Dinuclear titanium dialkyl complexes bridged by two μ-arylimido ligands, [CpTi(CH SiMe )(μ-NAr)] (Cp=cyclopentadienyl) activated an ortho-aryl C-H bond of an μ-arylimido ligand to form a four-membered titanacycle. The subsequent insertion reaction of 1-(trimethylsilyl)propyne into a metal-carbon bond of the four-membered titanacycle yielded the corresponding six-membered titanacycle. Further ortho-C-H bond activation of the other μ-arylimido ligand and an insertion reaction proceeded to give dinuclear titanium complexes with two six-membered titanacycles. An Eyring plot in the temperature range 130-150 °C revealed activation parameters for the alkenylation reaction, and deuterium-labeling experiments showed that the C-H bond activation step is the rate determining step. Relative Gibbs free energies of the starting complexes, reaction intermediates, and transition states were calculated by using DFT calculations.

ortho‐C−H bond alkenylation proceeded at N‐arylimido ligands bridging two titanium metal centers, in which the Ti2N2 four‐membered core was flexibly twisted to form the appropriate conformation for both ortho‐C−H bond activation and insertion reactions of the internal alkyne to give six‐membered titanacycles. Kinetic studies, deuterium‐labeling experiments, and computational studies revealed the reaction mechanism. More information can be found in the Full Paper by H. Tsurugi, K. Mashima et al. on page 586 ff.