摘要:

AbstractGuided by the symmetry in a natural way, periodic potential surfaces partition the space in solid crystalline compounds. The arrangement of atoms, clusters and molecules obviously follows the (in general) curved shape of these ‘space partitioners’. In structures, the atoms therefore choose only a very limited subset of the infinite set of possible positions. In collective structures the periodic surfaces separate areas of different interactions between atoms, clusters, and molecules. In a certain sense, they can be considered as inner surfaces, a knowledge of which reveals insights into the organization of crystalline matter. There are many good indications that the weakly bonded electrons in the highest occupied orbitals are preferably localized in the region of the space partitioners. Dynamic processes as well can be correlated to the shape of the periodic surfaces. Moreover, the surfaces are didactically very helpful in making accessible the complicated three‐dimensional relations in collective structures because the main features are projected onto (although curved) two‐dimensional creations. The application of periodic potential surfaces to such a variety of compounds as quartz, brass and alpha‐amylose underscores their general significance. Simple qualitative considerations already reveal the manifold relations to animate and inanimate nature through to mathematics, art and architecture. It appears that, in a very universal sense, the adaption of structures to a collective order finds a natural solution through

ISSN:0570-0833    

DOI:10.1002/anie.198710593

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractFluorine, by far the most reactive of the non‐metals, is capable of forming a large number of compounds with nearly all other elements (exceptions (so far): He, Ne, and Ar), even under comparatively “mild” reaction conditions. These compounds usually differ markedly from those of the heavier halogens in composition, structure, and chemical and physical properties. Thus, for example, it is generally quite easy to prepare fluorides containing elements in high oxidation states (often their maximum), as in AgF2, CsAgF4, PdF3, CsAuF6etc., whereas the corresponding chlorides, bromides or iodides are in many cases (still) unknown. Conversely, the synthesis of fluorides containing these elements in middle or low oxidation states often meets with considerable difficulty, even where it is possible at all, as, e.g., in the case of CuF, AuF, PtF2, SeF2. Finally, there are also some examples of compounds MXn, which with X = F are stable, but with X = Cl are unstable or decompose easily (e.g. CoF3/CoCl3, VF4/VCl4, PbF4/PbCl4, AsF5/AsCl5). Consequently, fluorine compounds are of great general int

ISSN:0570-0833    

DOI:10.1002/anie.198710811

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractThe distinction between valence electrons and essentially inactive core electrons is the basis of many classifying concepts in chemistry. However, it has recently been recognized that this is an oversimplification and should, at least in some areas of chemistry, be modified. Many cases are known where cations with closed d10configurations are subject to homoatomic interactions that influence structure and properties. A characteristic and surprisingly uniform structural feature (e.g., of a number of compounds containing monovalent coinage metals) is a clusterlike assembly of d10cations that corresponds in geometry and bond lengths to fragments of the metal structures themselves. Further evidence for a special type of bonding in such compounds is provided by their physical properties; for example, the absorption in the UV/VIS region shows a drastic redshift and the compounds are often conductors or semiconductors. The d electrons in such cases have obviously lost their pure “core” nature. All bonding models so far proposed for such systems involve mixing of higher orbit

ISSN:0570-0833    

DOI:10.1002/anie.198710981

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractCarbosilanes are compounds in which the elements carbon and silicon occupy alternate positions in the molecular framework. Formal replacement of every second carbon atom in the diamond lattice by a silicon atom gives silicon carbide, which exists, however, in several modifications characterized by different stacking orders. The SiC lattice is the basis of most carbosilanes.[1]These are divided on the basis of structural differences into carborundanes, silascaphanes, and molecules that no longer contain elements of the silicon carbide structure. In the carborundanes the Si–C six‐membered rings are arranged in the chair form, in the silascaphanes in the boat form. The molecular framework of the third group is derived from barrelane and asterane. The reactivity of the carbosilanes is determined mainly by the substituents on the skeletal atoms. The presence of SiH or Si–halogen groups leads to a high reactivity, while derivatives with organic groups on the silicon atoms and CH2or CH groups in the skeleton are much less reactive. However, even such CH2and CH groups permit certain characteristic reactions. Because of their structural features and the range of substituents that can be introduced, the carbosilanes are presently of considerable interest with respect to technological developments as precursors for cer

ISSN:0570-0833    

DOI:10.1002/anie.198711111

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198711331

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198711341

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198711411

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198711431

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198711451

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198711461

出版商:Hüthig&Wepf Verlag    

年代:1987

数据来源: WILEY