Optically active iridium complexes with cyclopentadienyl-phosphine ligands: synthesis and oxidative addition of methyl iodide

The dimer [Ir(μ-Cl)(C8H14)2]2 reacts with the ligands (S)-(C5H4CH2CH(Ph)PPh2)Li and (R)-(C5H4CH(Cy)CH2PPh2)Li to give (S)-[Ir(η5-C5H4CH2CH(Ph)PPh2-κP)(C8H14)] and (R)-[Ir(η5-C5H4CH(Cy)CH2PPh2-κP)(C8H14)], which upon treatment with CH3I at room temperature afford the cationic iridium(III) compounds (S,SIr)-[Ir(η5-C5H4CH2CH(Ph)PPh2-κP)(CH3)(C8H14)][I] as a single diastereomer, and (R)-[Ir(η5-C5H4CH(Cy)CH2PPh2-κP)(CH3)(C8H14)][I] as a 9:1 mixture of two diastereomers. If the oxidative addition reaction is performed at reflux in methylene chloride, the starting complexes convert to the neutral compounds (S)-[Ir(η5-C5H4CH2CH(Ph)PPh2-κP)(CH3)(I)] and (R)-[Ir(η5-C5H4CH(Cy)CH2PPh2-κP)(CH3)(I)] as 1.6:1 and 3.3:1 mixtures of diastereoisomers, respectively. Carbonyl iridium complexes are synthesized by reacting [IrCl(CO)(PPh3)2] with the ligands to afford (S)-[Ir(η5-C5H4CH2CH(Ph)PPh2-κP)(CO)] and (R)-[Ir(η5-C5H4CH(Cy)CH2PPh2-κP)(CO)]. They give upon treatment with CH3I the cationic species (S)-[Ir(η5-C5H4CH2CH(Ph)PPh2-κP)(CH3)(CO)][I] and (R)-[Ir(η5-C5H4CH(Cy)CH2PPh2-κP)(CH3)(CO)][I] as 1.6:1 and 3:1 mixture of diastereomers, respectively. No migratory-insertion of the methyl group into the carbonyl–metal bond has been observed even after prolonged heating.