Search results for "Metallocene"
showing 10 items of 109 documents
Conformational Control of Metallocene Backbone by Cyclopentadienyl Ring Substitution: a New Concept in Polyphosphane Ligands Evidenced by “Through-Sp…
2009
The present study deals with the conformational control of the metallocene backbone within ferrocenyl polyphosphane ligands and their performance in the highly topical palladium-catalyzed heteroaromatics arylation by direct C−H activation. New substituted cyclopentadienyl rings were synthesized, which allowed the assembling of original tri- and diphosphanes. The bulky cyclopentadienyl lithium salts diphenylphosphino-3-(triphenyl)methylcyclopentadienyllithium (4) and 1,2-bis(diphenylphosphino)-4-(triphenyl)methylcyclopentadienyllithium (5) were prepared in excellent yield. The assembling of these new hindered cyclopentadienyl salts (Cp) with other Cp fragments was performed in order to prepa…
Long-range electronic connection in picket-fence like ferrocene–porphyrin derivatives
2012
The effects of a direct connection between ferrocene and porphyrin units have been thoroughly investigated by electrochemical and spectroscopic methods. These data not only reveal that substitution of the porphyrin macrocycle by one, two, three or four ferrocenyl groups strongly affects the electronic properties of the porphyrin and ferrocenyl moieties, they also clearly demonstrate that the metallocene centres are "connected" through the porphyrin-based electronic network. The dynamic properties of selected ferrocene-porphyrin conjugates have been investigated by VT NMR and metadynamic calculations. 1,3-Dithiolanyl protecting groups have been introduced on the upper rings of the ferrocene …
Effect of AlR3 (R = Me, Et, iBu) addition on the composition and microstructure of ethylene/1-olefin copolymers made with post-metallocene complexes …
2018
The effect of trialkylaluminum compound (AlR3, where R = Me, Et, iBu) addition on the performance of the [LigZrCl]2(μ-O)/AliBu3/Ph3CB(C6F5)4 and LigTiCl2/AliBu3/Ph3CB(C6F5)4 (Lig = Me2N(CH2)2N(CH2-2-O-3,5-tBu2-C6H2)2) catalysts in ethylene/1-olefin copolymerization was investigated. The presence of AlMe3 in the feed during the copolymerization process catalyzed by the diamine-bis(phenolate) zirconium catalyst greatly increases the amount of incorporated comonomer and leads to microstructural changes, e.g., the formation of blocky and alternating sequences of 1-olefin units. Moreover, the use of AlMe3 limits the reaction yield and decreases the molecular weight of the produced copolymers. Th…
The synthesis of metallocene-labelled drugs for biological assays
1990
Several drugs (amphetamine, desipramine, nortriptyline, phenobarbital) have been labelled with metallocenic fragments in order to develop a new immunoassay method. The metallocenic fragments are cymantrenic or benchrotrenic derivatives: the linkage between the organic and organometallic moieties has been achieved by reactions between amino and acidic functional groups. All the products (metallohaptens), purified by different chromatography techniques, have been fully characterized by IR and 1H NMR spectroscopy and their mass spectra.
Efficient palladium–ferrocenylphosphine catalytic systems for allylic amination of monoterpene derivatives
2006
Ferrocenylphosphines added to [Pd(µ-Cl)(η3-C3H5)]2 dimeric precursor produce efficient catalysts to effect the allylic amination of terpenic allylacetates. Particularly convenient are tetrakis(diphenylphosphino)ferrocene and 1,1′-bis(diphenylphosphino)ferrocene, which allow the amination of allylacetates with good to excellent selectivity, and have turnover numbers as high as 80 000, for instance, for the formation of allylaniline. Herein, we report on reactions that selectively transform geranylacetate, nerylacetate, linalylacetate and perillylacetate into the corresponding allylic amines. These preparative methods give facile access to various products of great potential industrial intere…
[3.3]Ferrocenophanes with guanidine bridging units as multisignalling receptor molecules for selective recognition of anions, cations, and amino acid…
2007
The synthesis, electrochemical, and optical properties of a new [3.3]ferrocenophane framework in which two ferrocene subunits, with similar electronic environments, are linked through two substituted guanidine moieties, are reported. The receptors 4-7 have been prepared in good yields by the reaction of bis(carbodiimide) 3 with primary amines. This architecture is exceptionally "tunable" because a variety of "legs" may be appended to the basic [3.3]ferrocenophane scaffold to give a wide range of signaling units. These receptors show remarkable ion-sensing properties, due to the presence of a redox active unit (ferrocene), and an amphoteric binding site (guanidine). In this nitrogen-rich str…
Estimation of free energies of anion transfer from solid-state electrochemistry of alkynyl-based Au(I) dinuclear and Au(I)–Cu(I) cluster complexes co…
2011
A method is presented to determine the free energy for anion transfer between two solvents. This is based on solid-state electrochemistry of alkynyl-based dinuclear Au(I) complexes (AuC2R)2PPh2C6H4PPh2 (L1: R=Fc; L2: R=C6H4Fc) and heterometallic Au(I)–Cu(I) [{Au3Cu2 (C2R)6}Au3(PPh2C6H4PPh2)3](PF6)2 (L3: R=Fc; L4: R=C6H4Fc) complexes. These compounds exhibit a reversible ferrocenyl-centred solid-state oxidation processes involving anion insertion in contact with aqueous, MeOH and MeCN electrolytes. Voltammetric data can be used for a direct measurement of the free energy of ion transfer using midpeak potentials in solutions of suitable salts in the solvents separately or in mixtures of the s…
Electrochemically assisted anion insertion in Au(I)–Cu(I) heterotrimetallic clusters bearing ferrocenyl groups: Application to the fluoride/chloride …
2010
The heterotrimetallic Au(I)–Cu(I) aggregate [{Au3Cu2(C2C6H4Fc)6}Au3(PPh2C6H4PPh2)3](PF6)2 exhibits a well-defined solid state electrochemistry in contact with aqueous media, based on ferrocenyl-centred oxidation processes involving anion insertion. Upon attachment of microparticulate deposits of the cluster to graphite electrodes, distinctive electrochemical responses can be obtained for fluoride and chloride ions in aqueous media. Keywords: Heterometallic clusters, Gold, Copper, Fluoride/chloride discrimination, Electrochemical anion insertion
An easy route to 1-germaindenes via a transmetallation zirconiumgermanium reaction
1993
Abstract Several 1-zirconaindenes ( 4 ) have been obtained easily by heating phenylmethylzirconocene with various symmetrical (R R′ CH 3 , C 2 H 5 , n-C 3 H 7 , Si(CH 3 ) 3 and unsymmetrical (R CH 3 , R′ Si(CH 3 ) 3 ) alkynes (RCCR′). Under similar experimental conditions, the ynamine, diethylaminotrimethylsilylethyne, led to a regioselective reaction. From the X-ray structure of the zirconaindene product, the trimethylsilyl group was found close to the zirconium atom. Compounds 4 with germanium tetrachloride afford new 1-germaindenes ( 7 ) characterized by 1 H and 13 C NMR and mass spectrometry, in good yield.
Preparative, structural, and electrochemical investigations on peralkylated niobocene dichlorides and difluorides
1994
CP(dagger)2NbCl2 (CP(dagger) = 175-C5Me4Et) (1b) was synthesized from NbCl5 and a slight excess of Cp(dagger)Li and NaBH4. Its electrochemical (2 e-, E1/2 = -1.6 V) and chemical reduction (2 equiv of Na/Hg) was studied showing that peralkylation of the Cp ligand facilitates two-electron reduction compared to less substituted CP2NbHal2 derivatives. The reduced solutions of CP*2NbCl2 (CP* = C5Me5) (1a) and of lb were shown by means of EPR spectroscopy to contain two new paramagnetic species 1A,B for which bent niobocene (A(Nb) = 100 G) and fulvene-like structures (A(Nb) = 55 G) are proposed. The high reduction potential of these species led in their reaction with HPF6 to the first stable difl…