Synthesis and Characterization of
Hexaaminecobalt(III) Chloride and
Pentaamminefluorocobalt(III) Nitrate Monohydrate
Lab Report
Rui Ning
AB8
April 2th, 2014
Abstract This experiment explored the synthesis of one known compound Q (Hexaaminecobalt(III) Chloride) and one unknown compound S. The purpose of this lab is to characterize the unknown compound and study the basic synthesize process of cobalt complexes. In order to identify the unknown compound, four characterization tests were performed using both compounds to determine the molar mass, non-ammonia ligands, the charge of the complex ion and the number of ammonia legends. As a result, the molar mass test related the absorbances of both compounds with the grams used and molecular weight to give a molar mass of 307.11 g/mole for the unknown compound. The non-ammonia ligands test using UV-vis showed that the maximum wavelength for the ligand of compound S was 518 nm. Therefore, the ligand was determine to be Co(NH3)5F2+. A charge test using ion exchange column and titration also corresponded with this result and showed that the ligand has a 2+ charge after going through all the calculation. Finally, the ammonia test showed that there should be five ammonia ligands. All of these four experiments along with outside sources showed that the cobalt(III) coordination compound S should be Pentaamminefluorocobalt(III) nitrate monohydrate, [Co(NH3)5F](NO3)2•H2O.
Introduction Dealing with the synthesis of one known cobalt(III) coordination compound (Q), [Co(NH3)6]Cl3 and an unknown cobalt compound (S), this lab performed four characterization tests to identify the unknown compound S. At the same time, this lab also familiarized some general coordination compound chemistry and the theory behind with freshman chemistry undergraduates. Dated back to the ancient Perisans and Egyptians, coordination compound has its history of bright red alizarin dye, which is a calcium aluminum chelate complex of hydroxyanthraquinone. In sixteen centry, Andreas Libavius recorded the first scientifically observation of a complete inorganic coordination compound. Later comes the key breakthrough that Co(III) bears six ligands in an octahedral geometry was carried out by Alfred Werner who had brought coordination compound chemistry to a new chapter. He also suggested the presence of isomers and how they could affect a compound. Nowadays, scientists have a much better understanding of important vitamins like B12 and the hemoglobin in blood with the knowledge of coordination compounds which greatly advanced health and medicine fields in today's world. A study of the trans-dioximines of cobalt(III), [CoX(Dioxim)2GuR]•nH2O, was carried out by Dranka et al1 to understand the heat stability of complexes and the thermolysis mechanism, along with the influence of other ligands nature and method of coordination on the durability of complexes which are analogies of vitamin B12 or can be used as catalysts. The overall analysis showed that the nature of equatorial and axial organic ligands decided the beginning of the decomposition under low temperature.1 Therefore, the identification decomposition temperature can be used to determine different bond isomers. Such temperature dependent characteristic can also be found in this lab when synthesizing cobalt compounds, so water bath was prepared to avoid rapid temperature changes during the synthesizes. Formed by a transition metal that acts as a Lewis acid and one or more types electron donors bonded to the central metal atom (or ion) by coordinate covalent bands, coordination compounds can be used in photography, electroplating of silver, and even estimating Ca2+ and Mg2+ in hard waterﾧ. To chemists, the structure of coordination compounds is very important in order to understand the reactions that occur with cobalt. Generally there are two parts of a coordination compound, one being the coordination sphere
