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Abstract

Since aromaticity [1] is not confined only to planar rings but also exists in three-dimensional systems, [2] the same should be true of homoaromaticity. [3±5] Although the 4Nþ2 H¸ckel electron-counting rule is defined for planar systems it has been applied to rationalize the properties of three-dimensional homoaromatic systems. [5] Recently, the 2(Nþ1) 2 counterpart of the H¸ckel rule [6] has been extended successfully [2e, 7, 8] to the aromaticity of three-dimensional delocalized systems with near spherical geometries: fullerenes, hydrogen and lithium clusters, as well as some well-known closoboranes and Zintl ions. It was found that the highest degree of aromaticity can only be achieved in systems with fully filled valence shells. We now present new conceptual applications of this electron-counting rule to three-dimensional homoaromatic systems with cubane, dodecahedrane, and adamantane frameworks. Families of spherical homoaromatics with both two and eight mobile electrons (including several neutral ZUSCHRIFTEN

[Ga51(PtBu2)14Br6]3−: ein elementoider Galliumcluster mit metalloiden und nichtmetalloiden Strukturelementen

“…Da eine zuverlässige Rechnung mit dem P t Bu 2 ‐Rest noch nicht möglich ist, wird hier auf eine weitere Diskussion verzichtet. Als bisheriges Resümee kann jedoch festgehalten werden, dass die 71 Ga‐ und 31 P‐NMR‐Verschiebungen nicht in einfacher Weise wie in den einschaligen Clustern C 60 ,14 B 12 H 12 2− 15 oder Pb 9 4− 16 durch ihre NICS‐Werte und ihre sphärische Aromatizität zu deuten sind. Vielmehr zeigt sich in diesem mehrschaligen metalloiden Cluster, dass z.…”

[Ga51(PtBu2)14Br6]3−: An Elementoid Gallium Cluster with Metalloid and Nonmetalloid Structural Elements

“…Because reliable calculations are not yet possible with the PtBu 2 group, we will refrain from further discussion at this point. However, given the current data, it is possible to conclude that, unlike in the single-shelled C 60 , [14] B 12 H 12 2À , [15] or Pb 9 4À [16] clusters, the 71 Ga and 31 P NMR chemical shifts for our clusters cannot be simply interpreted through their NICS values and their spherical aromaticity. On the contrary, in these multishelled metalloid clusters we see that the 71 Ga signal for the central Ga atom, for example, is shifted significantly (e.g.…”

“…The arrangement of the [Ga 51 (PtBu 2 ) 14 Br 6 ] 3À cluster anions 1 a in the crystals of 1 is shown in Figure 4. The roughly 2 nm clusters are in a slightly distorted cubic closepacked arrangement, in which all of the tetrahedral holes are filled with [Li(THF) 4 ] + ions and all of the octahedral holes with [Li 2 Br(THF) 6 ] + ions.…”

“…A metastable solution of GaBr in toluene/THF (3:1) was heated from À78 to À35 8C, [1,6] to induce the disproportionation to form metal-rich clusters and GaBr 3 . Subsequently, a slight excess of LiPtBu 2 suspended in toluene was added, and the reaction mixture was heated to 60 8C for 2 h. After several days in a drying oven at about 50 8C, compound 1 crystallizes as black rhombuses, which contain one [Li 2 Br(THF) 6 ] + and two [Li(THF) 4 ] + ions, as well as the anionic cluster [Ga 51 (P-tBu 2 ) 14 Br 6 ] 3À (1 a). The crystal structure analysis [7] shows that 1 a is a metalloid cluster with 31 "naked" and 20 ligandbearing Ga atoms.…”

Structure and Bonding in [Sb@In8Sb12]3− and [Sb@In8Sb12]5−

“…12 In contrast, completely inorganic clusters with Th symmetry have not yet been isolated in the condensed phase, although this symmetry has been proposed for the [Ti8C12] + cluster, observed as a "super-magic" peak in the mass spectra of mixtures of Ti and CH4 or acetylene. 13 A Th-symmetric isomer of dodecatetrahedrene, C20H12, 14 has also been the subject of computational studies, although it is substantially less stable than alternative isomers with localized C=C bonds, so is unlikely to be amenable to isolation. In this paper, we report the synthesis and characterization of an unprecedented all-metal Thsymmetric cluster, [Sb@In8Sb12] 3-, which accommodates a Sb atom at the center of an In8Sb12 cage (Figure 2).…”