1,720,958 research outputs found
o-(Cyclohexyliminoethyl)(arylamido)benzene and related complexes of zirconium and titanium. The non-innocence of the ketimino functionality
No full textN-Arylamido complexes of zirconium in which the amido functional group is attached to an o-(alkyliminoethyl) substituted aromatic ring, have been synthesised by salt elimination reactions and characterised by spectroscopic and diffraction methods; they are analogous to the N-silylamido species recently reported (Dalton Trans., 2002, 3290-3299). The ligands2-[CyN=C(CH3)]C6H4N(H)(xyl), (LH)-H-xyl, and 2-[CyN=C(CH3)] C6H4N(H)(mes) (LH)-H-mes, Cy = C6H11, xyl = 3,5-Me2C6H3 mes = 2,4,6-Me3C6H2, were prepared in good yields by Buchwald-Hartwig amination of the arylbromides with 2-[CyN=C(CH3)]C6H4NH2. Reaction of (LLi)-Li-mes with Zr(NEt2)(2)Cl-2(thf)(2) gave after chloride substitution the arylamido ketimino complex (LZr)-Zr-mes(NEt2)(2)Cl 1; variable amounts of the arylamido vinylamido complex 2 were also obtained. Interaction of (LLi)-Li-mes or (LLi)-Li-xyl with Ti(NMe2)(2)Cl-2 gave rise to the tripodal bis-amido amino complexes 5 and 6 possibly formed by ligand rearrangement involving migration of the dimethylamido group to the ketimino carbon
Dimethylxanthene- and dibenzofuran-diamido complexes of titanium
No full textThe new ligands 4,5-dialkyl-and-diaryl-amido-9,9-dimethylxanthene and 4,6-dialkyl-and-diaryl-amido dibenzofuran serve as rigid,
pre-organised and tunable spectators for group 4 metals. The structure of a titanium complex with 4,5-di-cyclohexylamido-9,9-
dimethylxanthene is reported
Titanium(IV) and zirconium(IV) amido complexes derived from the azaoxa macrocycle 3,3-dimethyl-1,5-diaza-8-oxacyclodecane
No full textThe novel tridentate azaoxa macrocycle [O(NH)(2)], 3,3-dimethyl-1,5-diaza-8-oxacyclodecane, can be singly or doubly lithiated with (BuLi)-Bu-n at the secondary amine N atoms, giving [O(NH)N]Li and [O(N)(2)]Li-2, respectively, and further elaborated with introduction of TMS substituents via reaction with (TMS) Cl. Aminolysis of [Ti(NMe2)(2)Cl-2] or [Zr(NR2)(2)Cl-2(THF)(2)] with [O(NH)(2)] in toluene gave the distorted octahedral M[O(NH) N](NR2) Cl-2 (M) Ti, R) Me; M) Zr, R) Me or Et), in which the macrocycle functions as a monoanionic ligand via an amido, an amine, and an ether functionality. Salt metathesis of [Zr(NEt2)(2)Cl-2(THF)(2)] with [O(NH)N] Li in toluene afforded Zr[(O(NH) N)](NEt2)(2)Cl, the structure of which also confirms tridentate macrocycle coordination via one amido, one amine, and one ether group; in contrast, analogous salt metathesis involving [Zr(NEt2)(2)Cl-2(THF)(2)] and [O(N)(2)Li-2] gave the "sandwich" complex [(ON2)(2)Zr], with the macrocycle behaving as a dianionic ligand (Porter, R. M.; et al. Dalton Trans. 2005, 427). Finally, treatment of [O(NH)(2)] with AlMe3 gave the simple donor-acceptor adduct [O(NH)(2)]AlMe3, which resisted alkanolysis by prolonged heating. In the presence of MAO the new zirconium, titanium, and aluminum complexes show low activity in the polymerization of ethylene
Diamido tantalum(V) complexes derived from a diazamacrocycle
No full textThe amido complexes [Ta{O(N)2}(CH2Ph)3], (1), [Ta{O(N)2}(μ-CHBut){μ-O(NH)N}Li], (2), and [Ta{O(N)2}Cl3], (3), all featuring the dianionic diamido macrocycle [O(N)2]2− originating from O(NH)2 by deprotonation, O(NH)2 = 3,3-dimethyl-1,5-diaza-8-oxacyclodecane, have been prepared from Ta(CH2Ph)5, Ta(CH2 tBu)3Cl2 and TaCl5 by alkanolysis, salt metathesis with Li2[O(N)2] and Me3SiCl elimination with O(NSiMe3)2, respectively. Structural analyses revealed that in (1) the macrocycle is facially coordinated, while (2) contains one dianionic, facially coordinated macrocycle and one monoanionic macrocycle coordinating one lithium atom and metallated at one of the 3-methyl groups by the Ta.</p
Zirconium and titanium amido complexes with 3,3-dimethyl-1,5-diaza-8-oxacyclodecane; facile C-H activation of the macrocyclic rim
No full textReaction of the dilithium salt of 3,3-dimethyl-1,5-diaza-8- oxacyclodecane, [(NLi)(2)O], with Zr(NEt)(2)Cl-2(thf)(2) gave the formally 20e(-) complex [Zr(N2O)(2)]; metallation of the macrocycle [(NH)(2)O], with Ti(benzyl)(4) gave rise to [(N2O)* Ti(benzyl)](2) in which the trianionic diamido (N2O)* was formed by an unprecedented C-H activation of the carbon a to the amido nitrogen
(Alkyliminomethyl)phenylamido and related complexes of zirconium and titanium
No full textA range of trialkylsilylamido complexes of zirconium in which the silylamido functional group is attached to an o-(alkyliminomethyl)- or an o-(alkyliminoethyl)-substituted aromatic ring have been synthesised by salt elimination or aminolysis reactions and characterised by spectroscopic and diffraction methods. The monoanionic ligands (L), formally isoelectronic to the cyclopentadienyl ligand, can be introduced to zirconium by reaction of LLi with ZrCl4 under a variety of conditions giving rise to complexes of type LZrCl3 and L2ZrCl2, by reaction of LLi with Zr(NMe2)(2)Cl-2 (THF)(2), and Zr(NEt2)(2) Cl-2 (THF)(2) giving rise to LZrCl(NMe2)(2)Cl and LZrCl(NEt2)(2)Cl, respectively, or by reaction of LH with Zr(NMe2)(4) giving rise to LZr(NMe2)(3). LZr(NMe2)(2)Cl and LZr(NEt2)(2)Cl can be transformed to LZrCl3 by reaction with Me3SiCl, while LZr(NMe2)(3) on heating rearranges to dimeric imido complexes by elimination of amidosilanes. Aminolysis of Zr(NMe2)(2)Cl-2 (THF)(2) with LH results in a formal insertion of the imino C=N into the Zr-amido bond. The combination of enolisable imine and a bulky silyl amide gave rise to a new mixed donor ligand system comprising of one silylamido and one eneamido group. Finally aminolysis of Ti(NMe2)Cl-2 with LH resulted in the isolation of a C-3 symmetric triamido titanium complex
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
- …
