The fluoro(perfluoroalkylnitrile)noble-gas(<scp>II</scp>) cations, R<sub>F</sub>CN–NgF<sup>+</sup>(Ng = Kr or Xe; R<sub>F</sub>= CF<sub>3</sub>, C<sub>2</sub>F<sub>5</sub>, n-C<sub>3</sub>F<sub>7</sub>), and the fluoro(trifluoro-s-triazine)xenon(<scp>II</scp>) cation, s-C<sub>3</sub>F<sub>3</sub>N<sub>2</sub>N–XeF<sup>+</sup>; novel noble gas–nitrogen bonds