes more stable than the Zn-EBT complex.

A highly sensitive extraction-photometric method for nickel with dithizone and phenanthroline.

Addition of phenanthroline to nickel dithizonate in chloroform results in a mixed ligand complex, NiDz(2)phen, the high molar absorptivity of which (49.1 x 10(3)) results in a colorimetric estimation of nickel that is significantly more sensitive than any other method.

Some solvent effects on the solvent extraction of 8-quinolinol.

The distribution constants of 8-quinolinol between water and a series of substituted aliphatic hydrocarbons, at 25 degrees , are reported. The results are discussed in terms of dielectric constant and solubility parameter of the solvents. For 8-quinolinol, and possibly for its chelates, bromochloromethane, dibromomethane and chloroform seem to be about the best solvents, in that order.