Mixed-ligand complexes in mercury(II)-cyanide-iodide solutions: a Raman and ultraviolet study

Abstract

Raman spectra of Hg(I1) in aqueous NaCN-Sa1 show peaks unique to the mixtures a t 2157,2180-2200, and 318-330 cm-l. The first of these is assigned t o Hg(CN)JZ-on the basis of observed trends with solution composition. The last two show variations in position with NaI concentration and have been assigned to the general composition Hg(CN)21,Z-. Raman spectra of Hg(CN)JZZ-solutions show remarkable similarity to the spectrum of solid K I . Hg(CN)% in which essentially linear Hg(CN)Z groups are coordinated by equatorial iodides Study of the disappearance of the 3225-A peak of H g L -, when 5 X NaI solutions dilute in Hg(1I) are made several millimolar in NaCN, indicates formation of Hg(CN)112-and H g ( C N ) & -. One additional mixed-ligand complex, namely, Hg(CX)I, is fo:med from Hg(CN)% and HgI2 with a formation constant of 0.14. This n e x complex exhibits a n ultraviolet peak a t 2370 A. IntroductionMercuric ion is a class B ion and forms strong complexes with both cyanide and iodide. The stepwise formation constants for the mono and di ligand complexes are about five orders of magnitude greater for cyanide than for iodide; the stepwise constants for the tri-and tetraligand complexes, in contrast, are of the same order of magnitude.? This paper reports a study of a number of the mixed-ligand complexes using Raman and ultraviolet spectrometry.

Stability and Kinetics of Acid- and Anion-Assisted Dissociation Reactions of Hexaamine Macrobicyclic Mercury(II) Complexes

“…Concentrations of HgI 4 2were determined from the absorbance maximum at 322 nm using the value ) 1.97 × 10 4 M -1 cm -1 (I ) 5 M NaI). 24 The stability constants were calculated using the programs SUPERQUAD 25 and KaleidaGraph, 26 and the formation constants for HgI3 -and HgI4 2were taken to be β 3 ) 10 27.6 M -3 and β4 ) 10 29.8 M -4 (I ) 0.5 M, 25 °C), respectively. 27,28 The approach to equilibrium from the direction HgI4 2-+ L was hampered by the formation of an amorphous precipitate in the concentration range 0.06 M < [I -] < 0.2 M. However, when solutions of HgI 2, NaI, NaOH, and NaClO4 were mixed with solutions of sar, no precipitation was observed for [I -] g 0.2 M and [I -] e 0.06 M. At these concentrations good agreement between the sets of experiments was observed.…”

“…Sodium iodide concentrations ranged from 0.02 to 0.40 M ensuring that the amount of HgI 4 2- varied from 10% to 90% of total mercury(II). Concentrations of HgI 4 2- were determined from the absorbance maximum at 322 nm using the value ε = 1.97 × 10 4 M -1 cm -1 ( I = 5 M NaI) and KaleidaGraph, and the formation constants for HgI 3 - and HgI 4 2- were taken to be β 3 = 10 27.6 M -3 and β 4 = 10 29.8 M -4 ( I = 0.5 M, 25 °C), respectively. , …”

Über Cyanohalogenomercurate der Alkalimetalle / On Cyanohalogenomercurates of Alkali Metals

“…Die von Harth [21] beschriebenen gemischten Tetracyanohalogenomercurate M2Hg(CN, X)4 konnten zumindest in kristalliner Form nicht erhalten werden. Hinweise auf das Auftreten solcher Komplexe in Lösungen werden von mehreren Autoren [17,19,[22][23][24] RbHg(CN)2Br [12] CsHg ( CN-Gruppen beteiligt. Das I-Ion bildet nur sehr schwache, elektrostatische Wechselwirkungen mit den Kationen aus.…”