The reaction of TeClF5 with CH3OH, and CH3OSiMe3, leads to a mixture of cis- and trans-(CH3O)TeClF4 in a ratio of 1:6, as well as some unidentified Te(IV) product. The vibrational spectrum of the 1:6 mixture of cis- and trans-(CH3O)TeClF4 was accounted for on the basis of the predominant pseudo-C4vtrans isomer. TeClF5 is unreactive towards anhydrous HF, SbF5, AlCl3, SO2, F2, and ClF at room temperature. Over the temperature range 70–250 °C it thermally decomposes to TeF6, TeF4, and Cl2. It slowly reacts with CsF to form CsTeF5, TeF6, Cl2, and small amounts of ClF, and with HNMe2 it is also reduced to form TeF4•HNMe2.