Figure 4. Mass spectrometry of intermediate species.

(a) ESI-MS spectra of the RT/24 h (1, Intermediate 1) and 130 °C/30 min (2, Intermediate 2) samples. For the former mixture, fragments in the region of m/z 900–1,500 were not detected, suggesting that Cd—Te covalent bonds did not form for the Intermediate 1 stage. For the latter sample, five groups of Cd_xTe_y fragments were detected, dominated by Cd₆Te₂, Cd₇Te₂, Cd₇Te₃, Cd₆Te₅ and Cd₇Te₅ (labelled by star symbols at m/z 929, 1,041, 1,169, 1,316 and 1,428, respectively). Close examination of the five groups of Cd_xTe_y fragments (x+y=8 (b), 9 (c), 10 (d), 11 (e) and 12 (f)) reveals the presence of both Cd and Te isotopes, suggesting the formation of Cd—Te covalent bonds for the Intermediate 2 stage. Possible skeletons (drawn by ChemOffice) for Cd₆Te₂ (g) and Cd₇Te₂ (h) are suggested.