A mixed phosphine sulfide/selenide structure as an instructional example for how to evaluate the quality of a model

Authors

• Sean Parkin
• Jeremy Cunningham, Grand Valley State University
• Brian Rawls, Grand Valley State University
• John E. Bender, Grand Valley State University
• Richard J. Staples
• Shannon Biros, Grand Valley State UniversityFollow

Keywords

checkCIF alerts, F 2 obs vs F 2 calc, OMIT command, outliers, displacement ellipsoids, solid solution, disordered electron density, standard inter­atomic distances, crystal structure

Disciplines

Chemistry | Physical Sciences and Mathematics

Abstract

This paper compares variations on a structure model derived from an X-ray diffraction data set from a solid solution of chalcogenide derivatives of cis-1,2-bis­(di­phenyl­phosphan­yl)ethyl­ene, namely, 1,2-(ethene-1,2-di­yl)bis­(di­phenyl­phoshpine sulfide/selenide), C₂₆H₂₂P₂S_1.13Se_0.87. A sequence of processes are presented to ascertain the composition of the crystal, along with strategies for which aspects of the model to inspect to ensure a chemically and crystallographically realistic structure. Criteria include mis-matches between F _obs ² and F _calc ², plots of |F _obs| vs |F _calc|, residual electron density, checkCIF alerts, pitfalls of the OMIT command used to suppress ill-fitting data, comparative size of displacement ellipsoids, and critical inspection of inter­atomic distances. Since the structure is quite small, solves easily, and presents a number of readily expressible refinement concepts, we feel that it would make a straightforward and concise instructional piece for students learning how to determine if their model provides the best fit for the data and show students how to critically assess their structures.

Original Citation

Parkin, S., Cunningham, J., Rawls, B., Bender, J. E., Staples, R. J., & Biros, S. M. (2023). A mixed phosphine sulfide/selenide structure as an instructional example for how to evaluate the quality of a model. Acta Crystallographica Section E: Crystallographic Communications, 79(Pt 4), 246–253. https://doi.org/10.1107/S2056989023002700

ScholarWorks Citation

Parkin, Sean; Cunningham, Jeremy; Rawls, Brian; Bender, John E.; Staples, Richard J.; and Biros, Shannon, "A mixed phosphine sulfide/selenide structure as an instructional example for how to evaluate the quality of a model" (2023). Open Access Publishing Support Funded Articles. 162.
https://scholarworks.gvsu.edu/oapsf_articles/162