摘要:

The development of methodology for synthesizing new materials in which metal atoms are linked by hydrocarbons whose electronic conjugation is unbroken is described. The fundamental idea is to twist the hydrocarbons into helices. By attaching bulky groups to their precursors, the helices can be made to twist mainly in one direction. The molecules synthesized are helicenes capped by five-membered rings to which metals are attached. If the size of the helix is chosen appropriately, a polymeric structure forms in which hydrocarbon rings and metal atoms alternate. An oligomer with Structure22is the first such material prepared. It and related structures might be precursors of molecular solenoids, examples of which are not yet known.

ISSN:0022-233X    

DOI:10.1080/00222338908051976

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The present status of research in the field of macromolecules/transition metal complexes is critically reviewed on the basis of selected examples both from the authors′ laboratories and other laboratories around the world. The substantial lack of inertness of the polymeric ligand (the polymer effect) is examined and shown to occur in most cases during preparation of the macromolecule/transition metal complex as well as during its catalytic use. This behavior is attributed and confirmed as due to the polydentate ligand character of the macromolecules and to the effect of physical and chemical parameters which can be varied over large ranges. Future work is duscussed for the development of the field in suitable directions.

ISSN:0022-233X    

DOI:10.1080/00222338908051977

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A series of polysiloxane-bound platinum complexes was prepared by the reaction of chloroplatinic acid with silica-supported polysiloxane ligands containing Sand -COOH (D) groups. These were tested as catalysts for the hydrosilylation of acetylene and olefins with functional groups, with the aim of synthesizing organosilicon monomers and silane coupling agents. It was found that supported platinum Catalyst A was an active catalyst for the hydrosilylation of acetylene and allyl chloride by dichloromethylsilane or trichlorosilane. By these catalytic reactions, several useful organosilicon monomers, such as dichloromethylvinylsilane and 3-chloropropyl-trichlorosilane, were obtained in good yield. Supported platinum Catalysts B, C, and D proved to be effective for the hydrosilylation of allyl glycidyl ether by trimethoxysilane to yield an important silane coupling agent, 3-glycidoxypropyltrimethoxysilane. The stability of supported Catalyst A is reported.

ISSN:0022-233X    

DOI:10.1080/00222338908051978

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Three types of polymeric metallocarbenes were synthesized: heterocarbene, diarylcarbene, and alkylidene complexes. They were thermally more stable than their low molecular weight analogs. They exhibited13C-NMR signals for the carbene carbons at very low magnetic field. They were characterized by typical metallocarbene reactions, such as nucleophilic substitution and oxidation, as well as cyclopropanation of unsaturated carboxylates. Thus, metallocarbenes, as an important category of organometallic compounds or intermediates, have gained entry to polymer chemistry.

ISSN:0022-233X    

DOI:10.1080/00222338908051979

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Inclusion compounds of transition metal complexes of cycloocta-1,5-diene (cod) and norbornadiene (nbd) with cyclodextrins were prepared. Two-to-one (cyclodextrin:guest) inclusion compounds were obtained in high yields by the treatment of β-cyclodextrin (β-CD) with [(L)RhCl]2(L = nbd or cod) and 1:1 inclusion compounds were obtained by the reaction of β-CD with (cod)PtX2(X = Cl, Br, or I) in high yields, while γ-CD formed 1:1 inclusion compounds with (cod)PtX2(X = Br or I). The formation of inclusion compounds is selective. α-CD did not form inclusion compounds with any transition-metal complexes with cycloocta-1,5-diene. Thermogravimetric measurements show that the complexes are stabilized by inclusion in cyclodextrin cavities. The inclusion compounds were characterized by1H-NMR, IR, UV, and circular dichroism spectra.

ISSN:0022-233X    

DOI:10.1080/00222338908051980

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Some inorganic polymers and their complexes with Rh or with Co-Ru were prepared. The catalytic behavior of these complexes for the hydroformylation of heptene-1 was studied. It was found that almost all of the rhodium complexes cannot tolerate higher reaction temperature when higher selectivity is wanted, except for the polyalumazane-Rh complex. But the cobalt and ruthenium bimetallic complex of polyalumazane can catalyze the hydroformylation of heptene-1 at higher temperature without any decrease in catalytic activity and with a selectivity of about 70% for branched aldehyde. Other factors affecting conversion and selectivity were also studied in detail.

ISSN:0022-233X    

DOI:10.1080/00222338908051981

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The immobilization of Br4MoO−in both poly-p-vinyipyridine with a flexible backbone and silica as a rigid polymer support was carried out. The oxidation of alcohols byt-butyl hydroperoxide (t-BuOOH) was then studied in the presence of the polymer-supported complexes obtained. The differences of the reactivity between catalysts supported by organic and inorganic polymers are discussed. The best carrier for Br4MoO−as an oxidation catalyst is a silica modified with silane coupling reagent (dimethyloctadecyl-[3-(trimethoxysilyl)propyl] ammonium chloride).

ISSN:0022-233X    

DOI:10.1080/00222338908051982

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The IR spectra of neodymium complexes supported on styrene-acrylic acid copolymer were investigated. The complexes possess a bidentate carboxylate structure, and the Nd‒O bond in the complexes is highly covalent. The effect of the nature and constitution of the supported neodymium complexes on their activity in butadiene polymerization was studied. The copolymer was prepared in THF or dioxane was better for the synthesis of highly active supported complexes. Polymer-supported neodymium complexes containing about 12 wt% of -COOH gave optimum catalytic activity at a Nd/‒COOH mole ratio of 0.20.

ISSN:0022-233X    

DOI:10.1080/00222338908051983

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

A series of polymer-anchored Rh-Co heteronuclear carbonyl cluster catalysts was synthesized by the reaction of Co2Rh2(CO)12with various kinds of polymer supports, such as poly(2-vinylpyridine), poly(N-vinyl-2-pyrrolidone), poly(styrene-co-maleic anhydride), and aminated products of the latter. The structure of the catalysts was characterized by IR, SEM, XPS, and ICP. The influence of the support structure and crosslinking, the metal content, and the type of substrate on the catalyst's hydroformylation properties was studied. The stability of the catalysts was examined by IR. The experimental results indicate that the supported cluster catalysts possess high catalytic activity, better selectivity, good stability, and reproducibility.

ISSN:0022-233X    

DOI:10.1080/00222338908051984

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Recent years have seen substantial progress in our understanding of biological electron-transfer mechanisms. Of particular value have been soluble c-type cytochromes, due to the large structural base available. Using structurally homologous families of simple redox proteins, the contribution of driving force, electrostatics, and sterics to the kinetics of electron transfer has been quantified. Importantly, because Marcus' theory for outer-sphere electron transfer is applicable, we have been able to develop an approach termed “kinetic taxonomy.” That is, based on the correlations obtained with a large number of redox proteins in different structural families, we can predict structural features from the kinetic properties of redox proteins of unknown structure. More recently, we have been able to establish a role for dynamics, orientation, and intervening media in intracomplex electron transfer when two redox proteins form a long-lived complex.

ISSN:0022-233X    

DOI:10.1080/00222338908051985

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor