On the Reactivity of Dihydridoirida-β-diketones with 2‑Aminopyridines. Formation of Acylhydrido Complexes with New PCN Terdentate Ligands

2-Aminopyridines (H₂NC₅H₃RN) react with [IrH₂{(PPh₂(<i>o</i>-C₆H₄CO))₂H}] (<b>1</b>) in refluxing methanol to afford [IrH­(PPh₂(<i>o</i>-C₆H₄CO))­(PPh₂(<i>o</i>-C₆H₄CHNHC₅H₃RN))] (R = H (<b>2</b>), R = CH₃ (<b>3</b>)) containing new terdentate PCN ligands in a facial disposition with the phosphorus atom <i>trans</i> to H and the new alkyl fragment <i>trans</i> to the other phosphorus atom. The formation of <b>2</b> and <b>3</b> requires imination of the hydroxycarbene moiety in <b>1</b>, iridium to carbon hydrogen transfer, and coordination of the nitrogen atom of pyridine to iridium. In refluxing methanol the reaction of <b>1</b> with the N-substituted 2-(methylamino)­pyridine leads to [IrH­(PPh₂(<i>o</i>-C₆H₄CO))­(PPh₂(<i>o</i>-C₆H₄C­(OH)­N­(CH₃)­C₅H₄N))] (<b>4</b>), containing a PCN ligand with a hydroxyalkyl moiety <i>trans</i> to phosphorus and the nitrogen atom of pyridine <i>trans</i> to hydride. By performing this reaction in the presence of KOH, complex [IrH­(PPh₂(<i>o</i>-C₆H₄CO))­(PPh₂(<i>o</i>-C₆H₄C­(OCH₃)­N­(CH₃)­C₅H₄N))] (<b>5</b>), with a methoxyalkyl moiety in the PCN ligand and similar stereochemistry to that of <b>2</b> and <b>3</b>, is obtained. In chloroform solution <b>5</b> transforms, with retention of the stereochemistry, into [IrH­(PPh₂(<i>o</i>-C₆H₄CO))­(PPh₂(<i>o</i>-C₆H₄C­(OH)­N­(CH₃)­C₅H₄N))] (<b>6</b>), an isomer of <b>4</b>. Formation of complexes <b>4</b>–<b>6</b> is proposed to occur via OH----HIr hydrogen bond formation and hydrogen evolution. Single-crystal X-ray diffraction analysis was performed on <b>3</b>, <b>4</b>, <b>5</b>, and <b>6