Further observations on the cobalt(II)-chloride equilibrium: Effect of changing the chloride ion concentration

Abstract

As previously noted1-2, the ligand substitution reaction [Co(h2o)

Spectroscopic and solid-state evaluations of tetra-aza macrocyclic cobalt complexes with parallels to the classic cobalt(II) chloride equilibrium

“…When new heterocycles are synthesized, the complexes formed with Co(II)/Co(III) ions can be compared to these more classic coordination compounds in order to delineate the observed reactivity [17]. One specific example of a classic Co(II) coordination complex is the equilibrium between pink cobalt(II) hexahydrate and blue cobalt(II) tetrachloride (scheme 1); this well-characterized demonstration is often used to illustrate Le Chatelier's Principle [20][21][22][23][24][25][26]. Scheme 1.…”

“…Scheme 1. Equilibrium reaction between cobalt(II) hexahydrate and cobalt(II) tetrachloride used to demonstrate Le Chatelier's Principle [20][21][22][23][24][25][26].…”

“…The color change in organic vs. aqueous solvents, as well as the presence of a cobalt, led us to examine the classic cobalt(II) chloride equilibrium to determine if there were any parallels to our ligand system [20][21][22][23][24][25][26].…”

Microwave Mapping Demonstration Using the Thermochromic Cobalt Chloride Equilibrium

“…This equilibrium responds to chloride concentration, solvent composition, and heat. The relative position of the equilibrium responds to these various stresses and is nicely illuminated by the various colors of the cobalt complexes. heat + [ Co ( H 2 O ) 6 ] 2 + ( aq ) false( pink false) + 4 Cl ( aq ) − ⇌ false[ CoCl 4 false] 2 − ( aq ) false( blue false) + 6 normalH 2 normalO false( normall false) Variations of this demonstration have been discussed in several articles − in this Journal . Bare and Mellon reported painting the aqueous cobalt chloride solution on filter paper and developing the filter paper with a heat gun by driving off the water, thus shifting the equilibrium to the blue [CoCl 4 ] 2– complex (eq ).…”

Spectrophotometric Titration of Cobalt(II) with CaCl2 in Mixed Solvents of 2-Propanol and Water for the Analysis of the Extraction Mechanism of Cobalt(II) by Salting-out in the Presence of CaCl2

“…The color change of an aqueous Co(II) solution from pink to blue upon the addition of Cl -is a wellknown phenomenon and is ascribed to the conversion of Co(H2O)6 2+ to CoCl4 2-. [10][11][12][13] However, no work has been done on the formation of CoCl4 2-in mixed aqueous solvents, especially in a mixture of 2-propanol and water.…”