Refined occupancies of the predominantly Ni site in complexes 1, 2, and 3 using the various methods indicated (AXD = anomalous [or resonant] x-ray diffraction). From C.E. Casaday et al., Inorg. Chem. 64 (6), 3090-3100 (2025). Copyright © 2025 American Chemical Society Society
Mixed-metal clusters are composed of at least three metal atoms bonded together through metal-metal bonds. The metals can be the same or different, leading to diverse structures and properties.
These clusters exhibit a wide range of structures, from simple triangular or linear arrangements to more complex polyhedra. The structure can be influenced by the types of metals involved, the ligands present, and the reaction conditions.
These clusters can be synthesized through various reactions, including pyrolysis and the reaction of carbonylmetalates. They are often characterized by unique structures and properties, and are of great importance in small-molecule activation and catalysis. Their ability to exhibit unique catalytic activity and serve as precursors for nanoparticles make them valuable in various fields including catalysis and small-molecule activation for materials science. For example, both biological nitrogen fixation and photosynthetic splitting of water into oxygen are thought to involve multimetallic catalytic sites with d-block transition metals.
A team of researchers employed research techniques, primarily synchrotron-produced x-ray diffraction (XRD), to determine the effect of integrated resolution, data scaling, structural refinement, and crystal symmetry on the extracted scattering perturbations and their uncertainties for anomalous (resonant) x-ray diffraction on mixed-metal molecular clusters.
The XRD studies were carried out at the NSF’s ChemMatCARS Advanced Crystallography facility at beamline 15-ID of the Argonne Advanced Photon Source, beamline 12.2.1 at the Advanced Light Source at the Lawrence Berkeley National Laboratory, and a home source. The team also employed energy-dispersive spectra for data confirmation.
Their studies encompassed probes of the metal constituency, substitutional homogeneity, and positional disorder of both biased and unbiased ligand environments.
Results of this study reveal highly ordered structural compositions, even when statistical mixing was anticipated. The team found that anomalous x-ray diffraction studies are indispensable for assigning metal-site occupancies within heterobimetallic clusters. Overall, these results provide multiple strategies for investigating the metal site occupancies of heterobimetallic clusters.
See: Claire E. Casaday1, Cristin E. Juda1, Shao-Liang Zheng1, Simon J. Teat2, Tieyan Chang3, Yu-Sheng Chen3, and Theodore A. Betley1*, “Occupancy Determination from Resonant X-ray Diffraction,” Inorg. Chem. 64 (6), 3090-3100 (2025). DOI: 10.1021/acs.inorgchem.4c05423.
Author affiliations: 1Harvard University, 2Lawerence Berkley National Laboratory, 3The University of Chicago
Correspondence: *betley@chemistry.harvard.edu
C.E.C. and C.E.J. thank the National Science Foundation (NSF) for Predoctoral Fellowships. This work was supported by grants from the National Institutes of Health (NIH) (GM-098395), NIH (GM-145752), the U.S. Department of Energy (DOE) (DE-SC0008313), NSF (CHE-2247817), and Harvard University. The authors thank the X-ray Core facility at Harvard University, of the Major Research Instrumentation (MRI) Program of the NSF (NSF-2216066). The SEM-EDS analysis was performed at the Harvard University Center for Nanoscale Systems (CNS), a member of the National Nanotechnology Coordinated Infrastructure Network (NNCI), which is supported by the NSF(ECCS-2025158). Crystallographic data for 1 and 3 were obtained at ChemMatCARS Sector 15 at the Advanced Photon Source (APS). The APS is a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE- AC02-06CH11357. NSF’s ChemMatCARS is supported by the NSF under grant number NSF/ CHE-1834750. The Advanced Light Source is a DOE Office of Science User Facility operated under contract no. DE-AC02- 05CH11231.
For information on the NSF’s ChemMatCARS Advanced Crystallography program, contact:
Yu-Sheng Chen
(630) 252-0471
yushengchen@uchicago.edu