Stable? You can bottle it! The base‐stabilized dichlorosilylene L1SiCl2 (see picture; L1=1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) is stable at room temperature. L1SiCl2 can undergo a reaction with diphenylacetylene to form a trisilacyclopentene derivative. These compounds have been characterized by X‐ray crystallography and computational studies.

New and concise descriptors of the residual density are presented, namely the gross residual electrons, the net residual electrons and the fractal dimension distribution. These descriptors indicate how much residual density is present and in what way it is distributed, i.e. the extent to which the distribution is featureless. The amount of residual density present accounts for noise in the experimental data as well as for modeling inadequacies. Therefore, the minimization of the gross residual electrons during refinement serves as a quality criterion. In the case where only Gaussian noise is present in the residual density, the fractal distribution is parabolic in shape. Deviations from this shape therefore serve as an indicator for systematic errors. The new measures have been applied to simulated and experimental data in order to study the effects of noise, model inadequacies and truncation in the experimental resolution. These measures, although designed and examined with particular regard to applications of space residual density, are very general and can in principle also be applied to space and momentum residual densities in a one-, two-, three- or higher-dimensional Euclidean space.

Two new approaches for synthesizing RSiCl, (R = PhC(NtBu)(2)) are reported by the reaction of RSiHCl(2) with bis-trimethyl silyl lithium amide and N-heterocyclic carbene respectively. In the former method silylene is produced in 90% yield. The silylene was treated with biphenyl alkyne to afford the disilacyclobutene system. This is a rare example of two five-coordinate silicon centers arranged adjacent to each other in a four-membered ring. Furthermore, we fluorinated the four-membered ring by trimethyltin fluoride to obtain the fluoro substituted disilacyclobutene.

Stabil? Man kann es abfüllen! Das basenstabilisierte Dichlorsilylen L1SiCl2 (siehe Bild; L1=1,3‐Bis(2,6‐diisopropylphenyl)imidazol‐2‐yliden) ist bei Raumtemperatur stabil und reagiert mit Diphenylacetylen zu einem Trisilacyclopentenderivat. Beide Verbindungen wurden röntgenographisch und mithilfe von Computerstudien charakterisiert.

To elucidate the bonding situation in the widely discussed hypervalent sulfur nitrogen species, the charge density distributions rho(r) and related properties of four representative compounds, methyl(diimido)sulfinic acid H(NtBu)(2)SMe (1), methylene-bis(triimido)sulfonic acid H(2)C[S(NtBu)(2) (NHtBu)](2) (2), sulfurdiimide S(NtBu)(2) (3), and sulfurtriimide S(NtBu)(3) (4), were determined experimentally by high-resolution low-temperature X-ray diffraction experiments (T = 100 K). This set of molecules represents an ideal frame of reference for the comparison of SN bonding modes, because they contain short formal S=N double bonds as well as long S-N single bonds, some of them influenced by inter- or intramolecular hydrogen bonds. For comparison, the gas-phase ab initio calculations of the four model compounds, H(NMe)(2)SMe, H(2)C[S(NMe)(2)(NHMe)](2), S(NMe)(2), and S(NMe)(3), were performed. The topological features were found to be not particularly sensitive with respect to different substituents R (R = H, Me, tBu). In this paper, it is documented that theory and experiment differ in the eigenvalues of the Hessian matrix because of systematically differing positions of the bond critical points but agree very well concerning the spatial Laplacian distribution and the distinct polarization of all investigated sulfur-nitrogen bonds. Both recommend the S(+)-N(-) formulation of sulfur nitrogen bonds in 1 and 2 since all nitrogen atoms are found to be sp(3) hybridized. The planar SNx (x = 2, 3) units in the diimide 3 and the triimide 4 reveal characteristics of m-center-n-electron systems. For none of the investigated S-N bonds, a classical double bond formulation can be supported. This is further substantiated by the NBO/NRT approach. Valence expansion to more than eight electrons at the sulfur atom can definitely be excluded to explain the bonding.

The concept of hypervalency in molecules, which hold more than eight valence electrons at the central atom, still is a topic of constant debate. There is general interest in silicon compounds with more than four substituents at the central silicon atom. The dispute, whether this silicon is hypervalent or highly coordinated, is enlightened by the first experimental charge density determination and subsequent topological analysis of three different highly polar Si-E (E = N, O, F) bonds in a hexacoordinated compound. The experiment reveals predominantly ionic bonding and much less covalent contribution than commonly anticipated. For comparison gas-phase ab initio calculations were performed on this compound. The results of the theoretical calculations underline the findings of the experiment.

It's hip to be square: The reaction of amidinato chlorosilylene (PhC(NtBu)2SiCl) with adamantyl phosphaalkyne and white phosphorus affords the formation of Si‐C‐Si‐P and Si‐P‐Si‐P (see picture) four‐membered rings. Both compounds were characterized by single‐crystal X‐ray studies and by solution and solid‐state NMR spectroscopy. DFT calculations elucidated the bonding situation.

In the present study, we employ a set of different sulfur−nitrogen compounds, which contains eight different SN bonds of varying polarity, to study descrepancies between experimentally and theoretically derived electron densities characterized by their topological properties at the bond critical point according to Bader's quantum theory of atoms in molecules approach. First, the convergency of the computationally obtained parameters with respect to the theoretical approach (flexibility of the basis sets, method of computation, influence of substituents) is presented. A comparison with the experiment is performed by a direct comparison of the theoretical and experimental counterparts and by an investigation into what extent the various data sets exhibit relationships to the nature of the bonds. This approach allows testing of the self-consistency of the theoretical and experimental data, respectively. Finally, the outcomes of the atoms-in-molecules approach is compared with results obtained from the natural bond orbital approach and natural resonance theory.