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tris(trimethylsily1)cyclopentadienon (lo), Bromierung von (9) bei 0 "C und HBr-Eliminierung das stellungsisomere Bromdienon ( I I).

Abstract Bicyclic acyloxyfluoroboranes 3 react with BF3 by an insertion reaction to form bicyclic diacyloxy- pentafluoro-μ3-oxotriboranes of the 2.2.6.10.10-pentafluoro-4.8-dialkyl-1.3.5.7.9-pentaoxa- 2.6.10-tribora-bicyclo(4.4.0)decadiene type 4. A X-ray crystal structure determination of 4b is reported. NM R data of 4b in the solid state and in solution are discussed.

Abstract Cs6Ga2Se6 can be prepared from mixtures of Cs2Se and Ga2Se3. The transparent single crystals of the moisture sensitive compound (m.p. 685 °C) crystallize in the monoclinic system with a = 848.0(5), b = 1364.4(5), c = 1111.5(5) pm, β = 126.22(5)° (T = -150 °C, Z = 2, space group P21/c). The gallium atoms pairwisely occupy selected tetrahedral holes between layers formed by the cesium and selenium ions. This structural principle leads to the formation of double tetrahedral isolated [Ga2Se6] 6- ions.

Abstract Acyloxyfluoroboranes Trimeric alkoxydifluoroboranes (F2BOR)3 (2) react with organic acid anhydrides by substitution of a ring group OR forming monocyclic acyloxyfluoroboranes of the type 2,2,6,6-tetrafluoro-l,4-dialkyl-l,3,5-trioxa-2,6-diboracyclohexene (3). The X-ray crystal structure determination of 3a shows two conformational isomers: two planar and two non-planar six-membered rings are present in the unit cell. The ring conformation is influenced by weak intermolecular H — F interactions.