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See detailHomobimetallic Ethylene− and Vinylidene−Ruthenium Complexes for ATRP
Borguet, Yannick ULg; Delaude, Lionel ULg; Demonceau, Albert ULg

in Matyjaszewski, Krysztof; Sumerlin, Brent S.; Tsarevsky, Nicolay V. (Eds.) Progress in Controlled Radical Polymerization: Mechanisms and Techniques (2012)

The catalytic activity of a series of homobimetallic ruthenium complexes of the type [(p-cymene)Ru(μ-Cl)3RuCl(L)(L′)] [L = C2H4 or a vinylidene ligand (=C=CHR); L′ = PPh3, PCy3, or an N-heterocyclic ... [more ▼]

The catalytic activity of a series of homobimetallic ruthenium complexes of the type [(p-cymene)Ru(μ-Cl)3RuCl(L)(L′)] [L = C2H4 or a vinylidene ligand (=C=CHR); L′ = PPh3, PCy3, or an N-heterocyclic carbene ligand] was determined by investigating the atom transfer radical polymerisation of methyl methacrylate. The results clearly demonstrate that the ligands strongly affect the ability of the ruthenium complexes to favour the occurrence of a well-behaved ATRP. [less ▲]

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See detailHomobimetallic Ruthenium Vinylidene, Allenylidene, and Indenylidene Complexes: Synthesis, Characterization, and Catalytic Studies
Sauvage, Xavier ULg; Borguet, Yannick ULg; Zaragoza, Guillermo et al

in Advanced Synthesis & Catalysis (2009), 351(3), 441-455

Four homobimetallic ruthenium-(p-cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade ... [more ▼]

Four homobimetallic ruthenium-(p-cymene) complexes bearing a tricyclohexylphosphine ligand and polyunsaturated carbon-rich fragments were obtained via a vinylidene-allenylidene-indenylidene cascade pathway from the ethylene complex [(p-cymene)Ru(mu-Cl)(3)RuCl(PCy3)(eta(2)-C2H4)] (7a). All the products were isolated and fully characterized by IR and NMR spectroscopies. The molecular structure of the indenylidene complex 11 was determined by X-ray crystallographic analysis. The catalytic activity of the four complexes was probed in various types of olefin metathesis reactions and compared with those of a related homobimetallic ruthenium-benzylidene complex, as well as first, second, and third generation monometallic Grubbs catalysts. In the ring-closing metathesis (RCM) of diethyl diallylmalonate, the homobimetallic ruthenium-indenylidene complex 11. outperformed all the ruthenium-benzylidene complexes under investigation and was only slightly less efficient than its monometallic parent. Cross-metathesis experiments with ethylene showed that deactivation of ruthenium-benzylidene or indenylidene complexes was due to the rapid bimolecular decomposition of methylidene active species into ethylene complex 7a. Vinylidene and allenylidene complexes were far less efficient catalyst precursors for ring-opening metathesis polymerization (ROMP) or RCM and remained inert under an ethylene atmosphere. Their catalytic activity was, however, substantially enhanced upon addition of an acidic co-catalyst that most likely promoted their in situ transformation into indenylidene species. Due to its straightforward synthesis and high metathetical activity, homobimetallic ruthenium-indenylidene complex 11 is a valuable intermediate for the preparation of the Hoveyda-Grubbs catalyst [Cl2Ru(PCy3)(=CH-o-O-i-PrC6H4)] via stoichiometric cross-metathesis with 2-isopropoxystyrene. ne procedure did not require any sacrificial phosphine and the transition metal not incorporated into the final product was easily recovered and recycled at the end of the process. [less ▲]

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See detailHomobimetallic Ruthenium-Arene Complexes Bearing Vinylidene Ligands Synthesis, Characterization, and Catalytic Application in Olefin Metathesis
Borguet, Yannick ULg; Sauvage, Xavier ULg; Zaragoza, Guillermo et al

in Organometallics (2010), 29(24), 6675-6686

Five new arylvinylidene complexes with substituents ranging from electron donating to strongly withdrawing (p OMe p Me p Cl p CF3 and m (CF3)(2)) were isolated in high yields by reacting [(p cymene)Ru(mu ... [more ▼]

Five new arylvinylidene complexes with substituents ranging from electron donating to strongly withdrawing (p OMe p Me p Cl p CF3 and m (CF3)(2)) were isolated in high yields by reacting [(p cymene)Ru(mu Cl)(3)RuCl(eta(2) C2H4)(PCy3)] (3) with the corresponding phenylacetylene derivatives The known phenylvinylidene complex [(p cymene)Ru(mu Cl)(3)RuCl(=C=CHPh)(PCy3)] (5) was also obtained from [RuCl2(p cymene)](2) tricyclohexylphosphine and phenylacetylene under microwave irradiation The influence of the remote aryl substituents on structural features was investigated by IR NMR and XRD spectroscopes A very good linear relationship was observed between the chemical shift of the vinylidene alpha carbon atom and the Hammett sigma constants of the aryl group substituents The catalytic activity of the six homobimetallic complexes was probed in various types of olefin metathesis reactions Unsubstituted phenylvinylidene compound 5 served as a lead structure for these experiments Its reaction with norbornene afforded high molecular weight polymers with a broad polydispersity index and mostly trans double bonds Aluminum chloride was a suitable cocatalyst for the ring opening metathesis polymerization of cyclooctene and led to the formation of high molecular weight polyoctenamer with a rather narrow polydispersity index (M-w/M-n = 1 25) and an almost equimolar proportion of cis and trans double bonds No major changes were observed in the polymer yields and microstructures when complexes bearing donor groups on their aryl rings were employed as catalyst precursors On the other hand compounds bearing strongly electron withdrawing substituents were significantly less active Model vinylidene compound 5 and its ruthenium-ethylene parent (3) both required the addition of phenylacetylene to achieve the ring closing metathesis of diethyl 2 2 diallylmalonate Thus the role of this terminal alkyne cocatalyst goes beyond the facile replacement of the eta(2) alkene ligand with a vinylidene fragment [less ▲]

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See detailHomobimetallic ruthenium-N-heterocyclic carbene complexes for olefin metathesis
Sauvage, Xavier ULg; Demonceau, Albert ULg; Delaude, Lionel ULg

in Imamoglu, Yavuz; Dragutan, Valerian (Eds.) Metathesis Chemistry. From nanostructure design to synthesis of advanced materials (2007)

In this chapter, the synthesis and catalytic activity towards olefin metathesis of homobimetallic ruthenium (Ru)-alkylidene, -cyclodiene or -arene complexes bearing phosphine or N-heterocyclic carbene ... [more ▼]

In this chapter, the synthesis and catalytic activity towards olefin metathesis of homobimetallic ruthenium (Ru)-alkylidene, -cyclodiene or -arene complexes bearing phosphine or N-heterocyclic carbene (NHC) ligands are reviewed. Emphasis is placed on the last category of bimetallic compds. Three representatives of this new type of mol. scaffold were investigated. Thus, [(p-cymene)Ru(m-Cl)3RuCl (h2-C2H4)(L)] complexes with L = PCy3 (15a), IMes (16a), or IMesCl2 (16b) were prepd. They served as catalyst precursors for cross-metathesis (CM) of various styrene derivs. These expts. revealed the outstanding aptitude of complex 16a (and to a lesser extent of 16b) to catalyze olefin metathesis reactions. Contrary to monometallic Ru-arene complexes of the [RuCl2(p-cymene)(L)] type, the new homobimetallic species did not require the addn. of a diazo compd. nor visible light illumination to initiate the ring-opening metathesis of norbornene or cyclo-octene. When di-Et 2,2-diallylmalonate and N,N-diallyltosylamide were exposed to 16a,b, a mixt. of cycloisomerization and ring-closing metathesis (RCM) products was obtained in a nonselective way. Addn. of phenylacetylene enhanced the metathetical activity while completely repressing the cycloisomerization process. [less ▲]

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See detailHomobimetallic ruthenium-N-heterocyclic carbene complexes: Synthesis, characterization, and catalytic applications
Sauvage, Xavier ULg; Borguet, Yannick ULg; Noels, Alfred ULg et al

in Advanced Synthesis & Catalysis (2007), 349(1-2), 255-265

Two new homobimetallic ruthenium-arene complexes [(p-cymene)Ru(mu-Cl)(3)RuCl(eta(2)-C2H4)(L)], where L=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (3a) or 1,3-bis(2,4,6-trimethylphenyl)-4,5 ... [more ▼]

Two new homobimetallic ruthenium-arene complexes [(p-cymene)Ru(mu-Cl)(3)RuCl(eta(2)-C2H4)(L)], where L=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (3a) or 1,3-bis(2,4,6-trimethylphenyl)-4,5-dichloroimidazolin-2-ylidene (3b), were isolated in high yields upon heating a toluene solution of [RuCl2 (p-cymene)](2) with 1 equivalent of carbene ligand under an ethylene atmosphere. They were characterized by NMR and TGA. Their catalytic activity was investigated in the atom transfer radical polymerization of vinyl monomers. In the polymerization of methyl methacrylate, complex 3a displayed faster reaction rates than 3b and the related phosphine-based complex 2a (L=tricyclohexylphosphine), although control was more effective with the latter catalyst. When n-butyl acrylate or styrene served as monomer, a major shift of reactivity was observed between complex 2a that promoted controlled radical polymerization, and complexes 3a or 3b that favored metathetical coupling. Further homocoupling experiments with various styrene derivatives confirmed the outstanding aptitude of complex 3a (and to a lesser extent of 3b) to catalyze olefin metathesis reactions. Contrary to monometallic ruthenium-arene complexes of the [RuCl2(p-cymene)(L)] type, the new homobimetallic species did not require the addition of a diazo compound or visible light illumination to initiate the ring-opening metathesis of norbornene or cyclooctene. When alpha,omega-dienes were exposed to 3a or 3b, a mixture of cycloisomerization and ring-closing metathesis products was obtained in a non-selective way. Addition of a terminal alkyne co-catalyst enhanced the metathetical activity while completely repressing the cycloisomerization process. Thus, quantitative conversions of diethyl 2,2-diallylmalonate and N,N-diallyltosylamide were achieved within 2 h at room temperature using 2 mol % of catalyst precursor 3 a and 6 mol % of phenylacetylene. [less ▲]

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See detailHomochiral, Helical Supramolecular Metal-Organic Frameworks Organized by Strong π···π Stacking Interactions: Single-Crystal to Single-Crystal Transformations in Closely Packed Solids
Reger, Daniel L; Horger, Jacob J; Smith, Mark D et al

in Inorganic Chemistry (2011), 50

Enantiopure, trifunctional carboxylate ligands synthesized by linking the strong π3 3 3 π stacking 1,8-naphthalimide supramolecular synthon to three naturally occurring amino acids using the azide/alkyne ... [more ▼]

Enantiopure, trifunctional carboxylate ligands synthesized by linking the strong π3 3 3 π stacking 1,8-naphthalimide supramolecular synthon to three naturally occurring amino acids using the azide/alkyne click reaction have been prepared [amino acid = glycine (Lgly -), alanine (Lala -), and serine (Lser -)]. These ligands have been used to form complexes of the formula [M(Lamino acid)2(4,40-bipy)(H2O)2] 3 xH2O (M = Fe, Co,Ni, Cu, Zn; x = 4.25-5.52) when mixed with an appropriate metal salt and 4,40-bipyridine by layeringmethods. These complexes are isostructural, with the centralmetal atomcoordinated to two κ1-carboxylate ligands, two water molecules, and one end each of two 4,40-bipyridine ligands in a distorted octahedral environment. Each ligand is oriented in a trans arrangement. These complexes all have homochiral, helical, supramolecular, three-dimensional metal-organic framework structures, with the helical organization of the individual metallic units held together solely by strong, noncovalent π3 3 3 π stacking interactions of the naphthalimide; the other two dimensions are organized mainly by the bipyridine ligands. The helices are extremely large; one turn of the helix travels ∼60 and has a diameter of ca. 40 . For the achiral ligand Lgly -, the nickel complex forms two types of homochiral crystals in the same tube, a clear example of spontaneous resolution. Despite the large size of the individual helices, they are tightly interconnected and nestled closely together. Part of the interconnection comes from the interstitial watermolecules held inside the framework of the complexes in isolated pockets by hydrogen-bonding interactions. For both [Cu(Lala)2(4,40-bipy)(H2O)2] 3 4.25H2O and [Co(Lser)2(4,40-bipy)(H2O)2] 3 4.68H2O, the interstitial water molecules can be removed by placing the crystals under a vacuum for several hours, a process that can be reversed by exposure to atmospheric moisture. This removal/reintroduction of the interstitial water molecules takes place with no loss of crystallinity, representing dramatic examples of single-crystal to single-crystal transformations. The structures undergo little change other than the pockets holding the interstitial water molecules in the hydrated complexes become void spaces in the dehydrated complexes. The removal/reintroduction of the watermolecules in these closely packed solids is facilitated by the “soft”π3 3 3 πstacking interactions organizing one dimension of the structures. The observed magnetic and M€o ssbauer spectral properties are typical of isolated, magnetically dilute, paramagnetic pseudooctahedral divalent transition-metal complexes. [less ▲]

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See detailHomocysteine et risque cardio-vasculaire
Lutteri, Laurence ULg; Chapelle, Jean-Paul ULg; Gielen, Jean-Louis ULg

in Revue Médicale de Liège (1999), 54(6), 541-7

Homocystinuria is an uncommon genetic disease characterized by a marked increase of serum homocysteine (HCY), an intermediate of methionine metabolism. In patients with homocystinuria ... [more ▼]

Homocystinuria is an uncommon genetic disease characterized by a marked increase of serum homocysteine (HCY), an intermediate of methionine metabolism. In patients with homocystinuria, hyperhomocysteinemia promotes the development of atherosclerotic lesions and is responsible for premature coronary artery disease. Recently, several studies have also demonstrated that moderate hyperhomocysteinemia--not necessarily linked to an inborn metabolic defect--may also be considered as an independant risk factor for cardiovascular disease. The main mechanisms of HCY atherogenic action are thought to be LDL oxydation, inhibition of vascular endothelium growth combined with stimulation of smooth muscular cells proliferation, and interference with the coagulation and fibrinolytic systems. Cofactors of key enzymes in HCY metabolism, folic acid, vitamin B12 and vitamin B6, may be given, alone or in combination, for the treatment of hyperhomocysteinemia. Homocysteinemia can be assessed by basal plasma HCY concentration and/or by HCY levels measured after a methionine loading test. Mainly measured till now in specialized laboratories using rather complex techniques (HPLC, GCMS, amino acid analyser ...), HCY determination is today spreading widely owing to the development of automated immunoassays. [less ▲]

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See detailHomogénéiser les acquis de stage. Expérience en logopédie.
Maillart, Christelle ULg

Learning material (2013)

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See detailHomogeneous and fractal behavior of superconducting fluctuations in the electrical resistivity of granular ceramic superconductors
Ausloos, Marcel ULg; Clippe, Paulette ULg; Laurent, Christian

in Physical Review B (1990), 41(13), 9506-9509

Experimental data show that the electrical-resistivity temperature derivative diverges in a different manner in the granular ceramic superconductors YBa2Cu3O7-y and Bi1.75Pb0.25Ca2Sr2Cu3O10-y. Critical ... [more ▼]

Experimental data show that the electrical-resistivity temperature derivative diverges in a different manner in the granular ceramic superconductors YBa2Cu3O7-y and Bi1.75Pb0.25Ca2Sr2Cu3O10-y. Critical exponents are extracted and explained. The dimensionality of anomalous superconductivity fluctuations is deduced. A homogeneous case and a self-similar (fractal) behavior can occur and are found. They correspond to different values of the superconductivity s and some percolation p coherence-length ratio. The results indicate that superconductivity percolation is achieved through surface connection rather than through path connection. [less ▲]

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See detailHomogeneous Lyapunov Functions and Necessary Conditions for Stabilization
Sepulchre, Rodolphe ULg; Aeyels, D.

in Journal of mathematics for control, signal and systems (1996), 9(1), 34-58

We provide necessary conditions for the stabilization of nonlinear control systems with the additional requirement that a time-invariant homogeneous Lyapunov function exists for the closed-loop system.

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See detailHomogenisation of Windings and Laminations in Time-Domain Finite-Element Modeling of Electrical Machines
Gyselinck, Johan; Geuzaine, Christophe ULg; Vazquez Sabariego, Ruth ULg

in Proceedings of the 15th Biennial IEEE Conference on Electromagnetic Field Computation (CEFC2012) (2012, November)

This paper deals with time-domain homogenisation of multi-turn windings and laminated cores in 2D and 3D finite- element (FE) modelling of rotating electrical machines. Herein the number of additional ... [more ▼]

This paper deals with time-domain homogenisation of multi-turn windings and laminated cores in 2D and 3D finite- element (FE) modelling of rotating electrical machines. Herein the number of additional degrees of freedom (auxiliary field variables) in the homogenised regions can be fixed depending on the extent of the eddy current effects and on the desired accuracy. The homogenisation technique is illustrated and validated by means of a 2D model of a switched reluctance motor. Global quantities, such as the phase impedance, converge very well to those produced by a precise but very expensive 3D model. [less ▲]

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See detailHomogenization of fibre reinforced composite with gradient enhanced damage model
Wu, Ling ULg; Noels, Ludovic ULg; Adam, Laurent et al

in Hogge, Michel; Van Keer, Roger; Dick, Erik (Eds.) et al Proceedings of the 5th International Conference on Advanded COmputational Methods in Engineering (ACOMEN2011) (2011, November)

Classical finite element simulations face the problems of losing uniqueness and strain localization when the strain softening of materials is involved. Thus, when using continuum damage model or ... [more ▼]

Classical finite element simulations face the problems of losing uniqueness and strain localization when the strain softening of materials is involved. Thus, when using continuum damage model or plasticity softening model, numerical convergence will not be obtained with the refinement of the finite element discretization when strain localization occurs. Gradient-enhanced softening and non-local continua models have been proposed by several researchers in order to solve this problem. In such approaches, high-order spatial gradients of state variables are incorporated in the macroscopic constitutive equations. However, when dealing with complex heterogeneous materials, a direct simulation of the macroscopic structures is unreachable, motivating the development of non-local homogenization schemes. In this work, a non-local homogenization procedure is proposed for fiber reinforced materials. In this approach, the fiber is assumed to remain linear elastic while the matrix material is modeled as elasto-plastic coupled with a damage law described by a non-local constitutive model. Toward this end, the mean-field homogenization is based on the knowledge of the macroscopic deformation tensors, internal variables and their gradients, which are applied to a micro- structural representative volume element (RVE). Macro-stress is then obtained from a homogenization process. [less ▲]

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See detailHomogenization of form- wound windings in finite element modelling of electrical machines
Gyselinck, Johan; Dular, Patrick ULg; Sadowski, Nelson et al

in IEEE Transactions on Magnetics (2010), 46(8), 2852-2855

In this paper, the authors deal with the finite-element (FE) modeling of eddy-current effects in form-wound windings of electrical machines using a previously proposed general frequency- and time-domain ... [more ▼]

In this paper, the authors deal with the finite-element (FE) modeling of eddy-current effects in form-wound windings of electrical machines using a previously proposed general frequency- and time-domain homogenization method. By way of demonstration and validation, a real-life 1250-kW induction machine with double-layer stator winding is considered. The skin and proximity effects in one stator conductor (copper bar) are first quantified by means of a simple low-cost FE model, leading to complex and frequency-dependent coefficients for the homogenized winding (reluctivity for proximity effect and conductivity or resistance for skin effect). These complex coefficients are subsequently translated into real-valued and constant coefficients that allow for time-domain homogenization when introducing a limited number of additional degrees of freedom in the FE model. All results obtained with the homogenized model (considering one conductor or a complete slot) agree well with those produced by a brute-force approach (modeling and finely discretizing each conductor). [less ▲]

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See detailHomogenization of laminations and windings in low frequency electromagnetism
V Sabariego, Ruth ULg

Scientific conference (2009, September)

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See detailHomogenization techniques in electromagnetics
Vazquez Sabariego, Ruth ULg

Scientific conference (2011, August)

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See detailHomogenization techniques in low frequency electromagnetics
Vazquez Sabariego, Ruth ULg

Scientific conference (2011, January 03)

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See detailHomogenization techniques in low frequency problems
V Sabariego, Ruth ULg

Scientific conference (2008, March)

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See detailHomogenization with propagation of instabilities through the different scales
Noels, Ludovic ULg; Wu, Ling ULg; Nguyen, Van Dung ULg et al

Scientific conference (2014, January 31)

In this work, multi-scale methods with strain softening are developed in the contexts of damage modeling for composite laminates and of buckling analyses in cellular materials. First, an anisotropic ... [more ▼]

In this work, multi-scale methods with strain softening are developed in the contexts of damage modeling for composite laminates and of buckling analyses in cellular materials. First, an anisotropic gradient–enhanced continuum damage model is embedded in a mean–field homogenization (MFH) process for elasto-plastic composites. The homogenization procedure is based on the newly developed incremental secant mean-field homogenization formulation, for which the residual stress and strain states reached in the phases upon a fictitious elastic unloading are considered as starting point to apply the secant method. The mean stress fields in the phases are then computed using isotropic secant tensors, which are naturally used to define the Linear Comparison–Composite The resulting multi– scale model is then applied to study the damage process at the meso–scale of laminates, and in particular the damaging of plies in a composite stack. By using the gradient–enhanced continuum damage model, the problem of losing uniqueness upon strain softening is avoided. Second, an efficient multi–scale finite element framework capturing the buckling instabilities in cellular materials is developed. As a classical multi–scale computational homogenization scheme loses accuracy with the apparition of the macroscopic localizations resulting from the micro–buckling, the second order multi–scale computational homogenization scheme is considered. This second–order computational framework is enhanced with the following novelties so that it can be used for cellular materials. At the microscopic scale, the periodic boundary condition is used because of its efficiency. As the meshes generated from cellular materials exhibit a large void part on the boundaries and are not conforming in general, the classical enforcement based on the matching nodes cannot be applied. A new method based on the polynomial interpolation2 without the requirement of the matching mesh condition on opposite boundaries of the representative volume element (RVE) is developed. Next, in order to solve the underlying macroscopic Mindlin strain gradient continuum of this second–order scheme by the displacement–based finite element framework, the treatment of high order terms is based on the discontinuous Galerkin (DG) method to weakly impose the C1-continuity. Finally, as the instability phenomena are considered at both scales of the cellular materials, the path following technique is adopted to solve both the macroscopic and microscopic problems. [less ▲]

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See detailHomogenizing clinical training through ‘à la carte’ self-directed learning
Maillart, Christelle ULg; Grevesse, Pascale; Wiot, Nathalie

Poster (2012, May 25)

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See detailHomoleptic Diphosphacyclobutadiene Complexes [M(4-P2C2R2)2]x- (M=Fe, Co; x=0, 1),
Wolf, Robert; Ehlers, Andreas W; Khusniyarov, Marat M et al

in Chemistry : A European Journal (2010), 16

The preparation and comprehensive characterization of a series of homoleptic sandwich complexes containing diphosphacyclobutadiene ligands is reported. Compounds [K([18]crown-6)(thf)2][Fe(h4- P2C2tBu2)2 ... [more ▼]

The preparation and comprehensive characterization of a series of homoleptic sandwich complexes containing diphosphacyclobutadiene ligands is reported. Compounds [K([18]crown-6)(thf)2][Fe(h4- P2C2tBu2)2] (K1), [K([18]crown-6)-(thf)2][Co(h4-P2C2tBu2)2] (K2), and [K([18]crown-6)(thf)2][Co(h4- P2C2Ad2)2] (K3, Ad=adamantyl) were obtained from reactions of [K([18]crown-6)(thf)2][M(h4-C14H10)2] (M=Fe, Co) with tBuC P (1, 2), or with AdC P (3). Neutral sandwiches [M(h4-P2C2tBu2)2] (4: M=Fe 5: M= Co) were obtained by oxidizing 1 and 2 with [Cp2Fe]PF6. Cyclic voltammetry and spectro-electrochemistry indicates that the pairs [M(h4-P2C2tBu2)2] / [M(h4-P2C2tBu2)2] can be reversibly interconverted by one electron oxidation and reduction, respectively. Complexes 1–5 were characterized by multinuclear NMR, EPR (1 and 5), UV/Vis, and Mçssbauer spectroscopies (1 and 4), mass spectrometry (4 and 5), and microanalysis (1–3). The molecular structures of 1–5 were determined by usingX-ray crystallography. Essentially D2dsymmetric structures were found for all five complexes, which show the two 1,3-diphosphacyclobutadiene rings in a staggered orientation. Density functional theory calculations revealed the importance of covalent metal–ligand p bonding in 1–5. Possible oxidation state assignments for the metal atoms are discussed. [less ▲]

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