Andreas Schnepf

Dative Bonds in Main‐Group Compounds: A Case for Fewer Arrows!

Risky business? The use of dative bonds to describe the electronic structure of main-group compounds has come into vogue in recent years. But where are the limits? When does the description as a dative bond make sense and when is this view misleading? This Essay develops the idea on the basis of current examples.

Dative or not dative

The critique on our Essay Dative Bonds in Main-Group Compounds: A Case for Fewer Arrows! [1] by Prof. Gernot Frenking (GF) (Dative Bonds in Main Group Compounds: A Case for More Arrows) gives us the opportunity to clarify some points. First of all, we refuse a single-sided notation on principle when a balanced view from different sides is necessary for complete understanding. This was the central issue behind our Essay. Formal versus partial charges: The fact that, as mentioned by GF, Lewis structures and their formal charges ”do not provide direct information about the actual charge distribution in a molecule” is taught to “every student in a freshman chemistry course” in T bingen and Freiburg as well as in Marburg and supposedly everywhere. However, Lewis formulae with formal charges can point to a polarization component, which amends the charge distribution expected based on electronegativities. A textbook example is the molecule DC OD, in which the negative formal charge at C hints to a carbon atom that—in contrast to the carbon atom in acetone or CO2—is not positively polarized. For bonds with a more ionic character, one may also consider resonance structures in which some of the atoms are not covalently bonded, for example, in [BF4] (Figure 1).

Au108S24(PPh3)16: A Highly Symmetric Nanoscale Gold Cluster Confirms the General Concept of Metalloid Clusters

The reduction of (Ph3 P)AuCl with NaBH4 in the presence of HSC(SiMe3 )3 , leads to one of the largest metalloid gold clusters: Au108 S24 (PPh3 )16 (1). Within 1 an octahedral Au44 core of gold atoms arranged as in Au metal is surrounded by 48 oxidized Au atoms of an Au48 S24 shell, a novel building block in gold chemistry. The protecting Au48 S24 shell is completed by additional 16 Au(PPh3 ) units, leading to a complete protection of the gold core. Within 1 the Au-Au distances get more molecular on going from the center to the ligand shell. Cluster 1 represents novel structural motives in the field of metalloid gold clusters which also are partly typical for metal atoms in metalloid clusters: Mn Rm (n>m).

[Ge12{FeCp(CO)2}8{FeCp(CO)}2]: A Ge12 Core Resembles the Arrangement of the High‐Pressure Modification Germanium (II)

This borderland is ofparticular interest especially for metals or semi-metals, asdrastic changes in the physical properties take place duringthe reduction from salt-like oxidized compounds (e.g. oxides,halides: non-conducting) to the elemental bulk phase (metal:conducting; semi-metal: semiconducting).

Characterisation of Germanium Monohalides by Solid-State NMR Spectroscopy and First Principles Quantum Chemical Calculations

Germanium(i) monohalides are useful starting materials to synthesise small, well defined germanium nanoclusters. However, due to the amorphous nature of solid GeBr and GeCl, details of their solid-state structures remain largely unknown. We investigate the arrangement within these novel binary materials using 35Cl, 79Br, and 73Ge solid-state NMR spectroscopy at 21.1 T and first principles quantum chemical calculations in order to suggest a possible model for the structure.

6,6′,11,11′-Tetra((triisopropylsilyl)ethynyl)-anti-[2.2](1,4)tetracenophane: a covalently coupled tetracene dimer and its structural, electrochemical, and photophysical characterization

[2.2]-Acenophanes are a class of compounds with two acene units interconnected by two ethano bridges. Due to the short bridges, the two acene subunits are in close proximity and can result in a modification of properties compared to the monomeric acene. We describe the synthesis of the first example of a [2.2](1,4)tetracenophane that is modified by four (triisopropylsilyl)ethynyl substituents and its characterization by a number of techniques including single crystal X-ray crystallography. The tetracene moieties are found to be essentially parallel to each other in the molecule. The packing is characterized by the formation of a staircase arrangement with a weak overlap between individual tetracenophane molecules. Optical spectroscopy and electrochemical investigations indicate that the two tetracene moieties of the tetracenophane communicate more than the individual pentacene units in the larger pentacenophane.

Chemistry applying metalloid tin clusters

GRAPHICAL ABSTRACT ABSTRACT Starting from Sn(I) halides, available via a preparative co-condensation technique, we have established a fruitful route to metalloid tin clusters in recent years. Applying a Sn(I)Cl solution, we were able to obtain the open anionic metalloid tin cluster [Sn10[Si(SiMe3)3]4]2− 1 in high yield. In 1 the tin atoms are incompletely shielded by the ligand shell so that subsequent reactions seem possible. Hence, a first step toward a chemistry applying metalloid tin clusters was done and we describe first investigations concerning the formation of 1 and its reactivity.

CCDC 1472908: Experimental Crystal Structure Determination

Related Article: Matthias Kotsch, Christian Gienger, Claudio Schrenk, Andreas Schnepf|2016|Z.Anorg.Allg.Chem.|642|670|doi:10.1002/zaac.201600137