摘要:

AbstractThe principle of minimum chemical distance (PMCD) allows one to formulate the isoprene rule, the conversion of tetrahydrodicyclopentadiene into adamantane, five syntheses of colchicine, and the syntheses of C16‐hexaquinacene, morphine and strychnine as optimization problems which can be solved by computers in less than a second. The principle of minimum chemical distance is based on an algebraic theory of constitutional chemistry. The PMCD, a corollary to the well known principle of minimum structure change, is a quantitative heuristic rule which serves as the foundation of the computer‐assisted combinatorial solution of a great variety of chemical problems, particularly in substructure analysis, the study of reaction mechanism, and the design of synthe

ISSN:0570-0833    

DOI:10.1002/anie.198004953

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractTransmission electron microscopy (TEM) can be used with crystalline solids to obtain direct images of small structural groups comprising a few coordination polyhedra with resolution nearly down to atomic scale (“lattice imaging”). More exact knowledge of the conditions required for direct imaging, as well as improvements in the instruments themselves, have now made it possible to examine very small defect regions (microdomains), faults in the stacking sequence of structural groups or atom layers (planar or Wadsley defects), and isolated defects in narrowly delimited areas that may actually be below the dimensions of the unit cell. The structural principle of the very smallest ordered regions can even be determined when X‐ray structure analysis proves unable to do this. “Block structures” are particularly suitable as models for the testing and further development of the high‐resolution method; the detection of three‐dimensional, two‐dimensional, and one‐dimensional defects has been studied o

ISSN:0570-0833    

DOI:10.1002/anie.198005051

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

摘要:

AbstractIn this progress report a new principle is described for the synthesis of multimetal π‐complexes with hitherto unknown structural features. The nickel(0)‐olefin complexes 1,5,9‐cyclododecatrienenickel(0) and bis(1,5‐cyclooctadiene)nickel(0) react unexpectedly with main‐group metals, in particular alkali metals, their hydrides, and organometallic compounds, to give nickelligand species with a surplus charge. These species endeavor to transfer the excess charge onto π‐ligands such as olefins or dinitrogen. Multimetal complexes with electron rich transition metal π‐ligand units can, in addition, be prepared from metallocenes, alkali metals, and unsaturated compounds. The syntheses, structures, and reactions of this new class of substances wi

ISSN:0570-0833    

DOI:10.1002/anie.198005201

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198005381

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198005401

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198005411

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198005432

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198005451

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198005461

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.198005471

出版商:Hüthig&Wepf Verlag    

年代:1980

数据来源: WILEY