Organoamido- and Aryloxo-Lanthanoids. V. Preparations of Low-Coordinate Lanthanoid(II) Phenolates, Ln (OC₆H₂Bu^t₂-2,6-X-4)₂( thf )_n (Ln = Yb or Eu; X = H, Me or Bu^T; N = 2 or 3) and the X-Ray Crystal Structure of Five-Coordinate [Yb (OC₆H₂Bu^t₂-2,6-X-4)₂( thf )₃].thf

Abstract

Lanthanoid (II) complexes of bulky aryl oxides, Ln (OC₆H2Bu^t₂-2,6-X-4)₂ ( Ln = Yb or Eu ; X = H, Me or Bu^t) have been prepared by one or more of the following methods: ( i ) reaction of Ln (C₆F₅)₂ with the appropriate phenol, (ii) reaction of the lanthanoid metal, Hg(C₆F₅)₂ and the phenol, and (iii) reaction of the lanthanoid metal with the corresponding thallium(I) phenolate, in tetrahydrofuran ( thf ), and they have been isolated as Ln (OC₆H₂Bu^t₂-2,6-X-4)₂(thf)₃ complexes. Crystallization of Yb (OC₆H₂Bu^t₂-2,6-X-4)₂( thf )₃ (X = H or Me) from toluene yields Yb (OC₆H₂Bu^t₂-2,6-X-4)₂( thf )₂. The X-ray crystal structure of [ Yb (OC₆H₂Bu^t_3-2,4,6)₂( thf )₃]. thf [monoclinic, a 10.20(1), b 32.97(2), c 16.018(4) Ǻ, β 93.52(8)°, V 5375 Ǻ³, Z 4, 2734 'observed' data refined to R 0.070] shows distorted square pyramidal five coordination for ytterbium with an apical thf oxygen [ Yb -O 2.44(1)Ǻ], and transoid phenolate oxygens [ Yb -O 2.21(1), 2.22(1)Ǻ, O- Yb -O 149.0(6)°] and trans thf oxygens [ Yb -O 2.47(2), 2.48(1)Ǻ, O-Yb -O 177.3(5)°] in the square plane. Four methyl groups ( Yb…C 3.89-4.15 Ǻ) across the square plane away from the apical oxygen may block coordination of an additional ligand. X-Ray structures of Yb (OC₆H₂Bu^t₂-2,6-Me-4)₂(thf)n showing four coordination (n = 2) and five coordination (n = 3), given in a preliminary communication,¹ are further discussed.