Octaisopropylmetallocenes of the lanthanoids Sm(1-Sm), Eu (1-Eu), and Yb (1-Yb) can be obtained easily from the diiodides of the rare earth elements. Like the hexa-(tert.-butyl)metallocenes 2-Sm, 2-Eu, and 2-Yb, they show no tendency towards coordination of donor solvent molecules or alkali salts. The decaisopropylmetallocenes 3-Sm, 3-Eu und 3-Yb have been synthesized from the metal and the free pentaisopropylcyclopentadienyl radical. The three europocenes 1-Eu, 2-Eu, and 3-Eu show fluorescence in day-light or under UV irradiation (336 nm). Crystalline 1-Eu and 2-Eu are bent sandwich complexes, whereas for the decaisopropyl derivative 3-Eu axial symmetry with parallel fivemembered rings has been observed.
COMMUNICATIONS materials causes the condensation of the silicate layers, giving the zeolite structures MCM-22 and ferrierite. Similar behavior can also be expected for RUB-15, since the silicate layer terminated with silanol groups should be the perfect subunit for the formation of the silica framework of the zeolite sodalite.
Experimental ProcedureRUB-15 crystallized from a reaction mixture with the following composition: SiO,:TMAOH:H,O = 1.00:0.75:55.52 The solution was filled in Teflon-lined autoclaves (60% filling factor) and kept in an oven at a temperature between 120 and 140 C for about four weeks. The reaction product was filtered, washed with distilled water. dried at 80 c. and subsequently identified by X-ray powder diffraction.
The largest interplanar distance known to date between adjacent parallel rings of any sandwich compound (5.497(3) Å) is displayed by decaisopropylbarocene, the first heavy alkaline earth metal sandwich compound to possess axial symmetry. A new efficient metallocene formation [Eq. (1)] utilizes the free cyclopentadienyl radical [C R ] (R=CHMe ) as an oxidizing agent for elemental Ca, Sr, and Ba (M).
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