Fluoro(nitrile)xenon(<scp>II</scp>) cations, RCN–XeF<sup>+</sup>AsF<sub>6</sub>–(R = H, CH<sub>3</sub>, CH<sub>2</sub>F, C<sub>2</sub>H<sub>5</sub>, C<sub>2</sub>F<sub>5</sub>, C<sub>3</sub>F<sub>7</sub>, or C<sub>6</sub>F<sub>5</sub>); novel examples of xenon–nitrogen bonds and<sup>129</sup>Xe–<sup>13</sup>C,<sup>129</sup>Xe–<sup>1</sup>H, and<sup>129</sup>Xe-<sup>14</sup>N nuclear spin-spin couplings