<jats:title>Abstract</jats:title><jats:p>The iridium(<jats:sc>I</jats:sc>) complexes [Ir(CO)(κ<jats:sup>3</jats:sup>‐<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>‐R‐pybox)][PF<jats:sub>6</jats:sub>] [R‐pybox = (<jats:italic>S</jats:italic>,<jats:italic>S</jats:italic>)‐<jats:italic>i</jats:italic>Pr‐pybox (<jats:bold>1</jats:bold>), (<jats:italic>R</jats:italic>,<jats:italic>R</jats:italic>)‐Ph‐pybox (<jats:bold>2</jats:bold>)] have been prepared by reaction of their precursor complexes [Ir(η<jats:sup>2</jats:sup>‐C<jats:sub>2</jats:sub>H<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>(κ<jats:sup>3</jats:sup>‐<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>‐R‐pybox)][PF<jats:sub>6</jats:sub>] (R = <jats:italic>i</jats:italic>Pr or Ph) with carbon monoxide. The analogous carbonylrhodium(<jats:sc>I</jats:sc>) complexes [Rh(CO)(κ<jats:sup>3</jats:sup>‐<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>‐R‐pybox)][PF<jats:sub>6</jats:sub>] [R‐pybox = (<jats:italic>S</jats:italic>,<jats:italic>S</jats:italic>)‐<jats:italic>i</jats:italic>Pr‐pybox (<jats:bold>3</jats:bold>), (<jats:italic>R</jats:italic>,<jats:italic>R</jats:italic>)‐Ph‐pybox (<jats:bold>4</jats:bold>)] have been synthesised by reaction of [Rh(μ‐Cl)(η<jats:sup>2</jats:sup>‐C<jats:sub>2</jats:sub>H<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub>]<jats:sub>2</jats:sub>, carbon monoxide, R‐pybox and NaPF<jats:sub>6</jats:sub>. Complexes <jats:bold>1</jats:bold>–<jats:bold>4</jats:bold> undergo oxidative addition reactions with iodine and CH<jats:sub>3</jats:sub>I leading, with high stereoselectivity, to the complexes [MI(X)(CO)(κ<jats:sup>3</jats:sup>‐<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>‐R‐pybox)][PF<jats:sub>6</jats:sub>] [M = Ir, R = <jats:italic>i</jats:italic>Pr, X = I (<jats:bold>5</jats:bold>); M = Rh, R = <jats:italic>i</jats:italic>Pr, X = I (<jats:bold>6</jats:bold>); M = Rh, R = Ph, X = I (<jats:bold>7</jats:bold>); M = Ir, R = <jats:italic>i</jats:italic>Pr, X = CH<jats:sub>3</jats:sub> (<jats:bold>8</jats:bold>); M = Ir, R = Ph, X = CH<jats:sub>3</jats:sub> (<jats:bold>9</jats:bold>); M = Rh, R = <jats:italic>i</jats:italic>Pr, X = CH<jats:sub>3</jats:sub> (<jats:bold>10</jats:bold>); M = Rh, R = Ph, X = CH<jats:sub>3</jats:sub> (<jats:bold>11</jats:bold>)]. The treatment of complexes <jats:bold>1</jats:bold> and <jats:bold>2</jats:bold> with HCl, allyl chloride or acyl chloride results, in most cases, in the stereoselective formation of the iridium(<jats:sc>III</jats:sc>) complexes [IrHCl(CO)(κ<jats:sup>3</jats:sup>‐<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>‐R‐pybox)][PF<jats:sub>6</jats:sub>] [R = <jats:italic>i</jats:italic>Pr (<jats:bold>12</jats:bold>), Ph (<jats:bold>13</jats:bold>)], [IrCl(η<jats:sup>1</jats:sup>‐CH<jats:sub>2</jats:sub>CH=CH<jats:sub>2</jats:sub>)(CO)(κ<jats:sup>3</jats:sup>‐<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>‐R‐pybox)][PF<jats:sub>6</jats:sub>] [R = <jats:italic>i</jats:italic>Pr (<jats:bold>14</jats:bold>), Ph (<jats:bold>15</jats:bold>)] or [IrCl{η<jats:sup>1</jats:sup>‐C(O)CH<jats:sub>3</jats:sub>}(CO)(κ<jats:sup>3</jats:sup>‐<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>,<jats:italic>N</jats:italic>‐R‐pybox)][PF<jats:sub>6</jats:sub>] [R = <jats:italic>i</jats:italic>Pr (<jats:bold>16</jats:bold>), Ph (<jats:bold>17</jats:bold>)], respectively. The structures of derivatives <jats:bold>10</jats:bold> and <jats:bold>15</jats:bold> have been determined by single‐crystal X‐ray diffraction analysis. The catalytic activity of monocarbonylrhodium(<jats:sc>I</jats:sc>) and ‐iridium(<jats:sc>I</jats:sc>) complexes <jats:bold>1</jats:bold> and <jats:bold>3</jats:bold> in the hydrosilylation and dehydrosilylation of acetophenone with diphenylsilane has also been examined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)</jats:p>