The dinitrogen complex [Zr 2 ( 5 -Cp*) 4 (N 2 ) 3 ] has been isolated

The dinitrogen complex [Zr₂(η⁵-Cp*)₄(N₂)₃] has been isolated and its structure determined by single-crystal X-ray diffraction. Each Zr atom is bonded to two Cp* and one terminal N₂. The third N₂ bridges between the Zr atoms in a nearly linear ZrNNZr array. Before consulting the reference, write a plausible structure for this compound that accounts for the ¹H-NMR spectrum obtained on a sample held at 27°C. This spectrum shows two singlets, indicating that the Cp* rings are in two different environments. At somewhat above room temperature these rings become equivalent on the NMR timescale and ¹⁵N-NMR indicates that N₂ exchange between the terminal ligands and dissolved N₂ is correlated with the process that interconverts the Cp* ligand sites. Propose a way in which this equilibration could interconvert the sites of the Cp* ligands.