Bowl vs Saddle Conformations in Cyclononatriene-Based Anion Binding Hosts

The synthesis of organometallic complexes [{Ru(<i>p</i>-MeC<sub>6</sub>H<sub>4</sub>CHMe<sub>2</sub>)}<i><sub>n</sub></i>(C<sub>21</sub>H<sub>24</sub>S<sub>3</sub>)][CF<sub>3</sub>SO<sub>3</sub>]<sub>2</sub><i><sub>n</sub></i> (<i>n</i> = 1, <b>6</b>; <i>n</i> = 2, <b>7</b>) and [{Ir(C<sub>5</sub>Me<sub>5</sub>)}<sub>2</sub>(C<sub>21</sub>H<sub>24</sub>S<sub>3</sub>)][CF<sub>3</sub>SO<sub>3</sub>]<sub>4</sub> (<b>9</b>) based upon the trimeric macrocycle cyclotris(dimethylthiophenylene) (<b>4</b>) is reported. A saddle conformation is identified for the free ligand <b>4</b> and complexes <b>6</b> and <b>9</b> by X-ray crystallography. The anion complexation behavior of complex <b>9</b> is compared with the related cyclotriveratrylene complex [{Ru(<i>p</i>-MeC<sub>6</sub>H<sub>4</sub>CHMe<sub>2</sub>)}<sub>2</sub>(C<sub>27</sub>H<sub>30</sub>O<sub>6</sub>)][CF<sub>3</sub>SO<sub>3</sub>]<sub>4</sub> (<b>2</b>), which possesses a bowl-shaped conformation, by <sup>1</sup>H NMR titration studies in a variety of solvents. While host <b>2</b> displays a significant affinity for halides with binding constants of up to 1.25(7) × 10<sup>3</sup> M<sup>-1</sup> in nitromethane solution, the absence of a molecular cavity in <b>9</b> results in very little specific anion affinity. The 1,3-alternate calix[4]arene complex [{Ru(η<sup>6</sup>-<i>p-</i>MeC<sub>6</sub>H<sub>4</sub>CHMe<sub>2</sub>)}<sub>2</sub>(η<sup>6</sup>:η<sup>6</sup>-C<sub>40</sub>H<sub>48</sub>)][BF<sub>4</sub>]<sub>4</sub> (<b>11</b>) is also reported and shown to bind anions in an unusual C−H···anion hydrogen-bonding fashion by X-ray crystallography and <sup>1</sup>H NMR.