1,720,978 research outputs found
Low hapticity intermediates in the carbonylation of (eta5-2,6-dimethyl-5-hydro-s-indacenide)-Ir(eta4-COD)
No full textThe isomeric (eta(1)-5-hydro-2,6-dimethyl-s-indacenide)-Ir(eta(4)-COD)(CO)(2) and (eta(1)-7-hydro-2,6-dimethyl-s-indacenide)-Ir(eta(4)-COD)(CO)(2)) complexes are produced in a ii I ratio in the first step of the carbonylation reaction of (eta(5)-2,6-dimethyl-5-hydro-s-indacenide)-Ir(eta(4)-COD) at 233 K. At 243 K, in the presence of excess CO, they slowly convert into the isomeric (eta(1)-5-hydro-2,6-dimethyl-s-indacenide)-Ir[eta(2)-COD)(CO)(3)) and (eta(1)-7-hydro-2,6-dimethyl-s-indacenide]-Ir(eta(2)-COD)(CO)(3). The unprecedented eta(2)-coordination of COD towards iridium has been detected both by conventional variable temperature 1D H-1 NMR spectroscopy and by a single-temperature 2D EXSY experiment
103Rh NMR Chemical Shifts in Organometallic Complexes: A Combined Experimental and Density Functional Study
No full textExperimental 103Rh NMR chemical shifts of mono- and binuclear rhodium(I) complexes containing s- or as-hydroindacenide and indacenediide bridging ligands with different ancillary ligands (1,5-cyclooctadiene, ethylene, carbonyl) are presented. A protocol, based on density functional theory calculations, was established to determine 103Rh NMR shielding constants in order to rationalise the effects of electronic and structural variations on the spectroscopic signal, and to gain insight into the efficiency of this computational method when applied to organometallic systems. Scalar and spin–orbit relativistic effects based on the ZORA (zeroth order regular approximation) level have been taken into account and discussed. A good agreement was found for model compounds over a wide range of chemical shifts of rhodium (≈10 000 ppm). This allowed us to discuss the experimental and calculated δ(103Rh) in larger complexes and to relate it to their electronic structure
Electronic communication in heterobinuclear organometallic complexes through unsaturated hydrocarbon bridges
No full textMuch of the interest about the construction of model compounds suitable for investigating the phenomena associated with the interaction of two or more metal centers, the so-called cooperative effect, has been concentrated on homobimetallic complexes and less attention has been paid to the class of heterobimetallic derivatives. This review will feature experimental detection and the effects of the electronic communication in heterobinuclear organometallic complexes through unsaturated hydrocarbon bridges. The described systems are classified according to the nature of the bridging ligand, in three main groups: (i) carbon sigma-bonded molecular wires; (ii) fulvalene and fulvalene-like bridges; (iii) fused delocalized polycyclic bridges. In this contribution, we discuss the flexibility of heterobimetallic complexes, and more in general of asymmetric bimetallic species, in terms of tailoring the cooperative effects, i.e. of controlling and tuning the reactivity of one metal center by acting on the adjacent one. Satisfactory quantitative estimate of the degree of metal to metal communication through the bridging ligand is obtained in illustrative examples combining efficient electrochemical and spectroscopic techniques with consolidated theories. A review with almost 350 references
Charge Transfer Properties of Multi(ferrocenyl)trindenes
No full textFerrocenyl, diferrocenyl, and triferrocenyl complexes of dihydro-1H-trindene have been prepared by up to 3-fold bromide substitution of the dihydro-2,5,8-tribromo-1H-trindene halocarbon. The charge transfer properties of their mono-, di-, and tricationic derivatives were investigated. The cations of this new family of multi(ferrocenyl)trindene complexes were generated by chemical oxidation using (acetylferrocenium)(BF4) as the oxidative agent and monitored in the visible, IR and near-IR regions. The charge transfer bands in the near-IR spectra are rationalized in the framework of the Marcus–Hush theory. In particular, the triferrocenyl complexes display a redox chemistry that can be switched from a unresolved three-electron oxidation to two consecutive one-electron and two near simultaneously occurring one-electron oxidations by changing the supporting electrolyte from [nBu4N][PF6] to [nBu4][B(C6F5)4]. In addition, the introduction of the third ferrocenyl group increases the strength of the metal–metal interaction with respect to that of the structurally related diferrocenyl system
Chemical communication induced by intermolecular electron transfer in heterobimetallic ferrocenyl-indenyl-Cr(CO)3 complexes
No full textBenzodithiophene and benzotrithiophene as Ï cores for two-and three-blade propeller-shaped ferrocenyl-based conjugated systems
Full text linkThe syntheses of linear and star-shaped bis- and tris(ferrocenyl) derivatives of benzo[1,2-b:4,5-b′]dithiophene and benzo[1,2-b:3,4-b′:5,6-b′′]trithiophene are achieved through one-pot CuI/TMEDA-catalyzed (TMEDA = tetramethylethylenediamine) multiple annulations of bromoethynylbenzenes with sodium sulfide. In addition, the preparation of the parent benzotrithiophene in a good yield with a short reaction time is achieved through the threefold annulation of 1,3,5-trifluoro- Introduction Benzo[b]thiophene (BT, Scheme 1) and its derivatives are an important class of fused thiophene compounds owing to their wide range of biological properties[1,2] and various applications in materials science.[3] Scheme 1. Fused thiophene compounds: benzo[b]thiophene (BT), benzo- [1,2-b:4,5-b′]dithiophene (BDT), and benzo[1,2-b:3,4-b′:5,6-b′′]trithiophene (BTT). In particular, (multi)thiophene fused aromatic compounds are attracting interest as promising electronic materials for organic conductors,[4] organic light-emitting diodes,[5] photovoltaic cells,[6] and field-effect transistors.[7] For this reason, thiophene- based π-conjugated oligomers have been investigated widely as organic semiconductors.[8] Recently, much effort has been focused on benzo[1,2-b:4,5-b′]- dithiophene (BDT) and benzo[1,2-b:3,4-b′:5,6-b′′]trithiophene (BTT, Scheme 1) as potential π cores for a new class of organic semiconductors as they contain two or three identical thiophene moieties with C2h or C3h symmetries that enable twoand three-dimensional molecular extensions. [a] Department of Chemical Sciences, University of Padova Via Marzolo 1, 35131 Padova, Italy E-mail: [email protected] http://www.chimica.unipd.it/ Supporting information and ORCID(s) from the author(s) for this article are available on the WWW under https://doi.org/10.1002/ejoc.201701045. Eur. J. Org. Chem. 2017, 5966–5974 5966 © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2,4,6-tris(trimethylsilyl)ethynylbenzene. The computed structural and electronic features of these ferrocenyl derivatives as well as their UV/Vis spectra and electrochemistry are discussed, and the results provide insights into the effect of the presence of three rather than two ferrocenyl units. To the best of our knowledge, 2,5,8-tris(ferrocenyl)benzo[1,2-b;3,4-b′;5,6-b′′]trithiophene is the first organometallic complex containing benzotrithiophene
Key multi(ferrocenyl) complexes in the interplay between electronic coupling and electrostatic interaction
Full text linkIn this review, the properties of the most significant examples of multi(ferrocenyl) cations containing a number of ferrocenyl units from two to six are discussed and the results are compared with the outcomes of some of our recent studies on conjugated ferrocenyl complexes, in order to give an overview of how the nature of the bridging ligand, the distance between the redox-active centres, and the medium affect the electronic and electrostatic properties of the molecule
Heterobimetallic Iron-Rhodium Complexes. The Synthesis and Characteristics of CpFe-(mu-eta:eta-as-Indacene-diide)-RhL2 [L2 = COD, NBD, (Ethylene)2]
No full textThe heterobimetallic CpFe(mu-eta(5): eta(5)-as-indacenediide)RhL2 complexes (L-2 = COD (2), NBD (3), (ethylene)2 (4)) have been obtained from metalation of the mononuclear lithium CpFe(eta(5)-as-indacenediide) with [Rh(mu-Cl)L-2](2). Mixtures of syn and anti heterobimetallic complexes were formed and fully characterized by 2D NMR spectroscopy. The reactivity at the rhodium center is greatly influenced by the presence of the ferrocenyl moiety. The voltammetric behavior and the optical spectra are in favor of the existence of significant electronic interactions between the two metals
Designing molecules for metal-metal electronic communication: Synthesis and molecular structure of the couple of heterobimetallic isomers [eta(6)-(2-ferrocenyl)indenel-Cr(CO)(3) and [eta(6)-(3-ferrocenyl)indenel-Cr(CO)(3)
No full textThe heterobinuclear isomers [eta(6)-(2-ferrocenybindene]-Cr(CO)(3) (1) and [eta(6)-(3-/errocenyl)indene]-Cr(CO)(3) (2) have been prepared and the crystal structure determination showed that the Fe(C5H5) and Cr(CO)(3) groups in the two molecules are disposed in different conformations with respect to the Cp-indene bridging ligand, cisoid in 1 and transoid in 2. Preliminary electrochemical (CV) and spectroscopic (IR and near-IR) results obtained for the corresponding monooxidized 1(+) and 2(+) demonstrate the existence of stronger electronic coupling in 1(+) than in 2(+)
Charge Transfer Properties in Cyclopenta[l]phenanthrene Ferrocenyl Complexes
No full textThe new complexes (2-ferrocenyl)cyclopenta[l]-phenanthrene and (2-ferrocenyl)(eta(5)-cyclopenta[l]phenanthrenyl)FeCp have been prepared and the charge transfer properties of their monocationic derivatives investigated. The cations were generated by chemical oxidation using ferrocenium(BF4) or acetylferrocenium(BF4) as the oxidative agent and monitored in the visible, IR, and near-IR regions. The electrochemistry of the two complexes and, for comparison, of the previously reported (eta(5)-cyclopenta[l]phenanthrenyl)FeCp was analyzed. The charge transfer bands in the near-IR spectral region of the monocations are rationalized in the framework of Marcus-Hush theory. In particular, the monometallic (2-ferrocenyl)cyclopenta[l]phenanthrene displays a single oxidation wave at a potential very close to that of (eta(5)-cyclopenta[l]phenanthrenyl)FeCp and its monocations exhibits a ligand-to-metal charge transfer band in the visnear-IR region. The unsymmetrical diiron species (2-ferrocenyl)(eta(5)-cyclopenta[l]phenanthrenyl)FeCp undergoes two consecutive and well-resolved one-electron oxidations producing, at the first oxidation step, a mixed-valence monocation which displays an intervalence charge transfer band in the vis-near-IR region
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