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Hydride and Seek: Comparing Crystallographic Hydride Placement Techniques with an Open-Shell Cobalt Complex
Ryan S Donnelly1, Theodore J Gerard1, Sebastian M Krajewski1
1Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States.
ACS Central Science
|July 25, 2026
Summary
Electron diffraction accurately locates hydrides in organometallic chemistry, outperforming X-ray diffraction and quantum crystallography. This method, especially with dynamical refinement, provides precise metal-hydride distances, matching neutron diffraction benchmarks.
Area of Science:
- Organometallic Chemistry
- Crystallography
- Materials Science
Background:
- Accurate hydride localization is essential in organometallic chemistry.
- X-ray diffraction (XRD) has limitations in precisely locating hydrides.
- Electron diffraction (ED) and quantum crystallography (QC) are potential alternatives.
Purpose of the Study:
- To systematically compare XRD, QC (Hirshfeld atom refinement - HAR), density functional theory (DFT), and electron diffraction (3D-ED/MicroED) for hydride localization.
- To evaluate the precision of these methods against a neutron diffraction reference structure.
- To define optimal conditions for 3D-ED/MicroED in determining metal-hydride distances.
Main Methods:
- Single-crystal neutron diffraction as the reference method.
- Single-crystal X-ray diffraction with and without HAR (NoSpherA2).
- Density functional theory (DFT) calculations.
- 3D-ED/MicroED refined using kinematical and dynamical formalisms.
Main Results:
- Conventional XRD shows lower precision than neutron diffraction.
- HAR exhibits systematic deviations from the neutron diffraction benchmark.
- DFT results are closer to neutron diffraction values than HAR.
- 3D-ED/MicroED with dynamical refinement accurately localizes the hydride and agrees well with neutron data.
- Dynamical refinement is critical for hydride peak assignment in ED.
Conclusions:
- 3D-ED/MicroED, particularly with dynamical refinement, is a powerful technique for precise metal-hydride distance determination.
- Electron diffraction overcomes limitations of XRD and HAR for hydride localization.
- This study establishes conditions for high-precision hydride analysis using 3D-ED/MicroED.
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