Oxidation of germanium(II) azides with HN3: a convenient route to six-co-ordinate triazidogermanium(IV) compounds

Abstract

Reaction of GeCl₂(C₄H₈O₂) 1 with NaL_OEt [L_OEt = (C₅H₅)Co{P(O)(OEt)₂}₃] gave L_OEtGeCl 2, which reacts with NaN₃ to afford the germanium(II) azide L_OEtGeN₃3. A dissociation equilibrium between 3 and the ions [L_OEtGe]⁺ and N₃⁻ exists in solution, which is strongly dependent on the solvent polarity. Dissociation into ions is observed in solution for a variety of other four-co-ordinate germanium(II) azides bearing an anionic tridentate ligand. The crystal structures of 2 and 3 revealed a pseudo trigonal-bipyramidal co-ordination geometry around the germanium atom and an unsymmetric bonding of the L_OEt ligand with one long Ge–O_ax and two considerably shorter Ge–O_eq bonds. The structural data are compared with those of other four-co-ordinate germanium(II) chlorides and azides indicating the presence of a polar Ge–X bond (X = Cl or N₃) in 2 and 3. Oxidation of 3 with two equivalents of HN₃ gave selectively the six-co-ordinate triazidogermanium(IV) compound L_OEtGe(N₃)₃4. Similarly, oxidation of the germanium(II) azide Tp′GeN₃5 [Tp′ = HB(3,5-Me₂pz)₃, 3,5-Me₂pz = 3,5-dimethylpyrazol-1-yl] with HN₃ affords selectively Tp′Ge(N₃)₃6. The crystal structures of 4 and 6 have been determined and are compared with those of other six-co-ordinate germanium(IV) polyazides.