In a long re-sealable ampule, 2-Y (4.290 g, 8.259 mmol) was heated to 120 °C in the solid state at ca. 0.01 mbar for 2 h, resulting in the partial sublimation of the solid material. After cooling to ambient temperature, the residues were found to have a mass of 3.699 g (8.270 mmol assuming the formula weight of 3-Y), consistent with the removal of 99.2% of the bound THF. The 1 H, 11 B, C and Si NMR spectra of this amorphous material were found to be identical to an authentic crystalline sample of 3-Y, prepared as follows. In a long re-sealable ampule, 2-Y (1.390 g, 2.676 mmol)