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

Abstract

The dimer [Ir(μ-Cl)(C 8H 14) 2] 2 reacts with the ligands ( S)-(C 5H 4CH 2CH(Ph)PPh 2)Li and ( R)-(C 5H 4CH(Cy)CH 2PPh 2)Li to give ( S)-[Ir(η 5-C 5H 4CH 2CH(Ph)PPh 2-κ P)(C 8H 14)] and ( R)-[Ir(η 5-C 5H 4CH(Cy)CH 2PPh 2-κ P)(C 8H 14)], which upon treatment with CH 3I at room temperature afford the cationic iridium(III) compounds ( S, S Ir )-[Ir(η 5-C 5H 4CH 2CH(Ph)PPh 2-κ P)(CH 3)(C 8H 14)][I] as a single diastereomer, and ( R)-[Ir(η 5-C 5H 4CH(Cy)CH 2PPh 2-κ P)(CH 3)(C 8H 14)][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(η 5-C 5H 4CH 2CH(Ph)PPh 2-κ P)(CH 3)(I)] and ( R)-[Ir(η 5-C 5H 4CH(Cy)CH 2PPh 2-κ P)(CH 3)(I)] as 1.6:1 and 3.3:1 mixtures of diastereoisomers, respectively. Carbonyl iridium complexes are synthesized by reacting [IrCl(CO)(PPh 3) 2] with the ligands to afford ( S)-[Ir(η 5-C 5H 4CH 2CH(Ph)PPh 2-κ P)(CO)] and ( R)-[Ir(η 5-C 5H 4CH(Cy)CH 2PPh 2-κ P)(CO)]. They give upon treatment with CH 3I the cationic species ( S)-[Ir(η 5-C 5H 4CH 2CH(Ph)PPh 2-κ P)(CH 3)(CO)][I] and ( R)-[Ir(η 5-C 5H 4CH(Cy)CH 2PPh 2-κ P)(CH 3)(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.