摘要:

AbstractAlmost all main group and subgroup metals are able to form metal‐metal bonds. The bond order ranges from weak interaction to a quadruple bond, and the degree of aggregation from a dinuclear entity to a three‐dimensional network. In spite of numerous physicochemical studies, not all aspects of the metal‐metal bond are understood. The ability of metal‐metal linked polynuclear complexes to serve as a reservoir for missing or excess electrons enables them to react both with nucleophilic or reducing reagents and with electrophilic or oxidizing reagents. The intermediate position occupied by clusters between simple complexes and the bulk metal is of theoretical and practical signi

ISSN:0570-0833    

DOI:10.1002/anie.197803793

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractA variety of general methods is available for the synthesis of tetrahedral heteronuclear cobalt clusters of type (CO)9Co3E(L)n(E=hetero element). The size of E has a limiting effect on the existence of such complexes. No compounds (CO)9Co3E(L)nhave so far been prepared in which the covalent radius of E exceeds 1.30 Å;. Elements such as In, Sn, Pb, Sb, or Bi do not fit into the tetrahedral Co3E cluster unit and form open complexes E[Co(CO)4]n(n=3, 4). Structural variations among the heteronuclear clusters are encountered in the presence or absence of carbonyl bridges between the cobalt atoms: hetero atoms E bearing several ligands L favor bridging, whereas those bearing only one ligand or none at all permit terminal bonding of all the CO groups

ISSN:0570-0833    

DOI:10.1002/anie.197803921

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractThe charges on metal atoms and ligands in complex compounds of transition metals may be calculated theoretically or measured empirically, but there is no reliable method of doing either. This review is concerned mainly with two experimental methods, dipole moment measurement and X‐ray photoelectron spectroscopy, applied to tertiary phosphate and such complexes of the heavier transition metals. It is concluded that the charge is rarely greater than ±0.3e and that some so‐called neutral or positive ligands,e.g.N2or NO+, may carry more negative charge in a complex than formally anionic ligands such as H−. Small ligands of high formal charge,e.g.O2−, NR2−, and N3−, appear to carry no more negative charge than Cl−, but monoanionic ligands vary greatly in their capacity to contribute to the dipole moments. The ligands NO, CO, PF3, CH 3−, and H−are all nearly neutral to slightly negative, whereas pyridines, tertiary phosphanes,etc.are the most strongl

ISSN:0570-0833    

DOI:10.1002/anie.197804001

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractHemoglobin transports oxygen in the blood and is responsible for its red color. Being one of the most closely studied proteins, it is entitled an “honorary enzyme”. This admirable natural substance invites chemists to copy it, imitate it, and vary or modify it. The first means a total synthesis of the original molecule, but such reproduction does not increase our knowledge of its function. In the case of imitation, the biochemical effect of the “original” (i.e.hemoglobin) is achieved in full or in part with simpler molecules of similar structure,i.e.with models. Research is here directed at the function of hemoglobin. In the case of variation or modification the original molecule is changed to various extents, which reveals the factors underlying its action. In all three cases—reproduction, imitation, and modification—hemoglobin serves as an inspiration for research. The aim of the present review is to summarize recent investigations inspired by hemoglobin in the field of coordination chemistry. A brief outline of the coordination chemistry of the porphin system serves as an i

ISSN:0570-0833    

DOI:10.1002/anie.197804071

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

摘要:

AbstractThe mode of ionization of a molecule has a strong influence on its behavior in the mass spectrometer and thus on the information that can be obtained from its mass spectrum. In chemical ionization a reagent gas,e.g.methane, is first ionized by electron impact. The ions formed in ion‐molecule reactions, in particular [CH5]+, [C2H5]+, and [C3H5]+, then react “chemically” with the substrate M in fast acid/base type reactions to form ions of the type [MH]+, [M(C2H5)]+,etc., which subsequently fragment to various extents. Alternatively, chemical ionization can be effected by charge exchange, in that ions of a reagent gas,e.g.[He]+•, react with the substrate M to form molecular ions [M]+·. Chemical ionization can thus be conducted in a more or less mild fashion and the extent of the fragmentation can be controlled over a very wi

ISSN:0570-0833    

DOI:10.1002/anie.197804241

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197804401

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197804411

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197804421

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197804431

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY

ISSN:0570-0833    

DOI:10.1002/anie.197804441

出版商:Hüthig&Wepf Verlag    

年代:1978

数据来源: WILEY