Synthesis and Structure of a Zirconium Dinitrogen Complex with a Side-On Bridging N₂ Unit

Reduction of Zr(O-2,6-Me2C6H3)Cl2[N(SiMe2CH2PPri2)2] with sodium amalgam under dinitrogen yields the dinuclear zirconium dinitrogen complex {[(Pri2PCH2SiMe2)2N]Zr(O-2,6-Me2C6H3)}2(μ-η2:η2-N2). Solid state structural analysis shows that the dinitrogen unit is bound in a side-on mode of coordination with the N−N bond distance at 1.528(7) Å; resonance Raman spectra show a band at 751 cm-1 for ν(N−N), which is consistent with this very long bond. In addition, the N2 ligand is hinged slightly so that the Zr2(μ-η2:η2-N2) core adopts a flattened butterfly shape rather than a completely planar core as found in other related systems. Other Zr(IV) precursors of the general formula ZrCl2X[N(SiMe2CH2PPri2)2] (X = OBut, OCHPh2, NPh2) either decompose upon reduction under N2 or produce mixtures of products.