The approach of two atoms with an unpaired electron each results in the formation of a σ bond. Snapshots of the primary step with a large atom‐to‐atom distance and a parallel spin of both electrons and of the final product, consisting of a butterfly structure with a short AlAl σ bond, have been identified for a [R2PAl(PR2)AlPR2] compound using quantum chemical calculations and X‐ray crystallography (see scheme).

Recently, compounds containing metal-metal bonds between main-group elements have attracted interest to a surprising extent. [1][2][3][4][5] In spite of the latest structural results for two crystalline Mg 2 R 2 compounds (R1 = [ArNC(NiPr 2 )NAr] À ; R2 = [{ArNCMe} 2 CH] À ; Ar= 2,6-diisopropylphenyl, iPr = isopropyl) [2] and in spite of a number of theoretical contributions on molecules with MgÀMg bonds, [10][11][12] several important questions still remain to be answered, for example, concerning the unexpected disproportionation stability of the abovementioned Mg I compounds. Herein, we present the following results: 1) On the basis of quantum-chemical-assisted thermodynamic calculations, a feasible synthesis of radical monomeric Mg I halides at temperatures near 900 8C is presented.2) The nature of the MgÀMg bond is investigated by spectroscopic examination of MgCl and its linear dimer Mg 2 Cl 2 in solid inert-gas matrixes; the MgÀMg dissociation energy is obtained. 3) By comparing the thermodynamics of Mg 2 Cl 2 (1), Mg 2 Cp 2 (2, Cp = cyclopentadienyl), and a model compound Mg 2 R* 2 (3, R* = C(NH 2 )(NCH 3 ) 2 ) analogous to crystalline Mg 2 (R1) 2 , the enormous disproportionation stability of the latter compound is explained. For further investigations, for example in the field of metal-rich Mg n R m clusters (n > m), the synthesis of reactive starting materials like MgCl is absolutely necessary. Initial results on the synthesis of MgCl are reported.After the first evidence for stable alkaline earth

Lipase was covalently attached to multiwalled carbon nanotubes (MWNTs). Structural changes of the lipase upon attachment onto MWNTs were analyzed through circular dichroism and FTIR spectroscopy. The conjugate was utilized for the resolution of a model compound (R,S)‐1‐phenyl ethanol, and the reaction medium was n‐heptane. The enzymatic resolutions were carried out at temperatures from 35 to 60°C. The results show that the lipase attached onto MWNTs has significantly affected the performance of the enzyme in terms of temperature dependence and resolution efficiency. The activity of MWNT–lipase was less temperature‐dependent compared with that of the native lipase. The resolution efficiency was much improved with MWNT–lipase. MWNT–lipase retained the selectivity of the native lipase for (R)‐1‐phenyl ethanol. The consecutive use of MWNT–lipase showed that MWNT–lipase had a good stability in the resolution of (R,S)‐1‐phenyl ethanol. © 2010 American Institute of Chemical Engineers AIChE J, 2010

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The outstanding position of metalloid clusters as intermediates between the bulk metals and bulk salts on the one hand and of naked metal atom clusters and salt-like clusters on the other hand is described first. Subsequently, a different more chemical description of structure and bonding of a recently published gold-thiolate Au 102 (SR) 44 cluster based on the results of aluminum-/gallium clusters is presented. This comparison shows that there is no principal but only a gradual difference between the Au 102 cluster and the large number of metalloid aluminum-/gallium clusters: both have a metalloid character, i.e. there is a highly mixed valent bonding situation of the metal atoms involved. Therefore these clusters represent a highly complex system and are far from being only nanoscaled metal particles surrounded by a shell of protecting ligands. In detail this comparison shows that the metalloid gold and the aluminum-/gallium clusters are similar in the center, as these metal-metal interactions are energetically similar to those of the

The highly energetic molecule Al(4)H(6), with its distorted tetrahedral structure, was recently characterized via mass spectrometry and photoelectron spectroscopy investigations (Li, X.; et al. Science 2007, 315, 356). Here we present the preparation and structural investigation of the first analogous Al(4)R(6) cluster compound. In order to understand the bonding in this kind of Al(4) molecule, density functional theory and second-order Møller-Plesset perturbation theory calculations were performed. The results obtained are discussed in comparison with bonding in other Al(4) moieties, especially the aromatic bonding behavior in the dianionic planar Al(4)(2-) species (Li, X.; et al. Science 2001, 291, 859). Finally, on the basis of the results obtained for Al(4) species, a more general problem is discussed: the difference in bonding between Zintl ions and metalloid clusters.

Magnesium bromide radicals have to be prepared as high-temperature molecules and trapped as a metastable solution because a seemingly simple reduction of donor-free Grignard compounds failed. However, the essential role of magnesium(I) species during the formation of Grignard compounds could be demonstrated experimentally.

Verbindungen mit Metall-Metall-Bindungen der Hauptgruppenelemente haben in jüngster Zeit eine unerwartet hohe Aufmerksamkeit erfahren. [1][2][3][4][5] Trotz der jüngsten strukturellen Befunde zu zwei kristallinen Mg 2 R 2 -Verbindungen (R1 = [ArNC(NiPr 2 )NAr] À ; R2= [{ArNCMe} 2 CH] À ; Ar= 2,6-Diisopropylphenyl, iPr = Isopropyl) [2] und trotz zahlreicher theoretischer Studien zu Molekülem mit Mg-Mg-Bindungen [10][11][12] Nachdem sich vor gut 50 Jahren der erste Hinweis auf stabile Erdalkali(I)-halogenide als Irrtum erwiesen hatte, [13] gelang vor knapp 40 Jahren der erste ESR-spektroskopische Nachweis unter anderem von MgF in einer Edelgasmatrix. [18] Hierzu wurde MgF 2 bei 1250 8C verdampft, die gasförmigen MgF 2 -Moleküle bei 2350 8C zu MgF und F-Atomen dissoziiert und anschließend in der Matrix abgeschieden.[19] Um zu einem für Synthesestudien praktikablen Verfahren analog zur AlCl-Synthese bei 900 8C zu gelangen, [6]