diphenylacetylene were stored in the glovebox. Additionally, (Z)-stilbene and mesitylene were degassed by three freeze-pump-thaw cycles before use. All the reactions were performed under an N2(g) atmosphere in the glovebox. Deuterated solvents were purchased from Cambridge Isotope Laboratory Inc. (Cambridge, USA), degassed by three freeze-pump-thaw cycles, and stored over molecular sieves before use. Common solvents were dried using a MBRAUN MB SPS-80 purification system and/or distillation technique. [( Ph bppe H,CHptol2 )Ni]N2 was synthetized according to literature procedure. Physical methods: 1 H, C and 31 P NMR spectra (400, 100, 376 and 161 MHz respectively) were recorded on an Agilent MR400 or a Varian AS400 spectrometer at 297 K unless it is stated differently. 1 H and C NMR chemical shifts relative to tetramethylsilane are referenced to the residual solvent resonance unless stated otherwise. Infrared spectra were recorded using a Perking Elmer Spectrum One FT-IR spectrometer under N2 flow. GC analyses were performed on a Perkin-Elmer Clarus 500 GC [column PE, Elite-5, 30m x 0.32 mm x 0.25 µm, (5% phenyl)-(95% methyl)polysiloxane)] and a flame-ionization detector (FID).