trans–[Pr(NCBuᵗ)₂(Cp*₃)]

For C₃ᵥ [M(X)(Cp)₃]^n⊕ type structures the following applies but additional work is needed to see whether this is relevant to this molecule which is a D_3h. The three cyclopentadienyl groups as a set contribute 13 electrons rather than 15 (five for each cyclopentadienyl) to the metal. This is because one of the ligand orbitals set associated with the three cyclopentadienyl groups has no symmetry match with relevant metal atomic orbitals. This reduces the formal metal electron count by two. See:

• L.T. Reynolds and G. Wilkinson, J. Inorg. Nucl. Chem., 1956, 2, 246-253, https://doi.org/10.1016/0022-1902(56)80051-1. See contribution by W. Moffitt starting on page 248.
• J.W. Lauher and R. Hoffmann, J. Am. Chem. Soc. 1976, 98, 1729-1742, https://pubs.acs.org/doi/pdf/10.1021/ja00423a017
• B.E. Bursten, L.F. Rhodes, and R.J. Strittmatter, J. Am. Chem. Soc. 1989, 111, 2756-2758, https://pubs.acs.org/doi/pdf/10.1021/ja00190a002
• B.E. Bursten and R.J. Strittmatter, Angew. Chem., Int. Ed. Engl., 1991, 30, 1069–1085, https://doi.org/10.1002/anie.199110691
• Synthesis, Structure, and Reactions of (η⁵-C₅H₅)₃Zr", Organometallics, 1995, 14, 3435–3439, https://pubs.acs.org/doi/abs/10.1021/om00007a050