The Crystal Structure of Bi₈(AlCl₄)₂ and the Crystal Structure, Conductivity, and Theoretical Band Structure of Bi₆Cl₇ and Related Subvalent Bismuth Halides

Abstract

The methods of preparation for Bi8(A1C14)2 and Bi6C17 have been improved and the single crystal structures for these cluster compounds re-investigated and re-interpreted. In addition, conductivity measurements and band structure calculations using the tight-binding approximation have been performed on BieC17 and related subvalent bismuth halides. -Bi,(A1C14)2 consists of isolated A1C1, anions and rather undistorted square-antiprismctic Bi2+ clusters with an average Bi-Bi distance 0f~3.10 A. Relatively short intercluster Bi-Bi contacts of 3.90 A suggest weak bonding interactions between the Big+ units. In contrast, the structure determination of Bi6C17 implies that this structure should be regarded as being composed of discrete BkZ+ clusters and a polymeric Bi"'-Cl anionic lattice including infinite, distorted A[Bi2C1$+] chains. According to the experimental and theoretical results, the Bi6X7 (X = C1, Br) family of subvalent bismuth halide compounds are anisotropic semiconductors along the crystallographic c axis. The conductivity is mediated by the onedimensional &[BizCli'] chains. These are interconnected with the Bi$+ clusters, which are acting as electron resenroirs. The related BiX (X = Br, I) family of subvalent bismuth halides are shown to be anisotropic semiconductors in the crystallographic b direction. Subvalent bismuth chloride was at first formulated as BiCl[',21, but was later crystallographically shown to actually have the stoichiometry Bi6C17 and to exhibit an unusually complex structure with isolated Bi;+ clusters and chlorobismuthate(II1) c~rnplexes[~-~]. The authors described the structure as (Bi$')2(Bi2Cl$-)(BiCl~L)4, corresponding to the over-all stoichiometry Bi6C17. The 1 : 1 BiCl compound has so far not been synthesised, and it is interesting to note the following trend in the stoichiometry of the subvalent bismuth halides that have been isolated and characterized : Bi6C17Bi6Br7 BiBrAll these compounds have been structurally characterised in the solid ~t a t e [~- '~] and the Bi6X7 (X = C1 or Br) pair found to be structurally analogous. There are two main reasons for our interest in the latter two compounds. First, Bi6CI7 has been reported to be a metallic conductor, whereas the structural and chemical analogue Bi6Br7 is claimed to be an insulator [7]. Such a difference is very surprising considering the isostructurality and chemical simi-BiI Bi71Z, Bi912 larity of the two compounds. Second, the previous structural characterisations of Bi6C17 are incomplete in the sense that the chloride positions were not refined anisotropically. In this work, the crystal structure of Bi6C17 has been redetermined, and the conductivity of a single crystal determined. The new results have then been rationalised using band structure calculations.BiBr and the three different modifications of BiI are also structurally analogous and contain one-dimensional Bi2X4 double chains bridged by metal-metal bonded chains of interstitial, formally zero-valent Bi atom^ [^,^]. The more metal-rich subvalent bismuth iodide ...

The Intermetalloid Cluster Cation (CuBi8)3+

“…To day at otal of seven different polycations [10,17] and four polyanions [18] [11] [Ru(Bi 8 ) 2 ] 6 + , [12] [(Bi 5 )Ru(Bi 4 Br 4 )Ru(Bi 5 )] 4 + , [21] [(Bi 8 )Ru(Bi 4 Br 4 )Ru(Bi 5 )] 4 + , [22] and [(Bi 10 )(AuSbBi 3 Br 9 ) 2 ] [23] are examples of such complexes ( Figure 3). The calculated molecular orbital schemes corroborated the applicabilityo f1 8-electron counting rule and consequently the role of the polycations as six-electron donors (h 4 [11,12] Therefore, bismuth polycations act similart ok nown coordinating clusters or molecules such as nido-carboranes, [24] Zintl ions, [25] and arenes, [26] whereas bismuth polyanions tend to form heteroatomic clusters.…”

“…The average CuÀBi distance is 267.3(4) pm (for interatomic distances see Ta ble S1, Supporting Information) and thus about 7pms horter than the single bond in [(Me 3 Si) 2 Bi-Cu(PMe 3 ) 3 ]. [4] The average BiÀBi distance in the coordinating square face (329(2)pm) is 19 pm longer than in the isolated Bi 8 2 + , [10] buti s still 9pms horter than in the resembling [Au(Bi 8 ) 2 ] 5 + cluster (see below). [11] The average BiÀBi distances of the non-coordinating square face (308(1) pm) as well as between the square faces (310(2) pm) accord well with the isolated Bi 8 2 + polycation.…”

“…[11] The average BiÀBi distances of the non-coordinating square face (308(1) pm) as well as between the square faces (310(2) pm) accord well with the isolated Bi 8 2 + polycation. [10,12] Compared to the isolated Bi 9 5 + ion the average BiÀBi distances are shortened by 4pm, which is mostly due to the Bi 9 5 + showingt wo BiÀBi distances with al ength of 369 pm. [13] The copper(I) ion has ac lose chloride neighbor,w hich belongs to one of the [AlCl 4 ] À groups.T he CuÀCl distance of 227.9 pm is about 8pms hortert han in Cu [AlCl 4 ] [14] and suggestst hat the chloride ion acts as adonating ligand.…”

“…[10] TheCu-coordinating chloride ion shows an elongated AlÀCl bond with al ength of 219 pm indicating that the chloride's bondingv alence distributes over both cations. Similarly, the distances in the AlÀClÀAl bridge of the [Al 2 Cl 7 ] À ion are elongated to about 226 pm.…”

Substitution of Conventional High-temperature Syntheses of Inorganic Compounds by Near-room-temperature Syntheses in Ionic Liquids

“…Later, Beck et al modified the synthesis in order to improve crystal quality and to finally solve (Table 7) showed no significant difference to the published ones in terms of shape and position of the structural motifs. However, the examined crystal from the IL approach featured a fully ordered crystal structure in the polar space group P6 3 (2) 168 (7) 164 (5) 72 (8) 95 (5) 3 (7) 11 (6) 135 ( tetrahedra [37]. Since the crystallization in both synthesis routes occurs in the same temperature region, the presence of the IL seems to influence the crystal growth.…”