Scheme 2. Generation, Structure and Protonation of Nickelacyclopropene 3.

(a) Steps Involved in the Initiation Pathway and in the Synthesis of the Nickelacyclopropene 3; (b) Molecular Structure of 3 Obtained by XRD (Front and Side Views; ORTEP; 50% Probability; H Atoms Omitted for Clarity; Color Code: Gray: C; Purple: N; Green: Ni); (c) Computed Electron Density of the HOMO of 3 (H Atoms Are Omitted for Clarity); (d) Protonation Reactions Starting from the Nickelacyclopropene 3; and (e) ¹H NMR Spectrum of the Vinyl Region of the Crude Mixture of 3 and BzOH (1 equiv) in DMF-d₇ with nBu₄NPF₆ (0.1 M).