Octahedral-tetrahedral coordination equilibria of nickel (II) and copper (II) in concentrated aqueous electrolyte solutions

Charles Angell, D. M. Gruen

Research output: Contribution to journalArticle

57 Citations (Scopus)

Abstract

The coordination states of Ni(II) and Cu(II) in aqueous magnesium chloride solutions have been studied spectrophotometrically at temperatures up to 320° and concentrations up to 8 M in magnesium chloride. For Ni(II), increase in the MgCl2 concentration results in the replacement of H2O in the first coordination sphere of Ni(H2O)6 2+ by Cl- to give NiCl6 4- groups. With increasing temperature, transformation to NiCl4 2- groups occurs through a two-species octahedral-tetrahedral equilibrium. Thermodynamic data are presented for this equilibrium. For Cu(II), at similar temperatures and MgCl2 concentrations, the coordination state is the CuCl4 2- configuration, but in this case the transition from Cu(H2O)6 2+ cannot be described in terms of a two-species equilibrium but seems to occur by means of a continuous ligand exchange and distortion mechanism. In the MgCl2-H2O system, H2O coordinates strongly with Mg(II). For compositions near H2O/Mg = 6, the Mg(H2O)6 2+ species appears to exist as an independent entity. It is pointed out that changes in the Ni(II) coordination states can serve as indicators for the determination of Mg(II) hydration numbers as well as hydration numbers of other noble gas configuration cations in molten hydrate systems.

Original languageEnglish (US)
Pages (from-to)5192-5198
Number of pages7
JournalJournal of the American Chemical Society
Volume88
Issue number22
StatePublished - 1966
Externally publishedYes

Fingerprint

Magnesium Chloride
Nickel
Electrolytes
Copper
Hydration
Magnesium
Temperature
Inert gases
Hydrates
Molten materials
Noble Gases
Positive ions
Ligands
Thermodynamics
Cations
Chemical analysis

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{978c663cd5ba49e0b90a3282b44ff022,
title = "Octahedral-tetrahedral coordination equilibria of nickel (II) and copper (II) in concentrated aqueous electrolyte solutions",
abstract = "The coordination states of Ni(II) and Cu(II) in aqueous magnesium chloride solutions have been studied spectrophotometrically at temperatures up to 320° and concentrations up to 8 M in magnesium chloride. For Ni(II), increase in the MgCl2 concentration results in the replacement of H2O in the first coordination sphere of Ni(H2O)6 2+ by Cl- to give NiCl6 4- groups. With increasing temperature, transformation to NiCl4 2- groups occurs through a two-species octahedral-tetrahedral equilibrium. Thermodynamic data are presented for this equilibrium. For Cu(II), at similar temperatures and MgCl2 concentrations, the coordination state is the CuCl4 2- configuration, but in this case the transition from Cu(H2O)6 2+ cannot be described in terms of a two-species equilibrium but seems to occur by means of a continuous ligand exchange and distortion mechanism. In the MgCl2-H2O system, H2O coordinates strongly with Mg(II). For compositions near H2O/Mg = 6, the Mg(H2O)6 2+ species appears to exist as an independent entity. It is pointed out that changes in the Ni(II) coordination states can serve as indicators for the determination of Mg(II) hydration numbers as well as hydration numbers of other noble gas configuration cations in molten hydrate systems.",
author = "Charles Angell and Gruen, {D. M.}",
year = "1966",
language = "English (US)",
volume = "88",
pages = "5192--5198",
journal = "Journal of the American Chemical Society",
issn = "0002-7863",
publisher = "American Chemical Society",
number = "22",

}

TY - JOUR

T1 - Octahedral-tetrahedral coordination equilibria of nickel (II) and copper (II) in concentrated aqueous electrolyte solutions

AU - Angell, Charles

AU - Gruen, D. M.

PY - 1966

Y1 - 1966

N2 - The coordination states of Ni(II) and Cu(II) in aqueous magnesium chloride solutions have been studied spectrophotometrically at temperatures up to 320° and concentrations up to 8 M in magnesium chloride. For Ni(II), increase in the MgCl2 concentration results in the replacement of H2O in the first coordination sphere of Ni(H2O)6 2+ by Cl- to give NiCl6 4- groups. With increasing temperature, transformation to NiCl4 2- groups occurs through a two-species octahedral-tetrahedral equilibrium. Thermodynamic data are presented for this equilibrium. For Cu(II), at similar temperatures and MgCl2 concentrations, the coordination state is the CuCl4 2- configuration, but in this case the transition from Cu(H2O)6 2+ cannot be described in terms of a two-species equilibrium but seems to occur by means of a continuous ligand exchange and distortion mechanism. In the MgCl2-H2O system, H2O coordinates strongly with Mg(II). For compositions near H2O/Mg = 6, the Mg(H2O)6 2+ species appears to exist as an independent entity. It is pointed out that changes in the Ni(II) coordination states can serve as indicators for the determination of Mg(II) hydration numbers as well as hydration numbers of other noble gas configuration cations in molten hydrate systems.

AB - The coordination states of Ni(II) and Cu(II) in aqueous magnesium chloride solutions have been studied spectrophotometrically at temperatures up to 320° and concentrations up to 8 M in magnesium chloride. For Ni(II), increase in the MgCl2 concentration results in the replacement of H2O in the first coordination sphere of Ni(H2O)6 2+ by Cl- to give NiCl6 4- groups. With increasing temperature, transformation to NiCl4 2- groups occurs through a two-species octahedral-tetrahedral equilibrium. Thermodynamic data are presented for this equilibrium. For Cu(II), at similar temperatures and MgCl2 concentrations, the coordination state is the CuCl4 2- configuration, but in this case the transition from Cu(H2O)6 2+ cannot be described in terms of a two-species equilibrium but seems to occur by means of a continuous ligand exchange and distortion mechanism. In the MgCl2-H2O system, H2O coordinates strongly with Mg(II). For compositions near H2O/Mg = 6, the Mg(H2O)6 2+ species appears to exist as an independent entity. It is pointed out that changes in the Ni(II) coordination states can serve as indicators for the determination of Mg(II) hydration numbers as well as hydration numbers of other noble gas configuration cations in molten hydrate systems.

UR - http://www.scopus.com/inward/record.url?scp=33947337595&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33947337595&partnerID=8YFLogxK

M3 - Article

VL - 88

SP - 5192

EP - 5198

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 22

ER -