1. Johnny Mackey
Chem 471
Independent Project Abstract
Independent Project
Cobaltis found in humans in trace amounts, however it is still considered biologically important. A deficiency of
cobalthas been linked to anemia1 in previous literature,and the synthesis of cobalamin’s areimportantfor study
in the lab.The link between vitamin B12 for which cobalamin isa coenzyme, is heavily correlated with anemia and
is of particular interestto hematologists2.The structure of methylcobalamin in which the alkyl group is a methyl
group is shown in figure 1.
Figure 1
Cobalamin-based enzymes catalyzetwo kinds of transformations,dependingon the identity of the alkyl ligand.The
molecular complexity of the cobalaminsmakes itdifficultto study the coordination chemistry of the cobaltcenter.
The reaction apparatus consisted of a 200-mL round bottom flask and a pressureequalizingaddition funnel.One
neck was fitted with an Argon gas inlet to prevent air exposure.The inletwas charged with 4g CoCl 2-6H2O and 4g
of dimethylglyoxime in 75 mL of methanol. The structure of dimethylglyoxime is shown in figure 2, and the exact
results and yields arerecorded in table1. NaOH and pyridinewere added dropwiseover 20 minutes, whilecooling
the apparatus in ice.NaBH4 was then added to the cold reaction mixture and became a dark orange as Co(dmgH)2
was formed. 2-bromopropane was added in 1 mL increments to approximately 2.25 mL and stirred for a further 40
minutes in an icebath again.Final productwas collected by filtration and dried under filtration several times.
Figure 2
Compound Actual Theoretical Percent Yield
Dimethylglyoxime 4.000g NA NA
Co(dmgH)2(py) 9.4231 9.9980 94.25%
Table 1
Two dimethylglyoximate(dmgH-) ligands can link through hydrogen bonds to form planar anionicmacrocycle
molecules that bind cobaltthrough its four nitrogen atoms. This experiment will began with the preparation of
Co(dmgH)2(py)2. Reduction of this complex with BH4
- produces a cobalt(I) derivativewith a molecular formula of
Co(dmgH)2(py) which is a highly nucleophilic complex thatreacts with alkyl halides to give cobalt(III) alkyl
complexes. We will usealkylatingisopropyl bromideas our halide:
Co(dmgH)2(py)2 + NaBH4  Na[Co(dmgH)2(py)] + BH3  py + ½ H2
Na[Co(dmgH)2(py)2] + BrCH(CH3)2  Co[CH(CH3)2](dmgH)2(py) + NaBr
Which structureis shown below in figure 33.

2. Johnny Mackey
Chem 471
Independent Project Abstract
Figure 3
Where R is pyridine, and B is isopropyl. Grignard reagents can also be used, however it requires 3 mols of the
Grignard reagent, and will only be performed if necessary and if time permits, and in the experiment the reaction
mixture was found to be reactive and most of the product was lost to air exposure because of an incomplete reaction
during the Grignard reagents step.In the next step of the experiment, chloride is added to remove the alkyl group to
give CoCl(dmgH)2(py) shown below:
CoR(dmgH)2(py) + Cl2  RCl + CoCl(dmgH)2(py)
The last step was supposed to be to convert CoCl(dmgH)2(py) to its phenyl derivative Co(C6H5)(dmgH)2(py), which
has been published in various Inorganic Synthesis journals for it’s potential study and use4.IR of Co(dmgH)2(py) is
included.
References
1.) Biological Research for Nursing, Volume 17, Issue4,Pages444-454,Journal,2015
2.) Andres, E., Federici, L., Kaltenbach, G., Maloisel, F.; Hematologie, Volume 13, Issue3,Pages186-192,
Journal;General Review, 2007
3.) http://www.chm.bris.ac.uk/motm/vitaminb12/cobaloximes/expt4.htm
4.) Schrauzer, G. N.; Inorganic Syntheses, Volume 11,pages 61-70,Journal,1968