Polarography of some coordination compounds of Platinum. III. Ions of the tetrammineplatinum(II) type

A number of tetrammine ions of divalent platinum, in which the ligands were ammonia, methylamine, dimethylamine, ethylenediamine, pyridine, aniline, and combinations of some of these, were studied at the dropping mercury electrode. Some of the ions showed maxima in their current-voltage curves (c-v curves). The formation of hydrogen interfered with the c-v curves of other ions, so that limiting currents were not obtainable. A method was devised for the measurement of a voltage by means of which the ease of reduction of the ions could be compared. Using a supporting electrolyte of 0.1M KCl and 0.01% gelatin, the order of increasing ease of reduction was found to be When the ammonia groups of [Pt(NH3)4]2+ were successively replaced by pyridine groups, the resulting e-v curves shifted progressively to more positive voltages. It was also found that cis- and trans-isomers of [PtA2B2]2+ reduced at different voltages. The trans-isomer reduced more readily

Polarography of some coordination compounds of platinum. I. Hexammineplatinum (IV) and Tris(ethylenediamine)platinum(IV) ions

The polarographic reduction of tris(ethylenediamine)platinum(IV) and the hexammineplatinum(IV) ions has been studied in potassium chloride, potassium nitrate, and potassium nitrate plus ammonia solutions. Both ions were reduced irreversibly producing similarly shaped waves, showing well-defined diffusion current regions corresponding to two-electron reductions of the complexes. A linear relationship existed between diffusion current and concentration within the range examined. In aqueous potassium chloride and potassium nitrate media, the waves contained slight inflexions at positions corresponding to one-electron additions. The phenomenon suggested the transient presence of platinum(III) ions, and indicated that the half-wave potential of the reduction of the complexes to the trivalent state was very close to the half-wave potential of the reduction from platinum(IV) to platinum(II). The values were so close together as to indicate the improbability of isolating the trivalent complexes. Gelatin enhanced the inflexion in the wave but shifted the wave in a more negative direction. An increased concentration of supporting electrolyte also shifted the wave to a more negative position. In all cases a continuous discharge began at about —1·3 V (v. S.C.E.). This discharge was so far removed from that of the potassium ions of the supporting electrolyte that it was attributed to the discharge of hydrogen. Since the initial reduction of the platinum complexes corresponded to a two-electron change, it can be represented by reduction to a tetrammine ion. It is postulated that at higher applied potentials (namely, —1·3 V v. S.C.E.) the reduction proceeded further, producing platinum metal. This platinum metal would be in an active state, insoluble in mercury, and being on the surface, would lower the overvoltage of hydrogen leading to its discharge at a more positive potential than on a pure mercury surface. This view was supported by the fact that gas bubbles were observed at the dropping electrode when a voltage greater than —1·3 V was applied to the electrode for some time. When ammonia was added to the supporting electrolyte, a wave, without an inflexion, and corresponding to an irreversible two-electron reduction, was obtained at more negative potentials. The bivalent tetrammineplatinum(II) and bis(ethylenediamine)platinum(II) ions also gave polarograms showing the continuous discharge of hydrogen

Polarography of some coordination compounds of platinum. IV. compounds of platinum(II) containing 1,10–Phenanthroline

Four ions were studied at the dropping mercury electrode. They were [Pt(ophen)2]2-, [Pt(ophen)(en)]2-, [Pt(ophen)(py)2]2-, and [Pt(ophen)(py)Cl]−, where ophen= 1,10–phenanthroline, en=ethylenediamine, and py=pyridine. The shapes of the c-v curves of the ions in supporting electrolyte 0.1M KCl, were dependent on complex ion concentration. Adsorption phenomena occurred with some ions but the effects decreased as the complex ion concentration decreased. The reduction of [Pt(ophen)2]2- produced evidence for compounds of platinum with valency less than two. Reduction of the other ions appeared to proceed directly to metallic platinum

Platinum(II) complexes of 2,2',2'',2'''-tetrapyridine

Platinum(II) complexes of the general formula PtLX, yHO where L = 2,2',2'',2'''-tetrapyridine (tpy), X = I, ClO, BPh, y = 0; X = NO, y = 3, have been isolated. Conductometric and infrared evidence suggest that the ligand can function as a quadridentate

Visible absorption characteristics of the bis-(2,9-dimethyl-1,10-phenanthroline)- and bis-(4,4′,6,6′-tetramethyl-2,2′-bipyridine)-copper(I) ions

Spectrophotometric studies have indicated that the absorbing species in solution for the determination of copper using 2,9-dimethyl-1,1 0-phenanthroline (dmp) and 4,4’,6,6’-tetramethyl-2,2’-bipyridine (tmb) are the bis complex ions, [Cu(dmp)] and [Cu(tmb)], respectively. Solutions of the pure compounds, [Cu(ligand)] X where X = Cl, Br, I, NO, and ClO, have spectral characteristics in agreement with the earlier studies. In general, however, the solutions conform to Beer's law only when a large excess of the ligand is added. Deviations from Beer's law in the absence of excess ligand are attributed to dissociation of the [Cu-(ligand)]X complexes to the corresponding monochelate species. These ligands coordinate to many transition metals and their apparent specificity for copper in extraction procedures is probably due to complexes of other metals having wavelengths of maximum absorption well removed from the λ values for the copper complexes, or much lower molar absorptivities

Structural studies on mono-2,9-dimethyl-1,10-phenanthroline complexes of some divalent metal chlorides

The X-ray powder spectra of MIICl2 dmp, where MII Mn, Fe, Co, α - Ni (yellow), β - Ni (purple), Cu, Zn and dmp = 2,9-dimethyl-1,10-phenanthroline, show that the complexes of Fe, Co and β - Ni are isomorphous with ZnCl2 dmp. In this complex, the zinc atom is tetrahedrally co-ordinated. The Mn, α - Ni and Cu complexes are all structurally different

Coordination compounds of substituted 1, 10-phenanthrolines and related dipyridyls iii. Complexes of copper and 2, 9-dimethyl-1, 10-phenanthroline

Solutions of copper(II) salts and excess 2, 9-dimethyl-1, 10-phenanthroline (dmp) in organic solvents yielded complexes of formula Cu(dmp), X,.H, O, where X=NO3, Cl, and Br. When excess of the copper(II) salt was present, mono complexes represented by CudmpX2, where X=NO3, Cl, Br; 2X=SO4 were obtained. Copper(II) perchlorate-dmp mixtures yielded hydrated Cu(dmp),(ClO4)2. Aqueous solutions of the bis complexes changed colour when boiled and deposited red crystals of composition Cu(dmp)2X, with water of crystallization in some cases. Bis(dmp)copper(I) nitrate, perchlorate, and sulphate were also produced by reduction of the copper(II) complexes with hypophosphorus acid or hydroxylamine salts. The visible absorption curves for solutions of the complexes Cu(dmp)2X, corresponded with those reported in studies of the spectrophotometric estimation of copper using dmp. Mono complexes of formula CudmpX, where X=Cl, Br, and I, were prepared by reduction of the corresponding copper(II) complexes

Metal complexes of some hybrid bidentate ligands containing tertiary arsine and primary amine donor groups. II. Compounds of nickel and copper

Some first transition series metal complexes of the three new tertiary arsine-primary amine bidentate ligands, o-dimethylarsinoaniline (MAA), o-diphenylarsinoaniline (PAA), and 1-amino-2-(diphenylarsino)ethane (APE), have been prepared, and their structures elucidated by physico-chemical studies. Octahedral high spin complexes of the type Ni(ligand)2X2 (where X = halogen, NCS or NO3) were obtained for all three ligands. Only in the case of the weakly coordinating perchlorate ion were low spin four-coordinate compounds of formula [Ni(ligand)2](ClO4)2 isolated. The products from the reactions of the ligands with copper(II) salts were (i) complexes of copper(II); (ii) complexes of copper(I); (iii) complexes of the corresponding arsine oxide with copper(II). In the case of MAA, examples of each of the three types of product were obtained. The complexes, [Cu(ligand)2](ClO4)2 (where ligand = MAA or PAA), which are stable as solids, apear to be the first known examples of complexes of tertiary arsines with copper(II)