Closo Research Articles

π-Complexes Derived from Non-classical Diboriranes: Side-on vs. End-on Carbonylative Ring Expansion.

Unlike cyclopropanes, the analogous B2C species, the diboriranes, tend to adopt non-classical Hückel-aromatic structures with bridging moieties R between the boron atoms. The coordination of the thus generated cyclic 2e- π-system to transition metals is completely unexplored. We here report that complexation of non-classical diboriranes cyclo-μ-RB2Dur2CPh (R = H, SnMe3; Dur = 2,3,5,6-tetramethylphenyl) to Fe(CO)3 fragments allows for the carbonylative ring expansion of the B2C ring to either four- or five-membered rings depending on the nature of the BRB 3-center-2-electron bond (3c2e): the H-bridged diborirane (R = H) initially reacts with Fe2(CO)9 to the allylic π-complex with an agostic BH/Fe interaction. Subsequent formal hydroboration of CO from excess Fe2(CO)9 results in the side-on ring expansion to a five-membered B2C2O ring, coordinated to the Fe(CO)3 moiety. In contrast, in case of the stannyl-bridged diborirane (R = SnMe3) under the same conditions, CO is added end-on to the B-B bond with the carbon terminus formally inserting into the B2Sn 3c2e-bond. The two carbonylative ring expansion products can also be described as nido and closo clusters, respectively, according to the Wade-Mingos rules.

π‐Complexes Derived from Non‐classical Diboriranes: Side‐on vs. End‐on Carbonylative Ring Expansion

Unlike cyclopropanes, the analogous B2C species, the diboriranes, tend to adopt non‐classical Hückel‐aromatic structures with bridging moieties R between the boron atoms. The coordination of the thus generated cyclic 2e− π‐system to transition metals is completely unexplored. We here report that complexation of non‐classical diboriranes cyclo‐μ‐RB2Dur2CPh (R = H, SnMe3; Dur = 2,3,5,6‐tetramethylphenyl) to Fe(CO)3 fragments allows for the carbonylative ring expansion of the B2C ring to either four‐ or five‐membered rings depending on the nature of the BRB 3‐center‐2‐electron bond (3c2e): the H‐bridged diborirane (R = H) initially reacts with Fe2(CO)9 to the allylic π‐complex with an agostic BH/Fe interaction. Subsequent formal hydroboration of CO from excess Fe2(CO)9 results in the side‐on ring expansion to a five‐membered B2C2O ring, coordinated to the Fe(CO)3 moiety. In contrast, in case of the stannyl‐bridged diborirane (R = SnMe3) under the same conditions, CO is added end‐on to the B‐B bond with the carbon terminus formally inserting into the B2Sn 3c2e‐bond. The two carbonylative ring expansion products can also be described as nido and closo clusters, respectively, according to the Wade‐Mingos rules.

Benzvalene-like Carboranes: Genuine Rule Breakers and Good Kinetic Stability.

Substituents are widespread in chemistry, but it has remained quite difficult to reliably determine the thermodynamic and kinetic stabilities of substituted compounds, though they are key to helping establish a structural rule and synthetic viability, respectively. As an important class of valence isomers in the benzene family, benzvalene-like structures have been extensively studied in systems associated with electron-neutral (i.e., C, Si, Ge, Pb, and Sn) and electron-rich (e.g., P) skeletons. However, stable benzvalene-like examples associated with electron-deficient skeletons have been very limited, possibly due to the very complicated bonding patterns of electron-deficient elements. Here, we performed an extensive structural search at the density functional theory (DFT) and CBS-QB3 level for the well-known six-vertex dicarboranes (C2B4R6), one of the central families of boranes and carboranes chemistry. We unexpectedly found that all of the previously reported benzvalene-like structures III (C2B4R6) as the long-chased "rule breaker" examples of the Wade-Mingos rule (W-M rule) are not the lowest-lying structures. Promisingly, for the first time, we succeeded in identifying several substituted III as the genuine lowest-lying structures and thus true "rule breakers." Thus, "benzvalenes" present hitherto the fourth member of the lowest-lying structural patterns for the family of six-vertex dicarboranes. Moreover, the presently revealed good kinetic stability of III' (C2B4R2R'4) over a wide range of substituents promoted us to recommend a novel kind of synthesizable carboranes beyond the Wade-Mingos rule, i.e., "benzvalene-like carboranes" with all of the classical skeletal atoms.

The potential energy surface and superatomic properties of the octahedral PtSn5 cluster

Zintl (group IV elements) clusters with a special number of valence electrons often exhibit extraordinary structures and chemical bonding patterns, and the stability of them is rationalised by the Wade-Mingos rule. However, this rule is still limited for some Zintl clusters. Here, we find that the potential energy surface of PtSn5 has a single deep funnel, which leads down to the octahedron of the global minimum. The AIMD simulations demonstrate that the octahedral PtSn5 still has a good thermal stability at 1000 K. The molecular orbitals and AdNDP analyses reveal that the 20 valence electrons from five Sn atoms of the PtSn5 fill superatomic shells resulting in an electronic configuration of 1S21P61D102S2, and the electronic structure of the Pt atom is d10, well following the magic number of the Jellium model. The result is further confirmed by the density of states and the localised orbital locator. After the CO molecule is adsorbed on the PtSn5, it prefers to be located at the Pt atom. Due to the charge-transfer effect, the C–O bond length and stretching frequency appear to change significantly. Our work opens up the study on the Jellium model for Zintl clusters.

Exploring the potential energy surface of B4H42-: an exception of the Wade-Mingos rules.

An analysis of the potential energy surface of B4H42- which, according to Wade-Mingos rules should have a tetrahedral structure, is presented. Our results indicate that the global minimum has a planar diamond-like boron skeleton and that the nearest local minimum lies 7.8 kcal mol-1 above it. This isomer corresponds to a Jahn-Teller distorted tetrahedral B4H4 structure as a result of the gain of two electrons. Furthermore, the analysis of the bonding pattern using the Adaptive Natural Density Partitioning method indicates a double σ and π delocalization providing high stability. These results show that B4H42- is an exception to the Wade-Mingos rules and open the door to future experimental characterization of this compound.

Multi-phosphine-chelated iron-carbide clusters via redox-promoted ligand exchange on an inert hexa-iron-carbide carbonyl cluster, [Fe6(μ6-C)(μ2-CO)4(CO)12]2.

We report the reactivity, structures and spectroscopic characterization of reactions of phosphine-based ligands (mono-, di- and tri-dentate) with iron-carbide carbonyl clusters. Historically, the archetype of this cluster class, namely [Fe6(μ6-C)(μ2-CO)4(CO)12]2-, can be prepared on a gram-scale but is resistant to simple ligand substitution reactions. This limitation has precluded the relevance of iron-carbide clusters relating to organometallics, catalysis and the nitrogenase active site cluster. Herein, we aimed to derive a simple and reliable method to accomplish CO → L (where L = phosphine or other general ligands) substitution reactions without harsh reagents or multi-step synthetic strategies. Ultimately, our goal was ligand-based chelation of an Fe n (μ n -C) core to achieve more synthetic control over multi-iron-carbide motifs relevant to the nitrogenase active site. We report that the key intermediate is the PSEPT-non-conforming cluster [Fe6(μ6-C)(CO)16] (2: 84 electrons), which can be generated in situ by the outer-sphere oxidation of [Fe6(μ6-C)(CO)16]2- (1: closo, 86 electrons) with 2 equiv. of [Fc]PF6. The reaction of 2 with excess PPh3 generates a singly substituted neutral cluster [Fe5(μ5-C)(CO)14PPh3] (4), similar to the reported reactivity of the substitutionally active cluster [Fe5(μ5-C)(CO)15] with monodentate phosphines (Cooke & Mays, 1990). In contrast, the reaction of 2 with flexible, bidentate phosphines (DPPE and DPPP) generates a wide range of unisolable products. However, the rigid bidentate phosphine bis(diphenylphosphino)benzene (bdpb) disproportionates the cluster into non-ligated Fe3-carbide anions paired with a bdpb-supported Fe(ii) cation, which co-crystallize in [Fe3(μ3-CH)(μ3-CO)(CO)9]2[Fe(MeCN)2(bdpb)2] (6). A successful reaction of 2 with the tripodal ligand Triphos generates the first multi-iron-chelated, authentic carbide cluster of the formula [Fe4(μ4-C)(κ3-Triphos)(CO)10] (9). DFT analysis of the key (oxidized) intermediate 2 suggests that its (μ6-C)Fe6 framework remains fully intact but is distorted into an axially compressed, 'ruffled' octahedron distinct from the parent closo cluster 1. Oxidation of the cluster in non-coordinating solvent allows for the isolation and crystallization of the CO-saturated, intact closo-analogue [Fe6(μ6-C)(CO)17] (3), indicating that the intact (μ6-C)Fe6 motif is retained during initial oxidation with [Fc]PF6. Overall, we demonstrate that redox modulation beneficially 'bends' Wade-Mingo's rules via the generation of electron-starved (non-PSEPT) intermediates, which are the key intermediates in promoting facile CO → L substitution reactions in iron-carbide-carbonyl clusters.

Rule breaker boron clusters: a new class of hypoelectronic osmaborane clusters [(Cp*Os)2BnHn] (n = 6-10).

Since the pioneering electron counting rule for borane clusters was proposed by Wade, the structures and bonding of boron clusters and their derivatives have been elegantly rationalised. However, this rule and its modified versions faced problems explaining the electronic structures of less spherical deltahedra, unlike the core geometries of borate dianions [BnHn]2- (n = 6-12). Herein, we report the isolation of a series of osmaborane clusters [(Cp*Os)2BnHn], 1-5, (n = 6-10) by the thermolysis of an in situ generated intermediate, obtained from the rapid condensation of [Cp*OsBr2]2 and [LiBH4·THF], with [BH3·THF] or [BH3·SMe2]. Interestingly, all these clusters show unusual less spherical deltahedral shapes that can be generated from canonical [BnHn]2- (n = 8-12) shapes by doing diamond-square-diamond (DSD) rearrangements. The DSD rearrangements led to the generation of higher degree vertices, which are occupied by Os atoms and also generated Os-Os bonds in these clusters. Theoretical calculations revealed that these Cp*Os⋯OsCp* interactions in clusters 1-5 played a crucial role in their structural shape and electron count. These less spherical deltahedral clusters are rare, and most significantly, clusters 1-5 with (n-1) skeleton electron pairs (SEPs) do not follow Wade-Mingos electron counting rules and can be classified as hypoelectronic closo clusters.

Catalytic Potential of [B12X11]2- (X = F, Cl, Br, I, CN) Dianions.

Dodecaborate anions ([B12H12]2-) and their derivatives where hydrogen atoms are replaced by halogen, pseudohalogen, or superhalogen moieties belong to a class of very stable species, even in the gas phase. Their stability is attributed to Wade's electron counting rule that requires n + 1 pairs of skeletal electrons, n being the number of boron atoms. Consequently, [B12X11]2- (X = H, F, Cl, Br, I, CN) dianions that carry one more electron than needed to satisfy Wade's rule should not be stable, assuming that the rule applies to fragments as well. While this is the case for X = H, we show that [B12X11]2- (X = F, Cl, Br, I, CN) dianions are stable with the second electron in [B12(CN)11]2- bound by as much as 3.17 eV. More importantly, the stability of these dianions is found to have a significant effect on the activation of gas molecules such as CO2 and N2, providing a path toward the development of new catalysts.

Carbonylmetallates as Versatile 2-, 4- or 6-Electron Donor Metalloligands in Transition-Metal Complexes and Clusters: A Global Approach.

Carbonylmetallates [m]- , such as [MoCp(CO)3 ]- , [Mn(CO)5 ]- , [Co(CO)4 ]- , have long been successfully used in the preparation of hundreds of metal-metal bonded carbonyl complexes and clusters, in particular of the heterometallic type. We focus here on situations where [m]- can be viewed as a terminal, doubly or even triply bridging metalloligand, developing metal-metal interactions with one, two or three metal centers M, respectively. With metals M from the Groups 10-12, it is not straightforward or even impossible to rationalize the structure of the resulting clusters by applying the well-known Wade-Mingos rules. A very simple but global approach is presented to rationalize structures not obeying usual electron-counting rules by considering the anionic building blocks [m]- as metalloligands behaving formally as potential 2-, 4- or 6-electron donors, similarly to what is typically encountered with for example halido ligands. Qualitative and theoretical arguments by using DFT calculations highlight similarities between seemingly unrelated metal complexes and clusters and also entail a predicting power with high synthetic potential.

Exploration of the potential energy surface in mixed Zintl clusters applying an automatic Johnson polyhedra generator: the case of arachno E6M24- (E = Si, Ge, Sn; M = Sb, Bi).

A new algorithm called Automatic Johnson Cluster Generator (AJCG) is presented, which, as its name indicates, allows the definition of the desired Johnson polyhedron to subsequently carry out all the possible permutations between the atoms that form this polyhedron. This new algorithm allows the exhaustive study of the structures' potential energy surface (PES). In addition, the AJCG algorithm is helpful for the study of three-dimensional compounds such as boranes or Zintl clusters and their structural derivatives with two or more different atoms. The automatic filling of vertices is particularly useful in mixed compounds because of the possibility of taking into account all possible configurations in the structure. As a test system, we investigated the arachno-type E6M24- (E = Si, Ge, Sn; M = Sb, Bi) structure which has eight vertices and complies with Wade-Mingos rules. Initially, we defined a bipyramidal structure (10 vertices), and filled the vertices with the atoms in all possible configurations. Since the selected system has eight atoms, the two remaining vertices were filled with pseudo atoms to complete the structure. After re-optimizing the initial population generated with AJCG, a large number of isomers with energy below 10 kcal mol-1 are identified. These results show that the most stable isomers possess homonuclear M-M bonds, except Sn6Bi24-. Although the overall putative minima differ at the PBE0-D3 and DLPNO-CCSD(T) levels, they are always competitive minima. In addition to using high-precision methodologies to correctly study relative energies, applying solvent effects in highly charged systems becomes mandatory. The aromatic character of these studied systems was demonstrated qualitatively with two- and three-dimensional mapping and quantitatively by calculating the value of the z-component of the induced magnetic field at the cage center, including scalar and spin-orbit correction for relativistic effects. The compounds studied have a high degree of aromaticity, which allows us to establish that despite structural modifications (i.e., from closo to arachno), the aromaticity is preserved.

Kenneth Wade. 13 October 1932—16 March 2014

Much of Ken Wade's scientific career was devoted to developing and exploiting the chemistries of boron, aluminium, gallium and indium (the Group 13 elements). He made significant contributions to both experimental and theoretical aspects of the subject and was a highly regarded teacher and attentive research supervisor. Ken was a modest and self-critical man who had a rare ability to recognize patterns in large chemical and molecular structure data sets and express the resulting generalizations in the form of simple rules that experimental chemists could appreciate and use to predict new compounds. Ken was fascinated by the structures of cluster compounds that are based on regular polyhedral shapes. Cluster molecules generally contain groups of metal atoms linked by metal–metal bonds and located on one or more spherical shells. Since the 1960s they have attracted the attention of both academic and industrial chemists. Understanding and predicting their three-dimensional shapes raised a significant intellectual challenge for chemists. The clusters also attracted attention because they occupy an intermediate position between co-ordination compounds based on a single metal atom and the parent metal, which has an infinite number of linked metal atoms. This provided chemists with a unique opportunity to explore the evolution of their electronic and chemical properties as the cluster size increases. Ken was the first to recognize the electronic relationships connecting closo- , nido- , arachno- and hypho - clusters. These clusters are inter-related by the successive removal of vertices from a regular closo- deltahedron, i.e. a polyhedron with all the faces triangular. His ability to connect the structures of these molecules to the number of valence electrons involved in skeletal bonding represented a significant contribution to chemical bonding theories. Ken communicated his conclusions in very clearly written papers and books. This made the complexities of cluster chemistry amenable to many and especially those who did not have a strong background in quantum chemistry. The skeletal electron counting rules, or Wade's Rules, which Ken pioneered, are now very much part of the fabric of modern cluster chemistry and form an important component of modern undergraduate inorganic chemistry courses. Wade's Rules may be applied to main group and transition metal carbonyl clusters as well as clusters containing both main group and transition metal fragments. Besides providing an accessible entry into cluster chemistry for students, the rules have been used creatively by many leading synthetic chemists to discover new classes of compounds.

Bis(imidazolium)‐1,3‐diphosphete‐diide: A Building Block for FeC2P2 Complexes and Clusters

AbstractReaction of the 6π‐electron aromatic four‐membered heterocycle (IPr)2C2P2 (1) (IPr=1,3‐bis(2,6‐diisopropylphenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ylidene) with [Fe2CO9] gives the neutral iron tricarbonyl complex [Fe(CO)3‐η3‐{(IPr)2C2P2}] (2). Oxidation with two equivalents of the ferrocenium salt, [Fe(Cp)2](BArF24), affords the dicationic tricarbonyl complex [Fe(CO)3‐η4‐{(IPr)2C2P2}](BArF24)2 (4). The one‐electron oxidation proceeds under concomitant loss of one CO ligand to give the paramagnetic dicarbonyl radical cation complex [Fe(CO)2‐η4‐{(IPr)2C2P2}](BArF24) (5). Reduction of 5 allows the preparation of the neutral dicarbonyl complex [Fe(CO)2‐η4‐{(IPr)2C2P2}] (6). An analysis by various spectroscopic techniques (57Fe Mössbauer, EPR) combined with DFT calculations gives insight into differences of the electronic structure within the members of this unique series of iron carbonyl complexes, which can be either described as electron precise or Wade–Mingos clusters.

Atomic structures and growth of monoanion germanium-vanadium glusters VGe-=SUB=-n-=/SUB=--=SUP=---=/SUP=- (n=5-19): analysis based on the Wade-Mingos rule

The paper presents the results of calculations of the spatial structure and electronic spectra of various isomers of anionic vanadium-germanium clusters VGen- (n=5-19). The calculations were carried out using three functionals --- B3LYP, B3PW91 and PBE in combination with the 6-311+g(d) basis set. Interpretation of the results of calculations of the spatial structure of clusters using data from their photoelectron spectroscopy made it possible to solve two problems at once. First, perform a Wade-Mingos rule test for a given set of clusters. Secondly, to eliminate errors in the analysis of the results and to establish the spatial structure of clusters with the greatest reliability. Keywords: atomic clusters, density functional theory, Wade-Mingos rule, electronic spectrum.

Metallo-boranes: a class of unconventional superhalogens defying electron counting rules.

Superhalogens are a class of highly electronegative atomic clusters whose electron affinities exceed those of halogens. Due to their potential for promoting unusual reactions and role as weakly coordinating anions as well as building blocks of bulk materials, there has been considerable interest in their design and synthesis. Conventional superhalogens are composed of a metal atom surrounded by halogen atoms. Their large electron affinities are due to the fact that the added electron is distributed over all the halogen atoms, reducing electron-electron repulsion. Here, using density functional theory with a hybrid exchange-correlation functional, we show that a new class of superhalogens can be developed by doping closo-boranes (e.g., B12H12) with selected metal atoms such as Zn and Al as well as by replacing a B atom with Be or C. Strikingly, these clusters defy electron counting rules. For example, according to the Wade-Mingos rule, Zn(B12H12) and Al(BeB11H12) are closed-shell systems that should be chemically inert and, hence, should have very small electron affinities. Similarly, Zn(B12H11), Al(B12H12), and Zn(CB11H12), with one electron more than needed for electronic shell closure, should behave like superalkalis. Yet, all these clusters are superhalogens. This unexpected behavior originates from an entirely different mechanism where the added electron resides on the doped metal atom that is positively charged due to electron transfer.

Heterometallic rhodium clusters as electron reservoirs: Chemical, electrochemical, and theoretical studies of the centered-icosahedral [Rh12E(CO)27]n- atomically precise carbonyl compounds.

In this paper, we present a comparative study of the redox properties of the icosahedral [Rh12E(CO)27]n- (n = 4 when E = Ge or Sn and n = 3 when E = Sb or Bi) family of clusters through in situ infrared spectroelectrochemistry experiments and density functional theory computational studies. These clusters show shared characteristics in terms of molecular structure, being all E-centered icosahedral species, and electron counting, possessing 170 valence electrons as predicted by the electron-counting rules, based on the cluster-borane analogy, for compounds with such metal geometry. However, in some cases, clusters of similar nuclearity, and beyond, may show multivalence behavior and may be stable with a different electron counting, at least on the time scale of the electrochemical analyses. The experimental results, confirmed by theoretical calculations, showed a remarkable electron-sponge behavior for [Rh12Ge(CO)27]4- (1), [Rh12Sb(CO)27]3- (3), and [Rh12Bi(CO)27]3- (4), with a cluster charge going from -2 to -6 for 1 and 3 and from -2 to -7 for cluster 4, making them examples of molecular electron reservoirs. The [Rh12Sn(CO)27]4- (2) derivative, conversely, presents a limited ability to exist in separable reduced cluster species, at least within the experimental conditions, while in the gas phase it appears to be stable both as a penta- and hexa-anion, therefore showing a similar redox activity as its congeners. As a fallout of those studies, during the preparation of [Rh12Sb(CO)27]3-, we were able to isolate a new species, namely, [Rh11Sb(CO)26]2-, which presents a Sb-centered nido-icosahedral metal structure possessing 158 cluster valence electrons, in perfect agreement with the polyhedral skeletal electron pair theory.

(CrGe9)Cr2(CO)13]4−: A disubstituted case of ten-vertex closo cluster with spherical aromaticity

We report the first disubstituted hetero-ten-vertex closo cluster [(CrGe9)Cr2(CO)13]4− with three adjacent Cr(CO)n units adopting both η5 and η1 coordination modes, which was synthesized through the reaction of “KGe1.67” with (MeCN)3Cr(CO)3 and Cr(CO)6 in ethylenediamine (en) solution. In contrast to the η1-Cr atoms forming localized two-center two-elelctron (2c-2e) Cr-Ge bonds, the hetero atom η5-Cr exhibits versatile bonding mechanisms including three 5c-2e and five 8c-2e delocalized bonds which account for Hückel aromaticity. Intricate multi-center bonding patterns delineate the multiple local σ-aromatic characters of the title cluster displaying explicit spherical aromaticity.

Binding of noble gas atoms by superhalogens.

Because of their closed shells, noble gas (Ng) atoms (Ng = Ne, Ar, Kr, and Xe) seldom take part in chemical reactions, yet finding such mechanisms not only is of scientific interest but also has practical significance. Following a recent work by Mayer et al. [Proc. Natl. Acad. Sci. U. S. A. 116, 8167-8172 (2019)] on the room temperature binding of Ar to a superelectrophilic boron site embedded in a negative ion complex, B12(CN)11 -, we have systematically studied the effect of cluster size and terminal ligands on the interaction of Ng by focusing on B12X11(Ng) (X = H, CN, and BO) and B12X10(Ng)2 (X = CN and BO) whose stabilities are governed by the Wade-Mingos rule and on C5BX5(Ng) (X = H, F, and CN) and C4B2(CN)4(Ng)2 whose stabilities are governed by the Huckel's aromaticity rule. Our conclusion, based on density functional theory, is that both the cluster size and the terminal ligands matter-the interaction between the cluster and the Ng atoms becomes stronger with increasing cluster size and the electron affinity of the terminal ligands. Our studies also led to a counter-intuitive finding-removing multiple terminal ligands can enable electrophilic centers to bind multiple Ng atoms simultaneously without compromising their binding strength.

Role of Size and Composition on the Design of Superalkalis.

Superalkalis and superhalogens are atomic clusters that mimic the chemistry of alkali and halogen atoms, respectively; the ionization energies of the superalkalis are less than those of alkali atoms, while the electron affinities of superhalogens are larger than those of the halogen atoms. These superions can serve as the building blocks of a new class of supersalts with applications in solar cells, metal-ion batteries, multiferroic materials, and so on. While considerable progress has been made in the design and synthesis of superhalogens, a similar understanding of superalkalis is lacking. Using density functional theory with hybrid exchange-correlation functional and Gaussian basis sets, we have systematically studied the role of size and composition on the properties of two different classes of clusters whose stabilities are governed by the Wade-Mingos polyhedral skeletal electron pair theory. One class belongs to the closo-borane family LimBnXn (m = 1, 2, 3; n = 6, 12; X = H, F, CN), while the other to the Zintl ions Lim[Be@Ge9]. We show that Li3BnXn and Li3[Be@Ge9] clusters are superalkalis with ionization energies as low as 2.84 eV in Li3B6H6. However, contrary to expectation, the ionization energies do not decrease with increasing cluster volume. Instead, ionization energies are linked to the X ligands' electron affinities; the larger the electron affinity, the higher is the ionization energy. The understanding gained here will help in the discovery of superalkalis and, hence, enrich the library of supersalts.

Salts of octabismuth(2+) polycations crystallized from Lewis-acidic ionic liquids

Abstract The reaction of Bi and BiCl3 with RbCl or CsCl in the Lewis-acidic ionic liquid (IL) [BMIm]Cl·4AlCl3 at T = 200 °C yielded air-sensitive, shiny black crystals. X-ray diffraction on single crystals revealed the hexagonal structures of two new salts (Bi8)M[AlCl4]3 (M = Rb, Cs), which are isostructural to the high-temperature form of (Bi8)Tl[AlCl4]3. The known (Bi8)2+ polycation is a square antiprism and can be interpreted as an arachno cluster following modified Wade rules. The crystal structure is a complex variant of the hexagonal perovskite structure type ABX 3 with A = (Bi8)2+, B = M + and X = [AlCl4]–. Chiral strands ∞ { M [ AlCl 4 ] 3 } 2 − ∞ 1 $\infty {}_{\infty }{}^{1}{\left\{M{\left[{\text{AlCl}}_{4}\right]}_{3}\right\}}^{2-}$ (M = Rb, Cs) run along [001]. The (Bi8)2+ polycations are only weakly coordinated inside a cage of 24 chloride ions and show dynamic rotational disorder at room temperature. Upon slow cooling to 170 K, the reorientation of the clusters was frozen, yet no long-range order was established.

A joint experimental and theoretical study on structural, electronic, and magnetic properties of MnGen - (n = 3-14) clusters.

A systematic structure and property investigation of MnGen - (n = 3-14) was conducted by means of density functional theory coupled with mass-selected anion photoelectron spectroscopy. This combined theoretical and experimental study allows global minimum and coexistence structures to be identified. It is found that the pentagonal bipyramid shape is the basic framework for the nascent growth process of MnGen - (n = 3-10), and from n = 10, the endohedral structures can be found. For n = 12, the anion MnGe12 - cluster probably includes two isomers: a major isomer with a puckered hexagonal prism geometry and a minor isomer with a distorted icosahedron geometry. Specifically, the puckered hexagonal prism isomer follows the Wade-Mingos rules and can be suggested as a new kind of superatom with the magnetic property. Furthermore, the results of adaptive natural density partitioning and deformation density analyses suggest a polar covalent interaction between Ge and Mn for endohedral clusters of MnGe12 -. The spin density and natural population analysis indicate that MnGen - clusters have high magnetic moments localized on Mn. The density of states diagram visually shows the significant spin polarization for endohedral structures and reveals the weak interaction between the Ge 4p orbital and the 4s, 3d orbitals of Mn.