摘要:

AbstractThe possibility to excitedirectlyat 185 nm chromophores that absorb in the vacuum‐UV has stimulated increased activity during the last decade in this field of photochemistry. Whereas photochemical reactions at λ220 nm), 185‐nm irradiation preferentially results inintramolecularrearrangement, fragmentation, and isomerization reactions. Intermolecular radical couplings and abstractions as well as dimerizations (π, π*‐excitation) compete minimally. Besides the straightforward denitrogenation of photoresistant (“reluctant”) azoalkanes, important applications of the short‐wavelength photolysis are also found in technology (photolithography) and medicine (193‐nm laser). Broadening the scope of the synthetic potential of the 185‐nm photochemistry, which so far has been limited to directcis/transisomerizations, presents a ch

ISSN:0570-0833    

DOI:10.1002/anie.198606613

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractIn order to understand the dynamics of chemical reactions in general, detailed information on electronic, structural and kinetic properties is required. The key questions on how chemical reactions actually occur can in many cases only be answered in terms of information obtained from kinetic studies. In conventional kinetic studies of chemical reactions in solution, the variables usually selected include concentration, acidity, solvent, and temperature. In recent years, pressure has become an additional selected variable in such studies. It enables the measurement of the volume of activation and the construction of reaction volume profiles and thus assists in the elucidation of the underlying mechanism; it also completes the comprehension of reaction kinetics by adding another kinetic parameter that the suggested reaction mechanism must account for. Furthermore, the volume of activation is the only transition state property that can be correlated with the corresponding ground state property in an experimentally simple manner. In this paper, the insights so gained in our understanding of the dynamics of reactions involving coordination complexes will be presented. Such reactions are of fundamental interest to chemists since they often form the basis of catalytic, biological, environmental and energy related processes. Any additional information that will add to the understanding of the reaction dynamics is therefore of exceptional importance.

ISSN:0570-0833    

DOI:10.1002/anie.198606731

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe electrochemical formation and regeneration of redox agents for organic syntheses (indirect electrolysis) widens the potential of electrochemistry, as higher or totally different selectivities can often be obtained while at the same time the energy input can be lowered significantly. Higher current densities can also be obtained by preventing otherwise often encountered electrode inhibition. New types of redox catalysts can be formed in‐situ and can be regenerated after reaction with the substrates. This principle is of increasing importance also for the application of already known redox agents with regard to environmental protection, since large amounts of a product can be generated in a closed circuit using only relatively small amounts of the redox reagent. Consequently the operation of such a process can be greatly simplified, and the release of ecologically objectionable spent reagents into the environment can be prevented. The broad spectrum of redox catalysts currently in use includes, inter alia, metal salts in very low or high oxidation states, halogens in various oxidation states, and, in particular, a wide variety of transition‐metal complexes. A great deal of progress has recently been made in the application of organic electron transfer agents, since compounds have been found that are sufficiently stable in both the reduced as well as the oxidized st

ISSN:0570-0833    

DOI:10.1002/anie.198606831

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractMetallocenophanes are metallocenes in which the cyclopentadienyl ligands are linked intramolecularly through CmHnor CmHnX (X = heteroatom) chains. Two main classes of metallocenophanes are known: in [m]metallocenophanes the ligands ofonemetallocene are connected by a bridge (or by several bridges); in [m.n]metallocenophanestwo(or more) metallocenes are brought together into one molecule by bridging groups. This article briefly describes the first class (mononuclear complexes) and then concentrates on the second (binuclear complexes). The [1.1]metallocenophanes, which are produced by linking two metallocene moieties through two C1, bridges, are of particular interest and are characterized by a variety of unusual and useful properties: they are very flexible conformationally; hydride abstraction from the CH2bridges produces carbenium ions that are greatly stabilized by the adjacent metallocene moieties; deprotonation of one of the CH2bridges is surprisingly easy and leads to the unusual situation that an intramolecular CHċC hydrogen bond stabilizes a carbanion; protonation of both metallocene moieties causes the liberation of one mole of hydrogen per mole of [1.1]metallocenophane, thereby allowing the use of these compounds as catalysts for the formation of hydrogen in acidic aqueous solutio

ISSN:0570-0833    

DOI:10.1002/anie.198607021

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198607181

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198607191

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198607201

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198607231

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198607251

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198607271

出版商:Hüthig&Wepf Verlag    

年代:1986

数据来源: WILEY