Transition Metal Reagents Research Articles

ChemInform Abstract: Transition Metal Promoted Reactions of Polyhedral Boranes and Carboranes

The use of transition—metal catalysts has revolutionalized the synthetic strategies of organic chemistry; however, it has been only recently that these reagents have been applied in the inorganic area. Our work is described which has demonstrated that such reagents can be used to catalyze or promote a variety of transformations involving polyhedral boranes and carboranes, including: borane—acetylene addition, acetylene—borane insertion, borane—olefin coupling, dehydrocoupling, dehydrocondensation and cage—growth reactions. Selected examples which illustrate the scope and possible mechanisms of these reactions are discussed. INTRODUCTION One of the major problems in polyhedral boron cage chemistry has been the lack of general synthetic routes for the construction of larger cage systems. This limitation has both hampered the potential commercial applications of these types of compounds and seriously retarded further exploratory research in the area. Our work is attempting to address this problem by examining the use of transition metal reagents, similar to those widely employed in organic and organometallic chemistry, to induce high yield, selective transformations in polyhedral boranes and carboranes. Transition—metal reagents are widely used in organic chemistry to catalyze or promote a variety of transformations which may have parallels in polyhedral borane chemistry. Some reaction types and examples of possible applications are summarized in the following table: Metal Promoted Reactions Organic Polyhedral Boranes 1. Acetylene Addition Synthesis of Olefins, Synthesis of Alkenyl— Hydrosilylation boranes and —Carboranes 2. Olefin Substitution Arene—Olefin Coupling, Synthesis of Alkenyl— Synthesis of Substituted boranes and —Carboranes Olef ins 3. Cyclo—Addition Synthesis of Alicyclic Synthesis of Two—, Four— Compounds or Higher Carbon Carbor— ane Cages 4. Dehydrocoupling Arene—Coupling Synthesis of Multi—Cage Compounds 5. Dehydrogenations Synthesis of Unsaturated Cage Closure Reactions; Organics Generation of Reactive Fragements It should be noted, however, that while there may indeed be close analogies between metal—promoted organic and boron hydride reactions, there are also significant differences. For example, a typical C—H bond energy is substantially greater than that for an analogous B—H bond. This difference generally means that metal—catalyzed reactions involving boron hydrides occur under much milder conditions than the analogous organic systems. Likewise, polyhedral boranes are both more reactive (particularly toward basic ligands) and have sites of different reactivity in the same molecule, leading to more complex (and as a result more intriguing) reaction mechanisms and selectivities. As a result of our work we have now developed six separate classes of transition metal promoted polyhedral borane reactions which are described, with selected examples, in the following sections. 837 Catalyst B5H9 + RCCR' OC PPh z1IIIEI7 Ph3P Ci Ph3P

Transition-metal-promoted reactions of boron hydrides. 10. Rhodium-catalyzed syntheses of B-alkenylborazines

The authors previously shown that transition-metal reagents can be used to activate the B-H bonds in a variety of polyhedral boranes and carboranes and that this activation can induce numerous important synthetic transitions. They have now initiated studies of the application of transition-metal catalysts to promote the reactions of boron nitrogen ring compounds and report here the development of a metal-catalyzed, high yield route of B-alkenylborazines.

Synthesis of heterometallic carbide clusters containing three iron atoms: [PPN]2[MFe3(CO)13C] (M = Cr, W), [PPN]2[Cr2Fe3(CO)16C], Rh2Fe3(CO)14C, and [PPN][Rh3Fe3(CO)15C

Redox-condensation reactions involving (PPN)/sub 2/(Fe/sub 3/(CO)/sub 9/(CCO)) and electrophilic transition-metal reagents lead to (PPN)/sub 2/(MFe/sub 3/(CO)/sub 13/C) (M = Cr, W), (PPN)/sub 2/(Cr/sub 2/Fe/sub 3/(CO)/sub 16/C), Rh/sub 2/Fe/sub 3/(CO)/sub 14/C, and (PPN)(Rh/sub 3/Fe/sub 3/(CO)/sub 15/C). Variable-temperature /sup 13/C NMR spectroscopy was employed to assign the structures of the tetranuclear clusters and Rh/sub 2/Fe/sup 3/(CO)/sub 14/C in solution. An improved synthesis of (PPN)(RhFe/sub 3/(CO)/sub 12/C) and more complete variable-temperature (ca. -130 to +20 /sup 0/C) /sup 13/C NMR spectra of this cluster and (PPN)(MnFe/sub 3/(CO)/sub 13/C) are discussed. All of the tetranuclear clusters are assigned butterfly metal geometries will the heterometals located at hinge sites. Attempts to prepare iron-molybdenum carbide clusters are discussed. The structure of (PPN)(Rh/sub 3/Fe/sub 3/(CO)/sub 15/C) was determined by a single-crystal x-ray diffraction study and was found to consist of a trigonal-antiprismatic metal array with the carbide ligand within the metal polyhedron. The iron atoms define one of the trigonal faces and the rhodium atoms define the other. Crystal data for (PPN)(Rh/sub 3/Fe/sub 3/(CO)/sub 15/C): monoclinic, space group P2/sub 1//n, a = 16.220 (6) A, b = 9.282 (3) A, c = 35.17 (3) A, ..beta.. = 94.84 (5)/sup 0/, Z = 4. 28 references, 5 figures,more » 6 tables.« less

A transition-metal chromophore as a new, sensitive spectroscopic tag for proteins. Selective covalent labeling of histidine residues in cytochromes c with chloro(2,2':6'2"-terpyridine)platinum(II) chloride

Reactivity and selectivity of Pt(trpy)Cl/sup +/ toward proteins are studied with cytochromes c from horse and tuna as examples. The new transition-metal reagent is specific for histidine residues at pH 5. The reaction, facile one-step displacement of the Cl/sup -/ ligand by imidazole, produces good yield. The binding sites, His 26 and His 33 in the horse protein and His 26 in the tuna protein, are identified by UV-vis spectrophotometry and by peptide-mapping experiments. Model complexes with imidazole, histidine, histidine derivatives, and histidine-containing peptides are prepared and characterized. The covalently attached Pt(trpy)/sup 2 +/ labels allow easy separation of the protein derivatives by cation-exchange chromatography. The labels do not perturb the conformation and reduction potential of cytochrome c, as shown by UV-vis spectrophotometry, cyclic voltammetry, differential-pulse voltammetry, EPR spectroscopy, and /sup 1/H NMR spectroscopy. The selectivity of Pt(trpy)Cl/sup +/ is entirely opposite from that of PtCl/sub 4//sup 2 -/ although both of them are platinum(II)-chloro complexes. Owing to an interplay between the steric and electronic effects of the terpyridyl ligand, the new reagent is unreactive toward methionine (a thio ether) and cystine (a disulfide), which are otherwise highly nucleophilic ligands, but very reactive toward imidazole, which is otherwise a relativelymore » weak ligand. Unusual and useful selectivity of preformed transition-metal complexes toward proteins evidently can be achieved by a judicious choice of ancillary ligands.« less

Transition metal promoted reactions of polyhedral boranes and carboranes

Abstract

ChemInform Abstract: CHARACTERISTICS IN THE REACTIONS OF ALLYLSILANES AND APPLICATIONS TO ORGANIC SYNTHESIS

Allylsilanes can provide synthetic strategies which are not achieved with other allylic metal reagents such as the Grignard, lithium and transition metal reagents. In this review article, the characteristics in the reactions of allylsilanes, especially not only enhanced reactivities towards various electrophiles due to σ-π conjugation but also regio-, stereo-, and chemoselectivities, are surveyed. Moreover, a variety of allylsilanes that have been synthesized and utilized as versatile synthetic equivalents are summarized.

アリルシランの反応の特徴と有機合成への応用

Allylsilanes can provide synthetic strategies which are not achieved with other allylic metal reagents such as the Grignard, lithium and transition metal reagents. In this review article, the characteristics in the reactions of allylsilanes, especially not only enhanced reactivities towards various electrophiles due to σ-π conjugation but also regio-, stereo-, and chemoselectivities, are surveyed. Moreover, a variety of allylsilanes that have been synthesized and utilized as versatile synthetic equivalents are summarized.

ChemInform Abstract: NEW SYNTHETIC METHODS. 16. HYDROZIRCONATION‐ ORGANIC SYNTHESES WITH A NEW TRANSITION METAL REAGENT

Chemischer InformationsdienstVolume 7, Issue 39 Organoelement Compounds ChemInform Abstract: NEW SYNTHETIC METHODS. 16. HYDROZIRCONATION- ORGANIC SYNTHESES WITH A NEW TRANSITION METAL REAGENT JEFFREY SCHWARTZ, JEFFREY SCHWARTZSearch for more papers by this authorJAY A. LABINGER, JAY A. LABINGERSearch for more papers by this author JEFFREY SCHWARTZ, JEFFREY SCHWARTZSearch for more papers by this authorJAY A. LABINGER, JAY A. LABINGERSearch for more papers by this author First published: September 28, 1976 https://doi.org/10.1002/chin.197639302Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume7, Issue39September 28, 1976 RelatedInformation

Hydrozirconation: A New Transition Metal Reagent for Organic Synthesis

AbstractHydrozirconation has recently been developed as a procedure for functionalizing alkenes, alkynes, and 1,3‐dienes via organozirconium(IV) intermediates. These intermediates react with a variety of electrophilic reagents to give organic products in high yield. Mechanisms of reactions involved in these sequences are discussed.

ChemInform Abstract: BRIDGE INSERTION REACTIONS OF THE 2,3‐C2B4H7‐ION WITH ALUMINIUM, GALLIUM AND TRANSITION METAL REAGENTS

Chemischer InformationsdienstVolume 6, Issue 22 Organoelement Compounds ChemInform Abstract: BRIDGE INSERTION REACTIONS OF THE 2,3-C2B4H7-ION WITH ALUMINIUM, GALLIUM AND TRANSITION METAL REAGENTS C. P. MAGEE, C. P. MAGEESearch for more papers by this authorL. G. SNEDDON, L. G. SNEDDONSearch for more papers by this authorD. C. BEER, D. C. BEERSearch for more papers by this authorR. N. GRIMES, R. N. GRIMESSearch for more papers by this author C. P. MAGEE, C. P. MAGEESearch for more papers by this authorL. G. SNEDDON, L. G. SNEDDONSearch for more papers by this authorD. C. BEER, D. C. BEERSearch for more papers by this authorR. N. GRIMES, R. N. GRIMESSearch for more papers by this author First published: June 3, 1975 https://doi.org/10.1002/chin.197522376AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume6, Issue22June 3, 1975 RelatedInformation

Bridge insertion reactions of the 2,3-C 2B 4H 7− ion with aluminum, gallium, and transition metal reagents

The reaction of lithium or sodium salts of the 2,3-C 2B 4H 7 − anion with organometallic reagents of aluminum, gallium, rhodium, gold and mercury effects insertion of the metal atom into a bridging position on the base of the pyramidal carborane cage, with the metal apparently linked to the cage by a BMB three-center, two-electron bond. μ-Dimethylaluminum-2,3- nido-dicarbahexaborane(8) is extremely unstable in solution or in the liquid phase with respect to decomposition to 2,3-C 2B 4H 8, but in the gas phase forms CH 3AlC 2B 4H 6. The gallium-bridged analog is thermally stable but reacts readily with HCl to generate C 2B 4H 8 and (CH 3) 2GaCl; however, under no conditions studied did this material rearrange to the previously characterized closo-gallacarborane, 1-CH 3-1,2,3-GaC 2B 4H 6. The compounds μ-[(C 6H 5) 3P] 3RhC 2B 4H 7 and μ-[(C 6H 5) 3P]AuC 2B 4H 7 were prepared and characterized as moderately air-sensitive crystalline solids, and a partially characterized, unstable material believed to be μ-C 6H 5HgC 2B 4H 7 was obtained.

Metallation of azobenzenes by fluorine-abstraction: structure of a ruthenium complex containing nonafluoro(phenylazo)phenyl-2C,N′ and diphenyl-2-(η-cyclopentadienylphenyl)phosphine groups

The formation of metallated azobenzene derivatives by fluorine-abstraction reactions using nucleophilic transition metal reagents has been achieved; the structure of an ortho-metallated complex, derived from decafluoroazobenzene and also containing a Ph2P(C6H4C5H4) ligand is described.

Selective cleavage of allyl ethers under mild conditions by transition metal reagents

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSelective cleavage of allyl ethers under mild conditions by transition metal reagentsE. J. Corey and J. William SuggsCite this: J. Org. Chem. 1973, 38, 18, 3224Publication Date (Print):September 1, 1973Publication History Published online1 May 2002Published inissue 1 September 1973https://doi.org/10.1021/jo00958a032RIGHTS & PERMISSIONSArticle Views2411Altmetric-Citations321LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (135 KB) Get e-Alerts Get e-Alerts