Synthesis and Structure of a Zirconium Dinitrogen Complex with a Side-On Bridging N(2) Unit.

Reduction of Zr(O-2,6-Me(2)C(6)H(3))Cl(2)[N(SiMe(2)CH(2)PPr(i)(2))(2)] with sodium amalgam under dinitrogen yields the dinuclear zirconium dinitrogen complex {[(Pr(i)(2)PCH(2)SiMe(2))(2)N]Zr(O-2,6-Me(2)C(6)H(3))}(2)(&mgr;-eta(2):eta(2)-N(2)). 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 nu(N-N), which is consistent with this very long bond. In addition, the N(2) ligand is hinged slightly so that the Zr(2)(&mgr;-eta(2):eta(2)-N(2)) 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 ZrCl(2)X[N(SiMe(2)CH(2)PPr(i)(2))(2)] (X = OBu(t), OCHPh(2), NPh(2)) either decompose upon reduction under N(2) or produce mixtures of products.