So far, we have been mainly working in the field of Objective 1 (EXPANDING 0D CLUSTERS TO FUNCTIONAL (MULTI)METALLIC BUILDING BLOCKS) and Objective 2 (CONVERTING ATOM-PRECISE CLUSTERS INTO DEFINED NANO-ARCHITECTURES), with some first steps into Objective 3 (BI-BASED NANO-ARCHITECTURES AS FUNCTIONAL MATERIALS).
We have summarized recent developments in the field (Acc. Chem. Res. 2023, 56, 1018–1030).
New reactions involving the compound [K(crypt-222)]2(Sn2Bi2) have led to further understanding of the redox chemistry of this compound. Depending on the chemical oxidant added to [K(crypt-222)]2(Sn2Bi2) different larger cluster anions are obtained, either: [K(crypt-222)]2(Sn7Bi2) or [K(crypt-222)]2(Sn4Bi4) (Z. Anorg. Allg. Chem. 2024, 650, e202300229). Understanding this seemingly simple process is an essential first step for further investigations into producing functional Bi nanomaterials that will be undertaken as the project moves into the next stages. Another work that helped expand our knowledge on binary Zintl anions included the access of [(Bi7)Zn(Bi7)]4–, only the second known compound comprising the polycyclic Bi73– anion as a ligand to a metal atom (Eur. J. Inorg. Chem. 2024, 27, e202300514, highlighted by a Front Cover).
A significant milestone in the field of polybismuthides was reached. The elusive planar Bi5− was trapped in a metal complex for the first time. This anion, while it has been previously observed in mass spectrometric measurements, was isolated as part of the mixed valent inverse sandwich complex [{IMesCo}2Bi5]. A remarkable neutral compound that is reminiscent of numerous examples for the lighter group 15 elements and isovalent cyclopentadienide. The work is under review at a high-impact journal (preprint: DOI: 10.21203/rs.3.rs-4622749/v1). It demonstrates how anionic clusters can be transformed into new moieties that overall give a neutral complex rather than as part of an ionic cluster. This compound bridges the gap between anionic clusters and neutral molecular complexes, an important transformation that is a foundational step into our targets of transforming anionic clusters into neutral compounds.
In partnership with collaborators, we have expanded upon actinide-Bi clusters. Additionally, new ternary clusters containing lanthanides have been prepared in our own labs. The compound [K(crypt)]2[{(C5Me4H)2La}3Sn2Bi3] was synthesised in a reproducible and effective manner, and it displays a unique all-metal aromaticity which can be investigated spectroscopically. This achievement is an excellent way forward into understanding the unique electronic properties of polybismuthide cluster anions, and the works are also under revision at a high-impact journal. Another series of lanthanide-based clusters allowed insight into the effect of La3+ on the formation of endohedral Zintl clusters featuring indium-bismuth shells, like [La@In2Bi11](μ-Bi)2[La@In2Bi11]}6− (Inorg. Chem. 2024, 63, 9670–9675).
The anion [{CpRu}3Bi6]−, which we prepared, represents a highly intriguing molecule. Owing to its remarkably regular shape, the inner {Bi6} triangular prism displays a unique form of aromaticity that is based off an orbital resembling f-type symmetry. This phenomenon we have termed as φ-aromaticity is exclusive, so far, to bismuth, highlighting what makes this element so special. The anion has been partnered with two different counterions, either [K(crypt)]+ or [K(18-crown-6)]+, and can be prepared on a good scale which opens up the door for follow-up chemistry and further understanding into the electronic properties that polybismuthides possess (Nat. Chem. 2023, 15, 347–356, Z. Anorg. Allg. Chem. 2023, 649, e202300121).
Several {Bix} moieties are known, but interestingly we have noticed a new trend in {Bi6} systems. A commonly used transition metal fragment used are so-called 12 electron fragments (such as {CpRu}+ mentioned above) and we have recently seen that the nature of the ligand and metal centre greatly impacts the geometry of the {Bi6} and subsequently the electronic situation within the bismuth-core. For example, {CpRu}+ gives a perfectly symmetrical trigonal prism, {(cod)Ir}+ gives a distorted trigonal prism and {(hmds)Zn}+ gives an open boat-like geometry. Detailed studies combining experiments and sophisticated quantum chemistry have been undertaken; the work is currently being prepared for submission to a high-impact journal.
Our work so far as part of BiCMat has opened up the way to new polybismuthide cluster motifs and identified and studied a number of new properties and phenomena currently unique to bismuth. This foundation has built a great platform as we grow into the next stages of the project.
