Try Another Crystal: Crystal-Dependent Disorder of Pentaphosphaferrocene within the Same Crystallization

The degree of disorder of [Cp '' Fe(eta(5)-P-5)] [Cp '' = eta(5)-1,3-(tBu)(2)C5H3] molecules with respect to their mirrored positions in the orthorhombic Pca2(1) space group varies from similar to 1 to 24% depending on the single crystal chosen from the same sample for the X-ray structural determination. This unusual behavior is caused by stacking faults in adjacent layers parallel to the (001) direction giving rise to two polytypes. A comprehensive search in the Cambridge Structural Database revealed only a few similar examples of the crystal-dependent disorder caused by stacking faults. Moreover, crystals of [Cp '' Fe(eta(5)-P-5)] possessing a low amount of stacking faults demonstrate slight temperature-induced superstructural ordering (modulation) between 20 and 80 K, accompanied by a doubling of the b parameter (b' -> 2 x b).

Automated summary

This study found that the degree of disorder between the mirrored positions of [Cp'' Fe(η(5)-P-5)] molecules in the orthorhombic Pca2(1) space group varies, ranging from 1% to 24% depending on the selected single crystal for X-ray structural determination. This unusual behavior is caused by stacking faults in adjacent layers, resulting in two polytypes. Additionally, crystals with fewer stacking faults demonstrate temperature-induced superstructural ordering.