Ab Initio Structure Determination of Two Polymorphs of Cyclopentadienylrubidium in a Single Powder Pattern

Abstract

The structures of two polymorphic phases of solid RbC5H5 have been solved ab initio by high-resolution powder X-ray diffraction measured in a single powder pattern. The compound crystallizes in space group Pbcm (phase I), Z = 8, with unit-cell parameters a = 9.3396 (1), b = 10.9666 (1), c = 10.5490 (1) Å, and in space group Pnma, Z = 4 (phase II), with unit- cell parameters a = 10.7990 (2), b = 8.6923 (2), c = 5.7061 (2) Å. Both phases show polymeric zigzag chains, so-called bent-polydecker sandwich structures, with an. average Rb—Cpz (Cp-ring-centroid) distance of 2.97 Å. Phase II contains a single chain along the a axis, whereas phase I contains two similar but crystallographically independent chains perpendicular to each other along the b axis and along the c axis, leading to a more complex coordination sphere around the Rb atoms. The chains are bent with Cpz—Rb—Cpz angles ranging from 123.5 to 136.5°.

Solid-State Structures of Base-Free Rubidium and Cesium Pentamethylcyclopentadienides. Determination by High-Resolution Powder Diffraction

“…The solid-state structures of 2 and 3 are comparable to those of the polymeric zigzag chains found in KCp, 2 -RbCp, 3 and CsCp 4 (RbCp crystallizes in two different phases). 3 Selected data are given in Table 1.…”

“…In RbCp*, compared to -RbCp, the Rb-Rb′ distance is about 0.1 Å longer while the Rb′-Rb-Rb′′ angle is the same (Rb-Rb′ distance in 2 6.033(4) Å and in -RbCp 5.926(4) Å; Rb′-Rb-Rb′′ angle in 2 131.0(1)°and in -RbCp 131. 3(1)°). For the cesium Cp/Cp* compounds a different situation for the Cs-Cs′ distance was found.…”

“…3 Selected data are given in Table 1. In RbCp*, compared to -RbCp, the Rb-Rb′ distance is about 0.1 Å longer while the Rb′-Rb-Rb′′ angle is the same (Rb-Rb′ distance in 2 6.033(4) Å and in -RbCp 5.926(4) Å; Rb′-Rb-Rb′′ angle in 2 131.0(1)°and in -RbCp 131.…”

Crystal structure of copper(ii) citrate monohydrate solved from a mixture powder X-ray diffraction pattern

“…Moreover, materials are sometimes obtained not as a pure phase but in a mixture with other known or unknown phases (Halasz and Dinnebier, 2010). different peak widths (Dinnebier et al, 1997). This is particularly difficult if the peaks belonging to different phases cannot be distinguished on the grounds of e.g.…”

Polymorphism of a nickel polymerization catalyst

“…But it is almost impossible to decide which of the predicted crystal structures will be formed during an experiment and what procedure leads to one particular polymorphic form [15]. In contrast to organic or inorganic substances much less attention had been paid to the polymorphism of organometallic compounds [16][17][18][19] although for certain compounds more than 10 different forms are known [20]. Organometallic compounds are involved as catalysts, precatalysts or intermediates in many homogeneous and heterogeneous processes.…”