摘要:

AbstractThe coordination behaviour of p‐quinones and p‐quinone fragments in electron‐rich complexes is variable. Considering primarily the nickel triade elements, p‐quinones are bound to palladium(0) or platinum(0) by the CC‐groups (η2‐or η4‐interaction).With nickel(0) the behavior is more complicated. η4(CC)‐coordination is found for Ni(Dch)2and η2‐coordination for (dipy)Ni(Nch). But because of the stronger oxophilic properties of this element, also an η2(CO)‐coordination is possible, as was shown for (Cy3P)2Ni(Achθ•) · Et2O. In complexes with a low content of phosphine the donors R‐cum or Nch have the function of η2(CC, O)‐bridging ligands.Chloranile with its high half‐wave potential oxidises nickel(0) to nickel(II) and is simultaneously reduced to the dianion of the corresponding hydroquinone. In another case — (Cy3P)Ni(Ach⊖) — the redox process stops at the state of nickel(I) and of the radical anion. It is a general rule, that both 1,5‐cyclooctadiene as a simple diolefine and normal p‐quinones can coordinate to nickel(0) or nickel(I) as n‐acceptor ligands by the CC‐ or in the case of Ach even by the CO‐group. This is not possible with nickel(II) which is only a weak †‐donor.Tertiary phosphines attack Bch, CA, NCh or MSA nucleophilically forming phosphabetaines. Because of the lower nucleophilicity of the phosphine and the lower electrophilicity of the p‐quinone in the coordination sphere of electron‐rich central atoms this reaction does not proceed. The systems of (Cy3P)2Ni(C2H4) with CA, Bch and MSA are exceptional. In these cases the formation of phosphabetaines is connected with an one‐electron transfer. The products are nickel(II)‐species with radical anions as ligands.In general the normal reactions of p‐quinones are hindered in the coordination sphere of ele

ISSN:0044-2402    

DOI:10.1002/zfch.19890290902

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractLDPE, PVF and PP films were modified by vapour phase fluorination with oxygen‐containing fluorine (5 Vol.‐% of O2) under dynamic and static conditions. Based on measurements of total acidity on the surfaces, the permeation behaviour of n‐pentane and the chemical stability of the fluorinated films the influence of oxygen on the generation of stable barrier layers was investigated. The optimal fluorine content on the surface was found to be 3 to 5% for the 30 μm thick films. The vapour phase fluorination under static conditions has to be prefered in comparison to the fluorination under dynamic cond

ISSN:0044-2402    

DOI:10.1002/zfch.19890290903

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe paper considers complex formation and structure of phosphorus, arsenic and antimony fluorine‐containing octahedral compounds in organic solvents, aqueous and peroxide solutions, on the basis of results obtained by chemists of the USSR and G.D.R. in the course of recent year scientific cooperatio

ISSN:0044-2402    

DOI:10.1002/zfch.19890290904

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractAfter describing the main chemical reactions going on during the hydration of portland‐cement, the influence of small increases in the alkali‐ and sulphate content, coming from the introduction of new energy saving cementproduction processes, are discussed. By investigating pore‐ solutions squeezed from, hardened cement pastes it was shown that they contain alkalihydroxides up to 1 mol/l. These alkalihydroxide solutions react with some types of aggregates in the concrete giving alkalisilicate gels, which swell in the presence of humidity, resulting in crack formation and demolishing of the concrete constructions.In addition to this reaction the amount of ettringite (Ca6[Al(OH)6]2· [SO4]3· 26H2O) formed from the cement clinker mineral 3CaO · Al2O3is increased, because of the higher level of sulphate resulting from the fact, that most of the alkalies in the portland cement clinker are present as alkalisulphates. This ettringite is decomposed if the concrete is treated in the temperature range from 50–100°C to accelerate the hardening process. At room temperature ettringite crystallizes again which is accompanied by volume increase resulting in a deterioration of the concrete too. Possibilities to avoid the alkali‐aggregate reaction as well as the secondary ettringite format

ISSN:0044-2402    

DOI:10.1002/zfch.19890290905

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

ISSN:0044-2402    

DOI:10.1002/zfch.19890290906

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

ISSN:0044-2402    

DOI:10.1002/zfch.19890290907

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

ISSN:0044-2402    

DOI:10.1002/zfch.19890290908

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

ISSN:0044-2402    

DOI:10.1002/zfch.19890290909

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

ISSN:0044-2402    

DOI:10.1002/zfch.19890290910

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

ISSN:0044-2402    

DOI:10.1002/zfch.19890290911

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY