Linkage Isomerism in Cobalt(Iii) Complexes
Linkage isomerism in cobalt(III) complexes
Author: M Hurley
Abstract
Preparation of nitrito-kO-complex was prepared by ligand substitution from a chloridio-complex chemically made. The nitro-kN-complex was then prepared by isomerisation of the nitrito-kO-complex. Visible absorption and infrared spectroscopy was then carried out on all three complexes. The molar absorption coefficients calculated were 38.0 cm-1 mol-1 L for the chloridio-complex, 76.0 cm-1 mol-1 L for the nitrito-kO-complex and 85.4 cm-1 mol-1 L for the nitro-kN-complex these values are directly related to the absorption values which correspond to the colour of the complexes.
Introduction
“A ligand is an ion or molecule that binds to a central metal atom to form a co-ordination complex”( Miessler, Gary L, 1999). This usually involves donation of one or more of the ligands electron pairs. Ligands that can bind via two or more atoms to form linkage isomers like thiocyanate (NCS-). Some ligands are better than others by having faster rates of equilibrium and exchange ligands very quickly. Examples of linkage isomerism are cobalt (III) complexes pentaamminenitro-kN-cobalt (III) and pentaamminenitro-kO-cobalt (III) which will be chemically prepared and investigated. The preparation of pentaamminenitro-kO-cobalt (III) will be performed by ligand substitution from a chemically prepared chlordio-complex while pentaamminenitro-kN-cobalt (III) will be prepared by isomerisation of the pentaamminenitro-kO-cobalt (III). “These complexes will be studied using their visible and infrared spectrum to understand linkage isomerism”(Lab manual, 2009).
Experimental
The use of the lab manual was used and followed with no alterations to the instructions.
A: Preparation of complexes
Pentaaminechloridocobalt(III) chloride, [CoCl(NH3)5]Cl5 (complex i)
Ammonia chloride (3.75g) was dissolved in concentrated ammonia solution (25ml) in a 125ml conical flask. Then the solution was continuously stirred
Author: M Hurley
Abstract
Preparation of nitrito-kO-complex was prepared by ligand substitution from a chloridio-complex chemically made. The nitro-kN-complex was then prepared by isomerisation of the nitrito-kO-complex. Visible absorption and infrared spectroscopy was then carried out on all three complexes. The molar absorption coefficients calculated were 38.0 cm-1 mol-1 L for the chloridio-complex, 76.0 cm-1 mol-1 L for the nitrito-kO-complex and 85.4 cm-1 mol-1 L for the nitro-kN-complex these values are directly related to the absorption values which correspond to the colour of the complexes.
Introduction
“A ligand is an ion or molecule that binds to a central metal atom to form a co-ordination complex”( Miessler, Gary L, 1999). This usually involves donation of one or more of the ligands electron pairs. Ligands that can bind via two or more atoms to form linkage isomers like thiocyanate (NCS-). Some ligands are better than others by having faster rates of equilibrium and exchange ligands very quickly. Examples of linkage isomerism are cobalt (III) complexes pentaamminenitro-kN-cobalt (III) and pentaamminenitro-kO-cobalt (III) which will be chemically prepared and investigated. The preparation of pentaamminenitro-kO-cobalt (III) will be performed by ligand substitution from a chemically prepared chlordio-complex while pentaamminenitro-kN-cobalt (III) will be prepared by isomerisation of the pentaamminenitro-kO-cobalt (III). “These complexes will be studied using their visible and infrared spectrum to understand linkage isomerism”(Lab manual, 2009).
Experimental
The use of the lab manual was used and followed with no alterations to the instructions.
A: Preparation of complexes
Pentaaminechloridocobalt(III) chloride, [CoCl(NH3)5]Cl5 (complex i)
Ammonia chloride (3.75g) was dissolved in concentrated ammonia solution (25ml) in a 125ml conical flask. Then the solution was continuously stirred
References: Miessler, Gary L; Donald Arthur Tarr ,(1999), Inorganic chemistry, Pg 642 Department of chemistry lab manual, CHEM281-09S2-LAB