121,861 research outputs found
Functionalised and cyclometallated N-Heterocyclic Carbene complexes of Pd, Ni, Rh and Ir : synthesis and applications
No full textNew imidazolinium salts have been synthesised with the following substitution: (i) 2-(3-methylpyridyl), 2-pyridyl; (ii) alkoxyphenyl (o-OMe-phenyl, p-OMe-phenyl, o,p-(OMe)2-phenyl, o,p,o-(OMe)3-phenyl, o-OiPr-phenyl, p-OiPr-phenyl); (iii) substituted aryl (o-Et-phenyl, o-iPr-phenyl); (iv) fluoraryl (m, m-(CF3)2-phenyl, o-F-phenyl, o,p-F2-phenyl). In addition, novel pyridyl functionalised imidazolium salts have been synthesised. The targeted imidazol(in)ium salts were hoped to give rise to metal complexes with hemilabile coordination sites (pyridine functionalised species) or to cyclometallated complexes which on heating may generate active catalysts. Deprotonation of two of the imidazolium salts led to the isolation of the corresponding free carbenes. Five novel pyridyl functionalised imidazoline-2-ylidene complexes of palladium, three novel imidazolin-2-ylidene palladacycle complexes, four novel aryl substituted imidazoline-2-ylidene palladium complexes and two novel alkoxyphenyl imidazolin-2-ylidene palladacycle complexes have been synthesised by reacting the in situ deprotonated salt with various palladium precursors or by transmetallation reactions from silver carbine complexes. The complexes were characterised by analytical, spectroscopic and diffraction techniques. Interestingly, the first palladium ‘C-C-C pincer’ type complex (3.14) has been isolated after facile double cyclometallation succeeding the ligand complexation. Selected palladium imidazoline-2-ylidene complexes have been tested as catalysts for Heck coupling reactions. [1,3-Bis(4-methoxyphenyl)imidazolin-2-ylidene] {2-[3-(4-methoxyphenyl) imidazolin-2-ylidene] -5- methoxy phenyl-κ2C,C’} methyl palladium(II) (3.16) and [1,3-bis(2,4-dimethoxyphenyl)imidazolin-2-ylidene] { 2-[3-(2,4-dimethoxy phenyl) imidazolin-2-ylidene] -3,5- dimethoxy phenyl- κ2C,C’} methyl palladium(II) (3.15) have been found to be excellent catalysts for the Heck couplings of aryl bromides, deactivated aryl bromides and activated aryl chlorides, while moderate results for the Heck coupling of chlorobenzene have been achieved. These complexes surpass the activity of standard palladium phosphine complexes and are amongst the most active palladium NHC complexes reported to date. Five novel picolyl-functionalised imidazol-2-ylidene complexes of Rh(I) and Ir(I) have been prepared and characterised by the reaction of [M(COD)C1]2 (M = Rh, Ir) with 1-[2-(3-methyl)pyridyl]3-[2,6-diisopropyl)phenyl]imidazol-2-ylidene (2.1b). When M = Rh the nature of the products was found to be dependent on the reactant ratio. Furthermore, one novel Ir(III) picolyl functionalised imidazolin-2-ylidene complex featuring a 1-κ-4,5,6-η-C8H12 moiety (5,6) has been synthesised by reacting [Ir(COD)C1]2 with, in situ formed, 1-[2-(3-picolyl)]-3- (2,6-diisopropylphenyl) imidazolin-2-ylidene.</p
(1)Pyridine and phosphine functionalised N-heterocyclic carbene complexes of rhodium and iridium
No full textThe pyridine functionalised N-heterocyclic carbene complexes [M(kappa(2)-NCDIPP)(COD)](+)A(-), NCDIPP = 3-(2, 6-(Pr2C6H3)-C-i)-1-[2-(3-picolyl)]-imidazol-2-ylideni, A(-) = [(Ar4B)-B-F](-), [{3,5-(CF3)(2)C6H2}(4)B](-), M = Rh, 1b, Ir, 4, have been prepared in two steps by reaction of the [M(COD)Cl](2) with the isolated NCDIPP to [Rh(kappa(1)-NCDIPP)(COD)Cl], 2, and [Ir(kappa(2)-NCDIPP)(COD)Cl], 3, followed by anion exchange with Na(+)A(-). The phosphine functionalised N-heterocyclic carbene complex [Rh(PCH2Cmes)(2)]Br, 6, PCH2Cmes = 1-(diphenylphosphino-methyl)-3-(2,4,6-Me3C6H2)-imidazol-2-ylidene, was prepared by the reaction of the [Rh(COD)Cl](2) with the corresponding N-heterocyclic carbene generated in situ. Monomeric [Rh(PCH2CH2CDIPP)(acac)], 7 was prepared by an analogous reactions from [Rh(COE)(2)(acac)]. In contrast, phosphine functionalised N-heterocyclic carbene complexes of iridium (I) were not easily accessible. However, the reaction of [Ir(COD)(mu-Cl)2(mu-H)]2 with PCH2CH2Cmes gave complex [Ir(COD)(PCH2CH2Cmes.)Br], 8, in which the carbene is coordinated to the metal in an 'abnormal' mode
Cyclometalated and alkoxyphenyl-substituted palladium imidazolin-2-ylidene complexes: synthetic, structural, and catalytic studies
No full textSome new N,N'-bis(aryl)imidazolinium salts (3a-h), in which the N-aryl groups have one unsubstituted ortho position and alkyl (Me, Pri) or alkoxy (OMe, OPri) substitution at the other ortho and/or para positions, have been prepared. They were used for the synthesis of N-heterocyclic carbene complexes of palladium in which the N-heterocyclic carbene is attached to cyclometalated or electron-rich aromatic rings (4, 5, 11d,e). The reaction of Pd(tmed)(CH3)2 with the N-heterocyclic carbene generated from 3b and base gave the dimethyl complex 6, which quantitatively eliminated ethane to form the Pd(0) complex 7. The latter was converted to a new type of "pincer" complex (8) by facile cyclometalation of both aromatic groups of the N-heterocyclic carbene ligand. The activities of the new complexes 4 and 9d,e in the Heck reaction of aryl halides were compared. At higher temperatures the complexes 9d,e show low activity in the coupling of aryl chlorides. <br/
Picoline and pyridine functionalised chelate N-heterocyclic carbene complexes of nickel: synthesis and structural studies
No full textThe first pyridine and picoline functionalised N-heterocyclic carbene complexes of nickel are described in this paper. The nature of the isolated complexes is critically dependent on the bite angle and the substituents of the ligand used and the synthetic method for the introduction of the ligand on the metal. From NiBr2 (DME), DME=1,2-dimethoxyethane, by transmetallation with one equivalent of Ag(CN)2]Br2 (3). Transmetallation with Ag(C-N)Cl, (C-N) = [3-(2,6-Pr-2(i) C6H3)1[1-(2-pyridyl)imidazol-2-ylidene] afforded the bimetallic species [(C-N)(2)Ni(mu-Br)(2) NiBr2] (4), containing one octahedral and one tetrahedral nickel centre. Finally, from the reaction of NiBr2 (DME) with free (C-N*), (C-N*) = 3-(2,6-(Pr2C6H3)-C-i)-1-[2-(3-picolyl)]-imidazol-2-ylidene, good yields of Ni(C-N*)Br-2, (6) were obtained. Attempts to alkylate (1) were not successful
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
The vanishing author in computer-generated works: a critical analysis of recent Australian case law
No full textAbstract
The use of software is ubiquitous in the creation of many copyright works, yet the requirement in copyright law that every work have a human author who engages in independent intellectual effort means that its use may prevent copyright subsistence. Several recent Australian cases have refocused attention on authorship as an essential criterion of copyright subsistence, and these cases suggest that much computer-produced output may be authorless and thus lack copyright protection. This article, the first in a two-part series, analyses how each case deals with the question of authorship of computer-produced works and why the use of software diminishes copyright protection for a significant number of computer-generated works. The article critiques the application of conventional notions of human authorship developed in the pre-computer age to modern productions and suggests alternative approaches to authorship that satisfy both the major objectives of copyright policy and the need to adapt to the computer age. The article argues that, without a broader judicial approach to authorship of computer-generated works, Parliament must remedy the lacuna in protection for these ‘authorless’ works. Possible solutions for reform are suggested. In a forthcoming article, the author comprehensively examines those reform proposals
Diffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Dissipative Range Scaling of Higher Order Structure Functions for Velocity and Passive Scalars
No full textDifferently to Kolmogorov's second similarity hypothesis, we find that the 2n-th order velocity and scalar structure functions scale with n-th order moment of the energy dissipation and the scalar dissipation, respectively. The origins of this scaling are analyzed by the transport equations of the fourth order velocity and scalar increment moments and by direct numerical simulations
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