|
terryewnert
| Založen: 09. 04. 2025 |
| Příspěvky: 11 |
|
|
|
| Zaslal: 25.4.2025 22:52 |
|
|
 |
|
The involvement of the 4f orbitals of lanthanide metals in chemical reactions is almost as rare as their natural abundance on Earth. However, a recent study has observed the 4f orbital of cerium actively participating in bond formation, initiating a unique chemical reaction.
Researchers discovered that a cerium-containing cyclic complex exhibited a 4f-covalent interaction, which led to a ring-opening isomerization from cyclopropene to allene. These findings were reported in Nature Chemistry.
Lanthanides, heavy rare-earth elements spanning positions 57 to 71 on the periodic table, play crucial roles in modern technologies, from electronics to clean energy solutions. In nature, these elements are often found mixed in ores, and separating them is both complex and energy-intensive. Gaining a deeper understanding of how lanthanides bond with other atoms at an electronic level could eventually help develop more efficient separation techniques.
Historically, the 4f orbitals of lanthanides have been known to be largely inert in chemical reactions. Shielded by the outer 5s and 5p orbitals and located close to the atomic nucleus, 4f orbitals typically do not overlap easily with other atomic orbitals, making their participation in bonding rare.
Recent work has shown that 4f and 5f orbitals can be involved in coordination chemistry, where metal atoms bond with ligands—ions or molecules donating electron pairs to metals. However, direct evidence linking 4f-orbital covalency to chemical reactivity has remained elusive.
To explore this, the research team synthesized a set of tetravalent metal (M4+)–cyclopropenyl complexes, where the metal (M) was titanium (Ti), zirconium (Zr), cerium (Ce), hafnium (Hf), or thorium (Th). Each complex included a cyclopropene-based ligand framework and three nitroxide ligands forming a structured environment around the metal center.
https://www.kumander.org/viewtopic.php?t=319
https://www.kumander.org/viewtopic.php?t=320
https://www.kumander.org/viewtopic.php?t=321
https://www.kumander.org/viewtopic.php?t=322
https://www.kumander.org/viewtopic.php?t=323
https://www.kumander.org/viewtopic.php?t=324
https://www.kumander.org/viewtopic.php?t=325
https://www.kumander.org/viewtopic.php?t=326
https://www.kumander.org/viewtopic.php?t=327
https://www.kumander.org/viewtopic.php?t=328
https://www.kumander.org/viewtopic.php?t=329
https://www.kumander.org/viewtopic.php?t=330
https://www.kumander.org/viewtopic.php?t=331
https://www.kumander.org/viewtopic.php?t=332
https://www.kumander.org/viewtopic.php?t=333
https://www.kumander.org/viewtopic.php?t=334
https://www.kumander.org/viewtopic.php?t=335
https://www.kumander.org/viewtopic.php?t=336
https://www.kumander.org/viewtopic.php?t=337
https://www.kumander.org/viewtopic.php?t=338
https://www.kumander.org/viewtopic.php?t=339
https://www.kumander.org/viewtopic.php?t=340
https://www.kumander.org/viewtopic.php?t=341
https://www.kumander.org/viewtopic.php?t=342
https://www.kumander.org/viewtopic.php?t=343
https://www.kumander.org/viewtopic.php?t=344
https://www.kumander.org/viewtopic.php?t=345
https://www.kumander.org/viewtopic.php?t=346
https://www.kumander.org/viewtopic.php?t=347
https://www.kumander.org/viewtopic.php?t=348
https://www.kumander.org/viewtopic.php?t=349
https://www.kumander.org/viewtopic.php?t=350
https://www.kumander.org/viewtopic.php?t=351
https://www.kumander.org/viewtopic.php?t=352
https://www.kumander.org/viewtopic.php?t=353
https://www.kumander.org/viewtopic.php?t=354
https://www.kumander.org/viewtopic.php?t=355
https://www.kumander.org/viewtopic.php?t=356
https://www.kumander.org/viewtopic.php?t=357
https://www.kumander.org/viewtopic.php?t=358
https://www.kumander.org/viewtopic.php?t=359
https://www.kumander.org/viewtopic.php?t=360
https://www.kumander.org/viewtopic.php?t=361
https://www.kumander.org/viewtopic.php?t=362
https://www.kumander.org/viewtopic.php?t=363
https://www.kumander.org/viewtopic.php?t=364
https://www.kumander.org/viewtopic.php?t=365
https://www.kumander.org/viewtopic.php?t=366
https://www.kumander.org/viewtopic.php?t=367
https://www.kumander.org/viewtopic.php?t=368
https://www.kumander.org/viewtopic.php?t=369
https://www.kumander.org/viewtopic.php?t=370
https://www.kumander.org/viewtopic.php?t=371
https://www.kumander.org/viewtopic.php?t=372
https://www.kumander.org/viewtopic.php?t=373
https://www.kumander.org/viewtopic.php?t=374
https://www.kumander.org/viewtopic.php?t=375
https://www.kumander.org/viewtopic.php?t=376
https://www.kumander.org/viewtopic.php?t=377
https://www.kumander.org/viewtopic.php?t=378
https://www.kumander.org/viewtopic.php?t=379
https://www.kumander.org/viewtopic.php?t=380
https://www.kumander.org/viewtopic.php?t=381
https://www.kumander.org/viewtopic.php?t=382
https://www.kumander.org/viewtopic.php?t=383
https://www.kumander.org/viewtopic.php?t=384
https://www.kumander.org/viewtopic.php?t=385
https://www.kumander.org/viewtopic.php?t=386
https://www.kumander.org/viewtopic.php?t=387
https://www.kumander.org/viewtopic.php?t=388
https://www.kumander.org/viewtopic.php?t=389
https://www.kumander.org/viewtopic.php?t=390
https://www.kumander.org/viewtopic.php?t=391
https://www.kumander.org/viewtopic.php?t=392
https://www.kumander.org/viewtopic.php?t=393
https://www.kumander.org/viewtopic.php?t=394
https://www.kumander.org/viewtopic.php?t=395
https://www.kumander.org/viewtopic.php?t=396
https://www.kumander.org/viewtopic.php?t=397
https://www.kumander.org/viewtopic.php?t=398
Among these, only the cerium (Ce4+) complex underwent a single-crystal-to-single-crystal isomerization, transforming into a cerium–allenyl complex.
Using single-crystal X-ray diffraction, the team captured the transformation process, where the cerium complex changed its structure without altering its chemical composition. The experimental observations, backed by theoretical calculations, suggest that cerium’s 4f orbital plays a crucial role in bonding with the reactive intermediate and stabilizing it to promote the ring-opening event.
This comparative analysis of the chemical behavior among structurally and electronically similar d- and f-block metal complexes reveals that 4f-orbital covalency can indeed drive distinct chemical reactivity. The researchers believe these findings could pave the way for further studies on orbital covalency in molecular compounds, particularly those involving solid-state chemical transformations.
|
|
