To a solution of 8-Hydroxyquinoline (5.44 g, 37.5 mmol) in ethanol (200 mL, 95%) was added hafnium (IV) chloride (3.0 g, 9.37 mmol) in ethanol (100 mL), followed by a further 300 mL water. The pH of the solution was increased by dropwise addition of piperidine until a yellow precipitate forms. The resulting yellow precipitate was collected and washed with ethanol (100 mL, 95%), water (200 mL) and finally ethanol (100 mL, 95%). The sample was dried under vacuum at 80° C. until no further weight loss was detected. Sublimation (400° C., 10−6 Torr) yielded an analytical sample (4.5 g, 64%), m.p. 398° C.
