Molecular Zirconium Nitride Super Base from a Mononuclear Parent Imide

In this work, we prepared, isolated, and structurally characterized a zirconium complex having a terminally bound imide motif, (PN)₂Zr≡NH (PN^- = (N-(2-ⁱPr₂P-4-methylphenyl)-2,4,6-trimethylanilide)), along with the zirconium nitride complex {(PN)₂Zr≡N[μ₂-Li(THF)]}₂. (PN)₂Zr≡NH was prepared by reduction of trans-(PN)₂Zr(N₃)₂ with KC₈. Isotopic labeling and spectroscopic studies were conducted using the respective ¹⁵N enriched isotopologues, whereas solid-state structural studies confirmed some of the shortest Zr≡N distances known to date (Zr≡NH, 1.830(3) Å; Zr≡N^-, 1.822(2) Å). It was found that the nitride in {(PN)₂Zr≡N[μ₂-Li(THF)]}₂ is super basic and in the range of -36 to -43 p K_b units. Computational studies have been applied to probe the bonding and structure for this new class of zirconium-nitrogen multiple bonds.