W. Lamberts, H. Lueken, U. Elsenhans
Nov 3, 1986
Citations
0
Influential Citations
26
Citations
Journal
Inorganica Chimica Acta
Abstract
Abstract The crystal structures of two modifications of gadoliniumdicyclopentadienidebromide, [Gd(C5H5)2Br]2 (I) and 1∞[Gd(C5H5)2Br] (II) have been determined from X-ray diffraction data. I crystallizes in the [Sc(C5H5)2Cl]2-type structure, space group P21/c, with a=14.110(3), b=16.488(3), c= 13.765(3) A, β=93.25(2)°, V=3197(2) A3, and Dc= 2.289 g cm−3 for Z=6 molecules. II crystallizes in space group P21/c with a=5.946(7), b=8.447(5), c=20.239(9) A, β=90.11(4)°, V=1020(2) A3, Dc=2.392 g cm−3 for Z=4 formula units. The structures have been refined by full matrix least-squares techniques to conventional R factors of 0.034 for 3014 (I) and 1964 (II) reflections (with I>2σ(I)). I consists of dimers with two bromine bridges (mean GdBr 2.872 A). II has a double chain structure with alternating juxtaposition of gadolinium and bromine atoms (GdBr 2.912 A (once) and 3.133 A (twice)). The arrangement of the C5H5 groups with regard to the metal η5 fashion) is nearly identical in I and II (mean GdC 2.63(1) A (I) and 2.62(1) A (II)). Single crystals of I and II are obtained by sublimation at different temperatures. The formation of both modifications is discussed as to its dependence on the state of the gaseous phase equilibrium [Gd(C5H5)2Br]2 ⇄ 2Gd(C5H5)2Br. Obviously, I crystallizes from gaseous phase dimers while II forms from the monomers.