Preparation of Triiodotris pyridine aluminum

A 500-mL, two-necked flask, fitted with a nitrogen inlet and outlet and a reflux condenser, is flushed with nitrogen and then charged with anhydrous diethyl ether (200 mL), pure aluminum turnings (3 g, 0.11 mole), and dry iodine (20 g, 0.078 mole). The mixture is boiled under reflux until the solution turns colorless (1-2 hr), while a slow stream of nitrogen is passed through it. The mixture is then filtered under nitrogen. 

The solution is stirred magnetically while 13 mL of freshly distilled pyridine is added dropwise. Heat is evolved and precipitation occurs quickly. The white precipitate is separated by filtration, washed twice with diethyl ether, and dried in vacuo. All operations are carried out in an inert atmosphere. 

The complex is obtained as a white microcrystalline solid that melts at 195-198° with decomposition. It is insoluble in most organic solvents but rather soluble in methanol. The product is moisture sensitive but remains unchanged after 2 years when stored in a tightly stoppered container in darkness. The infrared spectrum, taken as Csl pellet, has bands at 1630 (s), 1598 (vs), 1524 (s), 1478 (s), 1364 (w), 1330 (m), 1246 (m), 1238 (s), 1186 (m), 1152 (m), 1050 (s), 1026 (m), 988 (m), 740 (s), and 672 (vs) cm 1. 

Submitted by J. MacB. HARROWFIELD, A. J. HERLT, and A. M. SARGESON Checked by THEODORE Del DONNOt 

To a stirred solution of Li2C03 (25 g) in a solution of ( )-[Co(en)3]Cl3 (9.1 g, 0.025 mole) in water (125 mL) is added aqueous ammonia (166 mL, 2.5 mole) diluted to 502 mL and aqueous formaldehyde (592 mL, 38%, 7.5 mole). The solutions are added separately and dropwise over 2 hours using a peristaltic pump. The mixture is stirred for another 30 minutes, the Li2C03 is filtered off, and the pH of the filtrate is adjusted to 3 with 12 M HC1. The solution is diluted to 8 L and sorbed on an ion exchange column (Dowex 50-WX2,200-400 mesh, H+ form, 5X10 cm). The column is eluted with Na3citrate (5 L of 

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