Search results for "Metallocene"
showing 10 items of 109 documents
Agglomerated non-porous silica nanoparticles as model carriers in polyethylene synthesis
2004
Abstract Non-porous submicron silica particles (250 and 500 nm) with high monodispersity were agglomerated to form spherical agglomerates via spray drying. As a binder, 25 nm sized monodisperse silica spheres were selected from a variety of colloidal systems including Levasil-type and Aerosil-type silica nanoparticles. The use of such binders led to an increase of the specific surface area of the agglomerated carriers. All materials were characterised by nitrogen sorption, mercury intrusion and scanning electron microscopy. The silica agglomerates, with highly defined geometrical and pore structural parameters, were employed as model carriers in the heterogeneous polymerization of ethylene …
Synthesis, electrochemical and theoretical studies of the Au(i)-Cu(i) heterometallic clusters bearing ferrocenyl groups
2009
Treatment of the polymeric alkynyl compounds (AuC2R)n (R = Fc, C6H4Fc; Fc = ferrocenyl) with the diphosphine PPh2C6H4PPh2 gave complexes (RC2Au)PPh2C6H4PPh2(AuC2R) (1, R = Fc; 2, R = C6H4Fc) with end-capped ferrocenyl groups. The reactions of 1 or 2 with Cu(NCMe)4PF6 result in formation of the heterotrimetallic aggregates [{Au3Cu2(C2R)6}Au3(PPh2C6H4PPh2)3](PF6)2 (3, R = Fc; 4, R = C6H4Fc), which consist of the alkynyl clusters [Au3Cu2(C2R)6]−“wrapped” by the cationic [Au3(PPh2C6H4PPh2)3]3+“belt”. The novel compounds were characterized by NMR spectroscopy and ESI-MS measurements. The solid state structure of 3 is reported. Electrochemical properties of the complexes 1–4 have been studied. Th…
Synthesis and study of cytotoxic activity of 1,2,4-trioxane- and egonol-derived hybrid molecules against Plasmodium falciparum and multidrug-resistan…
2014
Abstract Malaria and cancer cause the death of millions of people every year. To combat these two diseases, it is important that new pharmaceutically active compounds have the ability to overcome multidrug resistance in cancer and Plasmodium falciparum strains. In search of effective anti-cancer and anti-malaria hybrids that possess improved properties compared to their parent compounds, a series of novel 1,2,4-trioxane-based hybrids incorporating egonol and/or ferrocene fragments were synthesized and tested in vitro against P. falciparum strains, CCRF–CEM cells and the multidrug-resistant P-glycoprotein-over-expressing CEM/ADR5000 cells. The most active compounds against P. falciparum stra…
Ferrocenyl-Coupled N-Heterocyclic Carbene Complexes of Gold(I)
2016
Four gold(I) carbene complexes featuring 4-ferro-cenyl-substituted imidazol-2-ylidene ligands were investigated for antiproliferative and antivascular properties. They were active against a panel of seven cancer cell lines, including multidrug-resistant ones, with low micromolar or nanomolar IC50 (72 h) values, according to their lipophilicity and cellular uptake. The delocalized lipophilic cationic complexes 8 and 10 acted by increasing the reactive oxygen species in two ways: through a genuine ferrocene effect and by inhibiting the thioredoxin reductase. Both complexes gave rise to a reorganization of the F-actin cytoskeleton in endothelial and melanoma cells, associated with a G1 phase c…
Bis-ferrocene derivatives of bridged calix[4]arenes: syntheis, X-ray crystal structure and electrochemical properties
1991
The reaction of chlorocarbonylferrocene (2) with bridged calix[4]arene macrocyclic compounds, in which two opposite para-positions are connected by an additional aliphatic chain where n = 5 (1a) or n = 8 (1b) respectively, gave the corresponding new redox-active bis-ferrocene derivatives of bridged calix[4]arenes, 3a and 3b. An X-ray diffraction study of 3a shows that the caliz[4]arene has a cone conformation in which the two ferrocene substituents are located on the phenolic units connected to each other by the aliphatic chain bridge. Cyclic voltammetric and coulometric studies in dichloromethane reveal that 3a and 3b undergo reversible two electron oxidations at + 0.90 V (versus SCE), sug…
Complexes hétéronucléaires Cp2MM′(Cp)(CO)3 (M Nb, Ta; M′ Mo, W) avec groupes carbonyles pontants et semi-pontants: synthèse et comportement dynam…
1991
Abstract Heteronuclear structures Cp 2 MM′(Cp)(CO) 3 (M Nb, Ta; M′ Mo, W) are obtained by heating Cp 2 MH 3 (M Nb, Ta) with Cp 2 M′ 2 (CO) 6 (M′ Mo, W) or starting from Cp 2 M(CO)H and Cp 2 M′ 2 (CO) 4 . These heterobimetallic complexes show three CO coordination modes: terminal, semi-bridging and bridging. The two cyclopentadienyl groups of the Cp 2 M moiety are anisochronous owing to molecular rigidity; rotation barriers around the MM′ bond have been estimated and are greatest with tantalum derivatives.
Compensation of steric demand by cation–π interactions, cobaltocenium cations as guests in tetraurea calix[4]arene dimers
2003
The affinities of ferrocene (2) and the cobaltocenium cation (3+), which have roughly the same size and differ in their charge, towards the inner cavity of the dimeric capsule formed by tetraurea calix[4]arene (1) were studied in C2D4Cl2 solutions. While 3+, which occupies more than 75% of the internal volume of the dimer, is readily encapsulated this is not the case for 2. This is probably due to cation-pi interactions, which operate only between 3+ and the aromatic rings of the calix[4]arene dimer. We found that the affinity of the cobaltocenium cation is higher than that of the tropylium cation (4+) and is only 2-3 times less than that of the tetraethylammoniun cation (5+). From the vari…
Gold(I) Complexes of Ferrocenyl Polyphosphines: Aurophilic Gold Chloride Formation and Phosphine-Concerted Shuttling of a Dinuclear [ClAu···AuCl] Fra…
2016
International audience; A smart steric control of the metallocene backbone in bis- and poly(phosphino)ferrocene ligands favors intramolecular aurophilic interactions between [AuCl] fragments in polynuclear gold(I) complexes. We synthesized and characterized by multinuclear NMR and X-ray diffraction analysis mono-, di-, and polynuclear gold complexes of constrained ferrocenyl diphosphines, which bear either bulky tert-butyl groups or more flexible siloxane substituents at the cyclopentadienyl rings. The complexes meso-1,1'-bis-(diphenylphosphino)-3,3'-di-tert-butylferrocene (4-m), rac-1,1'-bis[bis-(5-methy1-2-furyl)phosphino]-3,3'-di-tert-butyfferrocene (5-r), and rac-1,1'-bis ( diphenylphos…
Reactivity of the ansa-Bridged Metallocene Dichlorides [X(η5-C5H4)2]MCl2 (X = SiMe2, CMe2; M = Mo, W) toward Metallophosphide Anions [PPh2M‘(CO)x]- (…
1997
Two kinds of ansa derivatives, [SiMe2(η5-C5H4)2]MCl2 and [CMe2(η5-C5H4)2]MCl2 (M = Mo, W), are reacted with metallophosphide anions [PPh2M‘(CO)x]- (M‘ = Cr, Mo, W, x = 5; M‘ = Fe, x = 4). The silicon-bridged derivatives give the bimetallic systems [SiMe2(η5-C5H4)(η5-C5H3PPh2M‘(CO)x)]M(H)(Cl), which result from a regioselective substitution at the 3-position on the cyclopentadienyl ligand. In contrast, with the CMe2-bridged compounds, the substitution reaction occurs at the metallic center, giving μ-phosphido bimetallic complexes [CMe2(η5-C5H4)2]M(Cl)(μ-PPh2)M‘(CO)x. The solid-state structure of the bimetallic complex [CMe2(η5-C5H4)2]W(Cl)(μ-PPh2)Fe(CO)4 (7d) is reported.
Zirconium, hafnium and yttrium complexes containing two linked amido— tetramethylcyclopentadienyl ligands: Synthesis, reactivity and molecular struct…
1998
Abstract Zirconium and hafnium complexes M(η5: η1−C5Me4SiMe2NR′)xCl(4−2x) (M = Zr, Hf; x = 1, 2; R′ = iPr, tBu) containing one or two linked amido-tetramethylcyclopentadienyl ligands C5Me4SiMe2NR′ have been synthesized by the reaction of the dilithium derivative Li2(C5Me4SiMe2NR′) with MCl4(THF)2. The crystal structure of the hafnium complex Hf(η5: η1−C5Me4SiMe2NiPr)2 has been determined by a single-crystal X-ray diffraction study and shows a C2-symmetric helical metallocene, in which the amido ligands are bonded as π-donor ligands with Hf—N bond lengths of 2.115(2) A. The isoelectronic heterobimetallic yttrium complex Li[Y(η5: η1−C5Me4SiMe2NCH2CH2OMe)2] reacts with phenylacetylene to give …