To a beaker add 48 g of thallium(I) sulfate, 20.2 g of potassium hydroxide dissolved in 400 mL of very cold water with stirring. Then with vigorous stirring add 16.5 mL of fresh cyclopentadiene, stir for 10 minutes, filter, wash with some water and then with ice-cold methanol. Dry and sublimate the product in a vacuum.
The thallium salt solution
Addition of the cyclopentadiene
The dry product
The sublimated product