THE TEOF62-ANION - THE 1ST EXAMPLE OF A MULTIPLY-CHARGED, PENTAGONAL BIPYRAMIDAL, MAIN-GROUP ELEMENT AX5YZ SPECIES AND THE VIBRATIONAL-SPECTRA OF THE TEOF5-ANION

The new TeOF62- anion has been isolated in the form of its tetramethylammonium salt from solutions of N(CH3)4F and N(CH3)4TeOF5 in CH3CN. It was characterized by vibrational spectroscopy, a normal coordinate analysis and ab initio calculations. It is shown that its structure is analogous to that of the recently discovered, isoelectronic IOF6- anion which makes it only the second known representative.of a pentagonal bipyramidal, main-group element AX5YZ species and the first multiply charged example of such a species. The stretching force constant of the TeF5 part of TeOF62- is significantly smaller than that in IOF6- indicating that the additional negative charge in TeOF62-weakens mainly the equatorial Te-F bonds. The vibrational spectra of N(CH3)4TeOF5 are also reported, and the results of ab initio calculations and of a normal coordinate analysis of TeOF5- show that six of its fundamental vibrations had previously been assigned incorrectly.