Preparation from the Pyridinium Salt

Twenty grams of cobalt(II) carbonate (0.168 mol) and 150 ml. of c.p. pyridine (1.86 mols) are placed in a 500-ml. stainless-steel autoclave (synthesis 54). The autoclave is flushed three times with carbon monoxide at a pressure of 200 p.s.i. An equimolar mixture of carbon monoxide and hydrogen is admitted to a pressure of 3500 p.s.i. The rocking mechanism is started, and the temperature is raised to 155 to 160° and maintained in this range for 2 hours. The vessel is then allowed to cool to room temperature, and the gases are vented. The solution in the bomb contains about 2.5 g. of the pyridinium salt of the cobalt tetracarbonyl anion per 10 ml. (yield about 90%)4 

This solution is so diluted with pyridine that each 20 ml. contains 2.9 g. of the salt. The carbonyl hydride is then prepared as outlined in procedure A. The over-all yield is 20 to 23 g. (69 to 80%). 

Certain of the properties of cobalt tetracarbonyl hydride have been summarized previously.4 The pure compound decomposes thermally by a second-order process5 to hydrogen and dicobalt octacarbonyl. The compound is strongly 

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Finally, 2,4,6-tricyanophenol m.p. 185° has been prepared from 2,4,6-tris-carboxy-methyl-anisol by an analogous route. It is a strong acid (pk 1.0) which can only be prepared from the pyridinium salt to give the phenol by cation exchange with lewatit S 140147 >. 

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