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 [Pt{(CH3)2NH)4]2+
= [Pt(NH3)4]2+ = [Pt(NH3)3(C5H5N)]2+
= [Pt{C2H4(NH2)2}2]2+
< cis-[Pt(NH3)2(C5H5N)2]2+
< trans-[Pt(NH3)2C5H5N)2]2+
< [Pt(CH3NH2)4]2+ = [Pt(NH3)(C5H5N)3]2+
<[Pt(C6H5N)4]2+ < cis-[Pt(NH3)2(C6H5NH2)2]2+
< trans-[Pt(NH3)2(C6H5NH2)2]2+.
When the ammonia groups of
[Pt(NHS),l2+ 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 [PtA,B,I2+ reduced at different voltages. The
trans-isomer reduced more readily.
Studies on the Vibrated Dropping Mercury Electrode. II. Electrocapillary Characteristics of the Current-Voltage Curve
