Synthesis of Silver(I) and Gold(I) Complexes Containing Enantiopure Pybox Ligands. First Assays on the Silver(I)-Catalyzed Asymmetric Addition of Alkynes to Imines

Dinuclear complexes [Ag<sub>2</sub>(CF<sub>3</sub>SO<sub>3</sub>)­{(<i>S</i>,<i>S</i>)-<sup><i>i</i></sup>Pr-pybox}<sub>2</sub>]­[CF<sub>3</sub>SO<sub>3</sub>] (<b>1</b>), [Ag<sub>2</sub>(R-pybox)<sub>2</sub>]­[X]<sub>2</sub> [R-pybox = 2,6-bis­[4-(<i>S</i>)-isopropyloxazolin-2-yl]­pyridine (<i>S</i>,<i>S</i>)-<sup><i>i</i></sup>Pr-pybox and X = PF<sub>6</sub> (<b>2</b>) and BF<sub>4</sub> (<b>3</b>); R-pybox = 2,6-bis­[(3a<i>S</i>,8a<i>R</i>)-8,8a-dihydro-3a<i>H</i>-indeno­[1,2-<i>d</i>]­oxazol-2-yl]­pyridine (3a<i>S</i>,3a′<i>S</i>,8a<i>R</i>,8a′<i>R</i>)-indane-pybox and X = CF<sub>3</sub>SO<sub>3</sub> (<b>4</b>)], [Ag<sub>2</sub>{(<i>S</i>,<i>S</i>)-<sup><i>i</i></sup>Pr-pybox}­{(3a<i>S</i>,3a′<i>S</i>,8a<i>R</i>,8a′<i>R</i>)-indane-pybox}]­[CF<sub>3</sub>SO<sub>3</sub>]<sub>2</sub> (<b>5</b>), and [Ag<sub>2</sub>(R-pybox)<sub>3</sub>]­[X]<sub>2</sub> [R-pybox = (3a<i>S</i>,3a′<i>S</i>,8a<i>R</i>,8a′<i>R</i>)-indane-pybox and X = CF<sub>3</sub>SO<sub>3</sub> (<b>10</b>), SF<sub>6</sub> (<b>11</b>), and PF<sub>6</sub> (<b>12</b>)] as well as mononuclear complexes [Ag­(R-pybox)<sub>2</sub>]­[X] [R-pybox = (<i>S</i>,<i>S</i>)-<sup><i>i</i></sup>Pr-pybox and X = SbF<sub>6</sub> (<b>6</b>), PF<sub>6</sub> (<b>7</b>), and BF<sub>4</sub> (<b>8</b>); R-pybox = (3a<i>S</i>,3a′<i>S</i>,8a<i>R</i>,8a′<i>R</i>)-indane-pybox) and X = BF<sub>4</sub> (<b>9</b>)] have been prepared by the reaction of the corresponding silver salts and pybox ligands using the appropriate molar ratio conditions. The first gold­(I)/pybox complex [Au<sub>6</sub>Cl<sub>4</sub>{(<i>S</i>,<i>S</i>)-<sup><i>i</i></sup>Pr-pybox}<sub>4</sub>]­[AuCl<sub>2</sub>]<sub>2</sub> (<b>13</b>) has been synthesized by the reaction of [AuCl­{S­(CH<sub>3</sub>)<sub>2</sub>}] and (<i>S</i>,<i>S</i>)-<sup><i>i</i></sup>Pr-pybox (1:1 molar ratio) in acetonitrile. The structures of the dinuclear (<b>1</b>, <b>4</b>, <b>5</b>, <b>10</b>, and <b>11</b>) and mononuclear (<b>6</b> and <b>9</b>) silver complexes and the hexanuclear gold complex <b>13</b> have been determined by single-crystal X-ray diffraction analysis. These studies have been complemented with a solution-state study by NMR spectroscopy, which included structure elucidation, variable-temperature measurements, and diffusion studies using diffusion-ordered spectroscopy (DOSY; for complexes <b>1</b>, <b>4</b>, <b>10</b>, and <b>12</b>). Complexes <b>1</b>, <b>2</b>, <b>4</b>, and <b>10</b> have been assayed as catalysts in the asymmetric addition of phenylacetylene to <i>N</i>-benzylideneaniline.