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Synthesis, characterization and reactivity of tetracyclopentadienyl derivatives of niobium(IV)
No full textSynthesis and characterization of mono and bimetallic derivatives of Groups 4 and 5 with 2,5dimethoxy1,4benzoquinone
No full textThe ligating properties of 2,5-dimethoxy-1,4-benzoquinone, C8H8O4 1 towards metallic Lewis acids and organometallics
in low oxidation states has been investigated. The title compound reacts with Group 4 tetrahalides to give adducts of
formula MCl4(C8H8O4) (M = Ti 4a; M = Zr 4b) and (TiCl4)2(C8H8O4) 5. Moreover, bis-cyclopentadienyl derivatives of
titanium() (TiCp2L2; L = CO, PMe3) and vanadium() (VCp2) react with 1 affording both 1 : 1 and 2 : 1 derivatives
of general formula MCp2(C8H8O4) (M = Ti 10; M = V 7), (MCp2)2(C8H8O4) (M = Ti 11; M = V 6). The molecular
structure of 6 has been determined by X-ray diffraction showing the presence of bimetallic units, with two [VCp2]
fragments bonded to a quinonoid oxygen atom of a bridging 2,5-dimethoxy-1,4-benzenedialcoholato. The derivatives
[(MCp2)2(C8H8O4)][BPh4]n (M = Ti, V; n = 1 12a, b; n = 2 12c, d) have been prepared by oxidation of (MCp2)2(C8H8O4)
(M = Ti 11; M = V 6) with a stoichiometric amount of [FeCp2][BPh4]. The reaction of the vanadium derivative
VCp2(C8H8O4) 7 with TiCl4 affords the heterobimetallic compound VCp2(C8H8O4)TiCl4 8. The magnetic properties
of the 1 : 1 and 2 : 1 species are reported
Tetra-, penta-, and hexacoordination in iron (II) adducts of aliphatic bidentate amines : Crystal and molecular structure of the mononuclear complexes Fe(dienMe)Cl2 and Fe(tmeda)I2 ; Dedicated to Professor René Poilblanc in recognition of his outstanding scientific contributions. dienMe = bis(2-dimethyl-aminoethyl)methylamine; tmeda = N,N,N′,N′-tetramethylethylenediamine
No full textThe thf adduct of FeCl2, FeCl2(thf)1.5, reacts with bidentate aliphatic nitrogen bases in toluene as medium to give the corresponding adducts of FeCl2. X-ray crystallography of Fe(dienMe)Cl2 (dienMe = bis(2-dimethylaminoethyl)methylamine) has shown the compound to be mononuclear with pentacoordinated iron, thus confirming an earlier suggestion by Ciampolini and Speroni based on spectroscopic and magnetic data. Crystal data: C9H23Cl2FeN3; M = 300.06 g mol-1; monoclinic; space group P21/c (No.14); a = 8.396(3); b = 29.556(8); c = 12.108(3) Å ; g= 101.22(4)° ; V = 2947(3) Å 3; Z = 8; dcalc = 1.352 g.cm-3; lAg-Ka = 0.56087 Å ; mu = 7.02 cm-1; F(000) = 1264; T = 293 K. Bromo- and iodo complexes of iron(II) have been prepared by using cis-FeX2(CO)4 (X = Br, I) as precursors. The reaction of cis-Fe(CO)4X2 (X = Br, I) with N,N’-dimethylethylenediamine (dmeda) or N,N,N’,N’-tetramethylethylenediamine (tmeda) in heptane as medium affords adducts of general formula Fe(NN)nX2 - X = Br, I; NN = dmeda, n = 2, NN = tmeda, n = 1. The iodo derivative Fe(tmeda)I2 has been characterized by X-ray crystallography and found to be mononuclear with tetracoordinated iron(II) in a distorted tetrahedral arrangement of two iodo- and two nitrogen atoms of the bidentate amine. Crystal data: C6H16FeI2N2; M = 425.86 gmol-1; orthorhombic; space group Pbca (No. 61); a = 14.724(2); b = 15.151(4); c = 24.173(3) Å ; U = 5392(2) Å 3; Z = 16; dcalc = 2.098 g cm-3; Ag-Ka = 0.56087 Å ; mu = 29.52 cm-1; F(000) = 3168; T = 293 K
Niobium(I) and tantalum(I) tetracarbonyl derivatives containing nitrogen ligands
No full textDiamino derivatives of niobium(l) and tantalum(l) of general formula MX(CO)4(NN), MNb, Ta; XCl, 1; NNethylendiamine
(en), N,N%dimethylethylendiamine (dmen), N,N,N%,N%-tetramethylethylendiamine (tmen), 2,2-dipyridyl (2,2%-dipy), 4,4%-
dipyridyl (4,4%-dipy), have been prepared by oxidation of the [M(CO)6] anions with either 1,1%-dimethyl-4,4%-dipyridilium
diiodide (methylviologen, mvI2) in the presence of the diamine or the diprotonated salt of the corresponding diamine,
[(NN)H2]Cl2. Alternatively, these derivatives have been obtained by amine exchange reactions on [MCl(CO)4(4,4-dipy)]n or by
chloride substitution on the dinuclear anion [Nb2(m-Cl)3(CO)8]. The MX(CO)4(NN) derivatives have been characterized by
analytical, spectroscopic and, in the case of TaI(CO)4 (tmen), also by single crystal diffractometry. Crystal data. TaI(CO)4(tmen),
monoclinic, space group P21:c (No. 14); a16.222 (5); b12.855 (3); c16.452 (6) A°
, b117.67 (2)°, M536.10 g mol1;
V3038.4 (1) A°
3; Z8; Dc2.344 g cm3; l0.7107 A°
; T203 K; m91.71 cm1; F(000)1984; R0.045; Rw0.048
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
N-substituted bis(diphenylphosphanyl)amine ligands bearing the thioether functional group: coordination modes in PtCo2 and PtMo2 based clusters
No full textVariations on the Author
Full text link“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
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