A Metalloid [Ga₂₃{N(SiMe₃)₂}₁₁] Cluster: The Jellium Model Put to Test

Abstract

Dedicated to Professor Helge Willner on the occasion of his 60th birthdayDepicting the electronic structure of compounds clearly is one of the most difficult tasks in chemistry. For molecular moieties of identical atoms (clusters) many models have been developed which are often limited to specific compound classes. Gaseous cluster species, for example, as ions in mass spectrometry, could suitably be described with the Jellium model because the filling of electronic shells in these species, like in atoms, with specific numbers of valence electrons can explain their different stabilities.[ (Figure 1). [6,7] The rules of Wade, [9] Mingos, [10] Zintl, [11] Klemm, [11] and Jemmis, [12] for example, were useful in the explanation of bonding found in the structurally characterized cluster species of boranes or Zintl ions. But these models can only rudimentarily be applied to larger cluster species of identical metal atoms [13] (for example [Al 77 R 20 ] 2À ). The topological similarity in the arrangement of metal atoms of these clusters with the one found in elements was our motivation for terming such species metalloid or even elementoid clusters. [14,15] Recently King and Schleyer could show that some of the mentioned rules can in fact be used in the bond description of such a metalloid [Ga 22 R 8 ] cluster (Figure 1). [16] Herein, we attempt to demonstrate that the Jellium model can also contribute to the understanding of several metalloid clusters. These considerations are now possible for the first time because a unique possibility of comparison for a single element is given by a {Ga 23 } cluster presented here and four further differently structured {Ga 22 } clusters, [17] as well as a recently reported {Ga 24 } cluster [8] (Figure 1). The capacity of the Jellium model to describe the bonding of such clusters can be assessed based on experimental structural data. For the discussion on the bonding situation special attention will be given to the atomic volumes.At À78 8C a suspension of LiN(SiMe 3 ) 2 in toluene was treated with a small excess of a metastable GaCl solution in toluene/ether (3:1) that was obtained by the joint condensation of GaCl molecules formed at about 900 8C and the solvent mixture.[18] After processing the reaction solution (see the Experimental Section) black rhombus-shaped crystals of the title compound [Ga 23 {N(SiMe 3 ) 2 } 11 ] (1) were obtained. [19] Thus, formally, disproportionation and subsequent or simultaneous metathesis of GaCl occurred in the reaction.The result of the X-ray structural analysis of 1 is presented in Figure 2 a.[20] A body-centered naked {Ga 12 } core is present in 1 and is surrounded by 11 GaR moieties. The most important structural data are shown in the caption of Figure 2, where 1 is contrasted with the similar cluster [Ga 22 {N(SiMe 3 ) 2 } 10 ] 2À (2).[21] Both clusters contain a central Ga atom uncommonly surrounded by 11 further "naked" (that is, not ligand-bearing) gallium atoms.[22] The ligand shell of 1 is formed by 11 GaR moieties, and that of 2 is for...

Hund’s rule in superatoms with transition metal impurities

“…There are several approaches to make cluster assemblies from superatoms. One could isolate clusters by passivating them with organic ligands (14,15), insert them into zeolite cages (33), or deposit them on substrates (34). Forming assemblies through direct deposition on substrates, however, requires the magnetic features to be maintained through the assembly.…”

“…Further Al 13 has a large electron affinity of 3.4 eV close to that of a Cl atom (9). These analogies have prompted the concept that selected stable clusters could mimic the electronic behavior of elemental atoms and be classified as superatoms forming a third dimension of the periodic table (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). Because the properties of clusters change with size and composition, the superatoms offer the prospect of serving as the building blocks of nanomaterials with tunable characteristics (16,18).…”

A unified view of ligand-protected gold clusters as superatom complexes

“…This theory has been successful explaining the mass abundances of uncoordinated gas-phase metallic clusters (4), gas-phase metallic clusters coordinated with a small number of simple ligands (5-7), and Ga-based ''metalloid'' clusters (8). It has also been speculatively proposed (9) as a possible explanation for the compositions of the distinct thermodynamically stable cluster sizes of various monolayer-protected metal clusters that form by a selforganized process in solution.…”

“…The predictive value of the simple arithmetic embodied in Eq. 2 has been demonstrated in the case of gas-phase metallic clusters coordinated with small numbers of simple ligands (5-7) and for Ga-based metalloid clusters (8). However, it has been challenging to adapt the similar arithmetic for ''solution''-phase clusters, which besides satisfying expressions 1 and 2 must also have a sterically complete protective ligand shell compatible with a compact atomic shell structure for the metallic core.…”

[Ga24Br18Se2]: ein hochsymmetrischer metalloider Cluster und seine eindimensionale Anordnung im kristallinen Zustand als Modell für photoleitendes festes GaSe

“…Die vorgelegten Ergebnisse weisen sowohl für die Einzelcluster von 3 als auch für ihre Anordnung im Kristall auf einige bemerkenswerte Besonderheiten hin: Die Strukturen von metalloiden Einzelclustern lassen sich durch so verschiedene Modelle wie das Wade-Konzept, [23,24] das JelliumModell [25] oder durch die topologische Nähe zu den Elementstrukturen (elementoide oder metalloide Cluster) [7,26] plausibel machen. Im Fall von 3 spielt offensichtlich eine besondere Stabilisierung im Kristall über ungewöhnliche SeSe-Wechselwirkungen eine Rolle; offenbar werden Topologie und Stabilität solcher Cluster in bisher noch nicht verstandener Weise durch viele Faktoren unterschiedlicher Gewichtung beeinflusst.…”