Preparation of a Typical Iron Slurry

Very often the piece of lithium coats with the metal powder. In such cases, the argon flow is increased, and, with a curved spatula, the piece of lithium is rubbed against the side of the flask to expose a fresh surface of the lithium. 

An iron slurry is prepared in the usual manner and then allowed to settle. The solvent above the slurry is removed (most of the iron is coated about the magnetic stirring bar), and the slurry is cooled to 0°C for the slow addition of 1 equiv of CeFsI per iron. After the addition, the flask is allowed to warm to rt and the brown mixture in the flask is stirred for 25 h even though the reaction appears to be complete in about 2 h. A slow stream of CO (large excess) is then bubbled through the thick brown solution for 11 h no color change is apparent. 

The volatiles are removed from the mixture under vacuum. The product is dissolved in 20 ml of CH2CI2 and then anaerobically filtered. Slow solvent evaporation in an inert atmosphere results in large yellow crystals. The crystals are often covered with a brown tarry residue which is readily removed by washing the crystals with a small amount of 2 1 hexane/CH2Cl2 mixture. (Yield 60% mp 103-114°C (sealed tube). Anal. Calcd for C22H2oFioFe06 C, 42.19 H, 3.22  

The analogous reaction carried out at about 55°C between an iron slurry and 1 equiv of CeFsBr, followed by bubbling a large excess of CO into the mixture, results in the same product and in comparable yield. Because of less tarry residues and hence easier workup, we find the reaction employing CeFsBr more attractive. 

3 Rieke, R.D. Kavaliunas, A.V. Organometallic Synthesis-, Elsevier Science Publishers B.V. Amsterdam, 1988 Vol. 4. 

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