Coordination Complexes of Cobalt: Advanced Inorganic Chemistry Lab
Coordination Complexes of Cobalt
Advanced Inorganic Chemistry Lab
02/27/2015
Abstract When the transition metal, cobalt, forms a complex involving a nitrate ion, the ligand has the ability to coordinate via N or O. The ability of the nitrate to attach via the N or O gives rise to the term, linkage isomers and can affect the functionality of the complex with other molecules. To explore structural differences between complexes, pentaaminechlorocobalt (III) chloride, pentaaminenitritocobalt (III) chloride, and pentaaminenitrocobalt (III) chloride were synthesized and isolated. From the ultraviolet-visible spectrum, infrared spectrum, and molar conductivity each compounds was distinguished and characterized to show fundamental differences between the three. Furthermore, IR spectroscopy is suitable for distinguishing between the nitro- and nitrito-linkage isomers because they have different vibrational patterns from one another. Given enough time, the more stable thermodynamic linkage isomer [Co(NH3)5NO2]Cl2 will be formed as the major product over the kinetic product, [Co(NH3)5ONO]Cl2.
Introduction
The ultraviolet-visible (UV/Vis) spectrum of cobalt complexes has been analyzed to determine the fundamental differences in the structures of each molecule.1 Ligands can coordinate to a central ion in more than one way, which can change its interactions with molecules. The cobalt complex being investigated in this experiment has a pair of linkage isomers, with a ligand having the ability to coordinate via N or O. The preparation of cobalt (III) pentamine complexes is done through oxidation using hydrogen peroxide to convert the metal from the +2 to the +3 oxidation state.1
Furthermore, displacement reactions are then performed to synthesize the linkage isomers. Depending on which isomer is present, could affect the functionality of the molecule. The linkage isomers were both prepared and distinguished by infrared (IR) spectrum.2 Molar conductivity is used as a
Advanced Inorganic Chemistry Lab
02/27/2015
Abstract When the transition metal, cobalt, forms a complex involving a nitrate ion, the ligand has the ability to coordinate via N or O. The ability of the nitrate to attach via the N or O gives rise to the term, linkage isomers and can affect the functionality of the complex with other molecules. To explore structural differences between complexes, pentaaminechlorocobalt (III) chloride, pentaaminenitritocobalt (III) chloride, and pentaaminenitrocobalt (III) chloride were synthesized and isolated. From the ultraviolet-visible spectrum, infrared spectrum, and molar conductivity each compounds was distinguished and characterized to show fundamental differences between the three. Furthermore, IR spectroscopy is suitable for distinguishing between the nitro- and nitrito-linkage isomers because they have different vibrational patterns from one another. Given enough time, the more stable thermodynamic linkage isomer [Co(NH3)5NO2]Cl2 will be formed as the major product over the kinetic product, [Co(NH3)5ONO]Cl2.
Introduction
The ultraviolet-visible (UV/Vis) spectrum of cobalt complexes has been analyzed to determine the fundamental differences in the structures of each molecule.1 Ligands can coordinate to a central ion in more than one way, which can change its interactions with molecules. The cobalt complex being investigated in this experiment has a pair of linkage isomers, with a ligand having the ability to coordinate via N or O. The preparation of cobalt (III) pentamine complexes is done through oxidation using hydrogen peroxide to convert the metal from the +2 to the +3 oxidation state.1
Furthermore, displacement reactions are then performed to synthesize the linkage isomers. Depending on which isomer is present, could affect the functionality of the molecule. The linkage isomers were both prepared and distinguished by infrared (IR) spectrum.2 Molar conductivity is used as a
References: 1. Williams, G.M.; Olmsted III, J.; Breksa III, A.P. Coordination Complexes of Cobalt. J. Chem. Educ., 1989, 66 (12), 1043-1045. 2. Penland, R.B.; Lane, T.J.; Quagliano, J.V. Infrared Absorption Spectra of Inorganic Coordination Complexes. VII. Structural Isomerism of Nitro- and Nitritopentaaminechloride (III) Chloride. J. Am. Chem. Soc., 1956, 78 (5), 887-889.