Inorganic Chemistry Assignment A) Assignment Guidelines Module Le...

Lab report for synthesis of a Synthesis of Cobaloxime
Abstract
This laboratory experiment was focus on the synthesis and characterization of Cobaloxime and subsequent introduction of the alkyl (ethyl) group through the intermediate formation of nucleophilic Co(I) which then expelled the I- anion from EtI in SN2 manner. This excersize exposed the students with advanced coordination chemistry, organometallic chemistry, and their bioinorganic aspects. Unfortunately, less then half of the maximum yield (88%) was obtained.
Introduction
Introduction to Cobaloximes
Cobaloximes are a large family of octahedral Bis(dimethylglyoximato)cobalt(III) complexes, containing a coordinated pyridine derivative and various axial ligands. They are regarded as a simplified, stable and more accessible model compound of cobalamine (coenzyme B12), useful for analysing the cobalamins properties and mechanism of catalysis. The most important similarity between the two systems is the existence (cobalamine) and simple incorporation (cobaloximes) of explicit Co-alkyl bonds. In this experiment, we have synthesized and characterized (by means of 1H NMR spectra and IR spectra) ethyl derivative of cobaloxime.
Typical routes to forming Cobaloxime
Carbon cobalt bond can, most easily, be introduced in Cobaloximes by following on of the two accessible general strategies (see Schematic representation bellow).[1] First of these methods (, labelled as (1), which is also the method employed in this course) involves the generation of nucleophilic Co(I) reagent, that can participate in nucleophilic substitution reactions (for example, with alkylhalogenide). The Co(I) can be generated with a palate of reducing agents, and, for this experiment, NaBH4 is utilized. It is important to