Stoichiometric homologation of 1,3-butadiene by reaction with the iridium methylene complex Ir=CH2[N(SiMe2CH2PPh2)2]

Article abstract of DOI:10.1021/om00009a028

The reaction of the iridium methylene complex Ir=CH₂[N(SiMe₂CH₂PPh₂)₂] with 1,3-butadiene leads to the formation of a new complex with the formula Ir(C₅H₈)[N(SiMe₂CH₂-PPh ₂)₂] in which 1 equiv of butadiene has been incorporated. By a series of NMR experiments, the structure was established as containing a σ-η³-pentenyl unit. The X-ray crystal structure confirms the stereochemistry of the hydrocarbyl unit as being anti-exo, with the tridentate ancillary ligand adopting the facial orientation. Labeling studies indicate that the formation is diastereoselective as a result of the orientation of the incoming double bond in the early stages of the reaction mechanism.