Two problematic structures: partial residual electron density in a crown ether and cages with 4 metal centers and 8 disordered anions

TL;DR

The paper discusses two unresolved crystal structures involving a crown ether and a metal-containing cage, both with problematic electron density and disorder.

Contribution

The paper presents two problematic crystal structures that highlight challenges in modeling residual electron density and disorder.

Findings

A Ni complex with Cs cations and 18-Crown-6 shows residual electron density in the crown ether cavity, likely due to a water molecule with partial occupancy.

A cage with 4 metal centers and 8 disordered anions was analyzed, but the disorder could not be refined satisfactorily due to poor data quality.

The author chose not to publish the structures due to unsatisfactory refinement results.

Abstract

I will discuss two problematic structures. I have decided not to publish these structures because I am not satisfied with the refinement, but I think they are worth discussing.

The first structure is a Ni complex with Cs cations, 18-Crown-6, and residual electron density in one of the crown ether’s cavity. The residual electron density could be due to a cation or more likely a water molecule with partial occupancy, but it could not be successfully modeled.

The second structure is a large cage with 4 metal centers and 8 disordered anions. The data quality is not very good, and the anions are highly disordered. Disorder could be modeled, but the resulting structure has poor refinement parameters.