Insertion of nitriles into a zirconium-iridium heterobimetallic complex: Amechanistic study

The reaction of Cp2Zr(mu-N-Bu-t)IrCp* (1) with nitriles (RC=N) yields the c yclometalated species Cp2Zr(mu-N-Bu-t)(mu-NC(H)(R)CH(2-)eta(5)-C5Me4)Ir (R = C6H5 (2a), o-Et-C6H4 (2b), (p-CH3)-C6H4 (2c), (p-CF3)C6H4 (2d), (p-MeO)C6 H4 (2e), cyclopropyl (2f), CH(Me)(2) (2g), NC(CH2)(3) (2h)). An intermediat e is observed in the reaction of 1 with cyanocyclopropane. This intermediat e has been characterized by NMR spectroscopy as a tetramethylfulvene comple x with a bridging alkylidene-amido moiety, Cp2Zr(mu-N-Bu-t)(mu-NCRH)(eta(5) -C5Me4CH2)Ir (R = cyclopropyl; 3). Kinetic simulations were performed and p rovided evidence that the intermediate is productive. The reaction of 1 wit h 2-arylacetonitriles yields two noninterconvertible complexes: a cyclometa lated species (4), analogous to complex 2, and the new olefinic species Cp2 Zr(mu-N-Bu-t)(mu-N-CHCH(R)IrCp* (R = C6H5 (5a), R = (p-CF3)C6H4 (5b), R = ( p-MeO)C6H4 (5c)). The reaction pathways for the formation of both 4 and 5 p roceed through the fulvene complex 3; however, the product ratio 5:4 was fo und to be dependent upon the reaction conditions.