Organoamido- and Aryloxo-Lanthanoids. V. Preparations of Low-Coordinate Lanthanoid(II) Phenolates, Ln (OC6H2But2-2,6-X-4)2( thf )n (Ln = Yb or Eu; X = H, Me or BuT; N = 2 or 3) and the X-Ray Crystal Structure of Five-Coordinate [Yb (OC6H2But2-2,6-X-4)2( thf )3].thf

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Abstract
Lanthanoid (II) complexes of bulky aryl oxides, Ln (OC6H2But2-2,6-X-4)2 ( Ln = Yb or Eu ; X = H, Me or But) 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 (OC6H2But2-2,6-X-4)2(thf)3 complexes. Crystallization of Yb (OC6H2But2-2,6-X-4)2( thf )3 (X = H or Me) from toluene yields Yb (OC6H2But2-2,6-X-4)2( thf )2. The X-ray crystal structure of [ Yb (OC6H2But3-2,4,6)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 (OC6H2But2-2,6-Me-4)2(thf)n showing four coordination (n = 2) and five coordination (n = 3), given in a preliminary communication,1 are further discussed.

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