STOICHIOMETRIC HOMOLOGATION OF 1,3-BUTADIENE BY REACTION WITH THE IRIDIUM METHYLENE COMPLEX IR=CH2[N(SIME(2)CH(2)PPH(2))(2)]

The reaction of the iridium methylene complex Ir=CH2[N(SiMe(2)CH(2)PPh (2))(2)] with 1,3-butadiene leads to the formation of a new complex wi th the formula Ir(C5H8)[N(SiMe(2)CH(2)PPh(2))(2)] in which 1 equiv of butadiene has been incorporated. By a series of NMR experiments, the s tructure was established as containing a sigma-eta 3-pentenyl unit. Th e X-ray crystal structure confirms the stereochemistry of the hydrocar byl unit as being anti-exo, with the tridentate ancillary ligand adopt ing the facial orientation. Labeling studies indicate that the formati on is diastereoselective as a result of the orientation of the incomin g double bond in the early stages of the reaction mechanism.