Organoamido- and Aryloxo-Lanthanoids, 19 Synthesis and Structures of cisoid and transoid Bis(1,2-dimethoxyethane)bis(#eta#~2-pyrazolato)lanthanoid(II) Complexes

摘要

The complexes [Yb(bind)_2(DME)_2], [Yb(MePhpz)_2(DME)_2], [Yb(azin)_2(DME)_2], and [Eu(Ph_2pz)_2(DME__2] (bindH = 4,5-dihydro-2H-benz[g]indazole; MePhpzH = 3-methyl-5-phenylpyrazole; azinH = 7-azaindole; Ph_2pzH = 3,5-diphenylpyrazole; DME = 1,2-dimethoxyethane) have been prepared by redox transmetallation between ytterbium or europium metal and the corresponding thallium(I) pyrazolate in tetrahydrofuran (THF) in the presence of mercury metal, followed by work up with DME. The thallium reagents were obtained by treatment of the appropriate pyrazole with thallium(I) ethoxide. Both [Yb(Ph_2pz)_2(DME)_2] and [Sm(Ph_2pz)_2(DME)_2] have been prepared by metathesis from LnI_2(THF)_2 and K(Ph_2pz) in THF, whilst the former has also been obtained by redox transmetallation from [Hg(Ph_2pz)_2] and ytterbium metal and by reaction of 3,5-diphenylpyrazole with Yb(C_6F_5)_2, and the latter from protolysis of [Sm{N(SiMe_3)_2}_2(THF)_2] with Ph_2pzH, followed in each case by crystallisation of the crude product from DME. Europium(II) 3,5-di-tert-butylpyrazolate was synthesised by a redox transmetallation/ligand exchange reaction between europium metal chunks, diphenylmercury(II), and 3,5-di-tert-butylpyrazole (tBu_2pzH) in the presence of mercury metal in THF, and [Eu(tBu_2pzH)_2(DME)_2] was isolated on crystallisation of the crude product from DME. The X-ray crystal structures of [Ln(L)_2(DME)_2] (Ln=Yb, L = bind or azin; Ln = Eu or Sm, L = Ph_2pz; Ln = Eu, L = tBu_2pz), each of a different crystallographic form, reveal eight-coordinate lanthanoid complexes with two #eta#~2-pyrazolate and two chelating DME ligands, but the structures differ in the relationship (cisoid or transoid) between the pyrazolate ligands. Thus cen-Ln-cne (cen = centre of the N-N bond) angles of 106.7 deg [Yb(bind)_2(DME)_2] (3a), 141.4 deg [Yb(azin)_2(DME)_2] (3c), 142.2 deg [Eu(Ph_2pz)_2(DME)_2] (4a), 107.4 deg [Eu(tBu_2pz)_2(DME)_2] (4b), and 102.1 deg [Sm(Ph_2pz)_2(DME)_2] (5) are observed.