Showing papers in "European Journal of Inorganic Chemistry in 2008"
TL;DR: In this paper, the authors focus on the latest advances in homogeneous catalysis with donor-functionalised (donor = C, N, O, S or P) N-heterocyclic carbene complexes.
Abstract: This review focuses on the latest advances in homogeneous catalysis with donor-functionalised (donor = C, N, O, S or P) N-heterocyclic carbene complexes of group 9 and 10 metals. The applications of such complexes to C–C coupling reactions, alkyne and ketone hydrosilylation, olefin polymerisation, transfer hydrogenation, asymmetric hydrogenation and other catalysed reactions are discussed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
356 citations
TL;DR: In this paper, two coordination polymers constructed from magnesium and the tetratopic organic linker 2,5-dihydroxyterephthalic acid are reported, denominated CPO-26-Mg and CPO27-mg.
Abstract: Two coordination polymers constructed from magnesium and the tetratopic organic linker 2,5-dihydroxyterephthalic acid are reported, denominated CPO-26-Mg and CPO-27-Mg. The organic component carries two different types of protic functional groups. The degree of deprotonation of the organic component can be regulated by the amount of sodium hydroxide employed in the synthesis, thus determining which of the compounds forms. In CPO-26-Mg, only the carboxylic acid groups of the linker are deprotonated and take part in the construction of the three-dimensional framework. The structure is non-porous, and its topology is based on the PtS net. In CPO-27-Mg, both the carboxylic acid and the hydroxy groups are deprotonated and involved in the construction of a microporous three-dimensional framework which is based on a honeycomb motif containing large solvent-filled channels. The metal atoms are arranged in chiral chains along the intersection of the honeycomb and contain one water molecule in their coordination sphere, which allows for the creation of coordinatively unsaturated metal sites upon dehydration. CPO-27-Mg is a potentially useful lightweight adsorbent with a pore volume of 60 % of the total volume of the structure and an apparent Langmuir surface area of up to 1030 m2 g–1. Its thermal stability was investigated by thermogravimetry and variable-temperature powder X-ray diffraction, which shows framework degradation to commence at 160 °C in air, at 235 °C under nitrogen, and at 430 °C in a dynamic vacuum. Thermogravimetric dehydration and re-hydration experiments at miscellaneous temperatures indicate that it is possible to obtain open metal sites in CPO-27-Mg, but the water is more tightly bound in this material than in the previously reported isostructural nickel compound.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
304 citations
TL;DR: In this article, the use of a simple electron donor-acceptor dyad, the 9-mesityl-10-methylacridinium ion (Acr+−Mes), enables the construction of a highly efficient photocatalytic hydrogen-evolution system without an electron mediator such as MV2+, with poly(N-vinyl-2-pyrrolidone)-protected platinum nanoclusters (Pt-PVP) and NADH as a hydrogenevolution catalyst and an electron donor, respectively.
Abstract: Recent developments in photocatalytic hydrogen production by using artificial photosynthesis systems is described, together with those in hydrogen storage through the fixation of CO2 with H2. Hydrogen can be stored in the form of formic acid, which can be converted back to H2 in the presence of an appropriate catalyst. Electron donor–acceptor dyads are utilized as efficient photocatalysts to reduce methyl viologen (MV2+) by NADH (β-nicotinamide adenine dinucleotide, reduced form) analogues to produce the methyl violgen radical cation that acts as an electron mediator for the production of hydrogen. Porphyrin-monolayer-protected gold clusters that enhance the light harvesting efficiency can also be used for the photocatalytic reduction of methyl viologen by NADH analogues. The use of a simple electron donor–acceptor dyad, the 9-mesityl-10-methylacridinium ion (Acr+–Mes), enables the construction of a highly efficient photocatalytic hydrogen-evolution system without an electron mediator such as MV2+, with poly(N-vinyl-2-pyrrolidone)-protected platinum nanoclusters (Pt–PVP) and NADH as a hydrogen-evolution catalyst and an electron donor, respectively. Hydrogen thus produced can be stored in the form of formic acid (liquid) by fixation of CO2 with H2 in water by using ruthenium aqua complexes [RuII(η6-C6Me6)(L)(OH2)]2+ [L = 2,2′-bipyridine (bpy), 4,4′-dimethoxy-2,2′-bipyridine (4,4′-OMe-bpy)] and iridium aqua complexes [IrIIICp*(L)(OH2)]2+ (Cp* = η5-C5Me5, L = bpy, 4,4′-OMe-bpy) as catalysts at pH 3.0. Catalytic systems for the decomposition of HCOOH to H2 are also described. The combination of photocatalytic hydrogen generation with the catalytic fixation of CO2 with H2 and the decomposition of HCOOH back to H2 provides an excellent system for cutting CO2 emission.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
246 citations
TL;DR: In this paper, a large-scale synthesis of single-crystalline and uniform CeO2 nanorods was first realized without templates by a precipitation method at room temperature and pressure.
Abstract: A general large-scale synthesis of single-crystalline and uniform CeO2 nanorods was first realized without templates by a precipitation method at room temperature and pressure. Such nanorods have an aspect ratio of ca. 3 nm with a diameter of ca. 8 nm and a large BET specific area of 128.2 m2/g. On the basis of this, the controlled conversion of the as-prepared nanorods into nanotubes, nanowires, and nanocubes through hydrothermal reactions has been realized. Further experimental results show that the growth of nanorods is a function of the base concentration, temperature, and time. In addition, particle size measurements demonstrate that the primary nanorods grow by Ostwald ripening. It is found that CeO2 growth is faster at higher base concentration and temperature due to the accelerated ripening. During the synthesis, the formation of Ce(OH)3 intermediate species and their transformation into CeO2 have been dynamically demonstrated and are regarded as the key factors responsible for the evolution of shape. The CO oxidation properties of CeO2 nanorods, nanowires, nanotubes, and nanocubes were investigated, and CeO2 nanotubes have the best performance due to the large BET surface area and the novel inner surface. In addition, CeO2 nanorods aged for 9 d also have an excellent catalytic performance for CO oxidation due to the exposed crystal surface (110) of CeO2. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
233 citations
TL;DR: The use of metallic nanoparticles in catalysis under homogeneous conditions leads to a discussion of their catalytic nature: whether the catalyst behaves as a molecular species or, on the contrary, the metallic surface is directly involved in the reactivity as discussed by the authors.
Abstract: The use of metallic nanoparticles in catalysis under homogeneous conditions leads to a discussion of their catalytic nature: whether the catalyst behaves as a molecular species or, on the contrary, the metallic surface is directly involved in the reactivity. This dilemma is intrinsically associated to the kinetic stability of the nanoclusters, favouring their agglomeration, and also to the formation of molecular species by reaction of the atoms placed at low-coordination positions at the metallic surface. In particular, for palladium-catalyzed processes, a large number of contributions have been reported in the last decade involving nanoparticles, but few of them analyze the mechanistic aspects. The present review aims to collect the more relevant research carried out in catalysis involving palladium nanoparticles in the liquid phase and addressing the nature of the catalytically active species. This kind of work is mainly focused on hydrogenation and C–C coupling processes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
189 citations
TL;DR: The increasing use of polyoxometalates in the fields of material sciences, catalysis, and biology has raised the interest in chirality of such systems as discussed by the authors, and a review provides a summary of the different strategies followed.
Abstract: The increasing use of polyoxometalates in the fields of material sciences, catalysis, and biology has raised the interest in chirality of such systems. This review provides a summary of the different strategies followed: i) chirality in solid-state arrangements, ii) chiral polyoxometalate frameworks, and iii) chiral polyoxometalate–organic hybrids. Through the discussion of selected examples, an outline for future work is drawn. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
179 citations
TL;DR: In this paper, the emerging class of hybrid nanocrystals (HNCs), in which domains of different materials are interconnected through inorg junctions in defined spatial arrangements, is reviewed.
Abstract: A review. Recent progress of colloidal chem. in the prepn. of multimaterial nanostructures incorporating transition-metal oxides is reviewed. Attention is focused on the emerging class of hybrid nanocrystals (HNCs), in which domains of different materials are interconnected through inorg. junctions in defined spatial arrangements. The level of expertise so far achieved in the prepn. of single-material NCs with finely tuned geometric parameters was further extended into elegant "seeded growth" approaches for accessing elaborate HNCs by control of interfacial lattice strain and surface energy in liq. media. Various topol. configurations were analyzed, including concentric core/shell architectures, hetero-oligomers grouping spherical material domains, and more asym. hybrid nanostructures based on rod-shaped sections. The chem.-phys. properties and technol. advantages offered by such multifunctional HNCs are also summarized.
176 citations
TL;DR: In this paper, a new metal-organic framework with amino groups situated inside the pores has been synthesized, which has been modified by post-synthesis with two different functionalities, showing that it is possible to transform the cavities of a MOF without modifying its original 3D structure.
Abstract: A new metal–organic framework (MOF) with amino groups situated inside the pores has been synthesized. This MOF has been modified by post-synthesis with two different functionalities. The crystal structures of the two functionalized MOFs clearly demonstrate that it is possible to transform the cavities of a MOF without modifying its original 3D structure. These unprecedented results open up tremendous possibilities in the field of MOF chemistry because many potential applications in the fields of catalysis, material science or nanochemistry can be envisaged when applying the reported synthetic pathway.
169 citations
TL;DR: The current state of the chemistry of mono-and bidentate N-heterocyclic germylenes, stannylenes, plumbylenes and related compounds is reviewed with special emphasis placed on benzannulated derivatives.
Abstract: The current state of the chemistry of mono- and bidentate N-heterocyclic germylenes, stannylenes, plumbylenes, and related compounds is reviewed with special emphasis placed on benzannulated derivatives. The preparation, electronic structure, aggregation behaviour, and the coordination chemistry of the free benzannulated carbene analogues and their adducts with Lewis bases and complexes with transition metals are discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
167 citations
TL;DR: A summary of the relatively large body of research on the preparation and sensing properties of ferrocenes containing nitrogen functionalities, which have been mainly developed by our research group is provided in this paper.
Abstract: This manuscript provides a summary of the relatively large body of research on the preparation and sensing properties of ferrocenes containing nitrogen functionalities, which have been mainly developed by our research group. After a general overview of the topic, selected recent advances in this field are described. In particular, new acyclic and cyclic structural motifs, in which the ferrocene unit is linked by unsaturated aza bridges (azadiene, azine, urea, guanidine, azaheterocycles) to a chromogenic or fluorescent signalling unit. Attention is drawn to the electrochemical and optical properties of these aza-substituted ferrocene derivatives as well as their use in multichannel molecular recognition processes towards metal cations and anions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
163 citations
TL;DR: In this article, a review describes the recent advances made in the syntheses, structures (including the use of synchrotron sources and variable-temperature crystal structures and PXRD determinations of unit cell axes), magnetism, and photomagnetism of dinuclear and 1-D chain spin-crossover compounds of (primarily) iron(II), iron(III) and cobalt(II).
Abstract: This review describes the recent advances made in the syntheses, structures (including the use of synchrotron sources and variable-temperature crystal structures and PXRD determinations of unit cell axes), magnetism, and photomagnetism of dinuclear and 1-D chain spin-crossover compounds of (primarily) iron(II), iron(III) and cobalt(II). It focuses on the work of the author's group and also includes a discussion of related work by other groups. In particular, the early and ongoing work by Kahn, Real, Gutlich and co-workers on bipyrimidine-bridged FeII dinuclear materials has been extended by us and others to include many other new bridging and capping ligands. This had led to a fuller understanding of the spin transitions that involve HS-HS, HS-LS and LS-LS pair states. The same is being achieved for new 1-D chain materials, and notable advances include structural observation of ordered and disordered metal centres and corresponding spin states. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this paper, the coordination chemistry of neutral ambiphilic and amphoteric ligands is discussed, and various designs of molecules having both donor and acceptor moieties and strategies to prevent selfaggregation and favor transition-metal coordination are discussed.
Abstract: This review focuses on the coordination chemistry of neutral ambiphilic and amphoteric ligands. The various designs of molecules having both donor and acceptor moieties and the strategies to prevent self-aggregation and favour transition-metal coordination will be discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this article, the authors present a review of all reported systems that have the corresponding [Mn4O6] core, either in isolated complexes or in frameworks, and discuss the demonstrated and potential outcomes, in terms of physical properties, of such coordination assemblies of high-spin complexes.
Abstract: The synthesis of transition-metal high-spin complexes and of infinite coordination networks of these high-spin carriers now represents a recognized subdiscipline of coordination chemistry. This new research trend has been particularly encouraged by the discoveries that molecular and one-dimensional coordination aggregates may behave as nanomagnets, as illustrated by the so-called single-molecule magnets (SMMs) and single-chain magnets (SCMs). While the synthesis of isolated polynuclear high-spin complexes still rely mostly on serendipitous assembly with appropriate ligands, the synthesis of SCMs or extended networks of high-spin complexes demands a more designed and controlled bottomup assembly of precursor complexes and bridging species selected for their coordination abilities. In this context, the case of a [Mn4] SMM is unique in the literature, as one-, two-, and three-dimensional networks have been rationally designed by using this SMM unit as a building block, giving rise to original magnetic properties. This review gathers all reported systems that we know of, having the corresponding [Mn4O6] core, either in isolated complexes or in frameworks. Their structures and, when relevant, the synthetic strategy and magnetic properties are described. The demonstrated and potential outcomes, in terms of physical properties, of such coordination assemblies of high-spin complexes are then discussed. These are highlighted through examples with other building blocks, to broaden the scope of possible strategies and building blocks, and thus provide a basis for the further development of this promising area.
TL;DR: The use of metal-ion-mediated base pairs, i.e. the replacement of natural nucleobases by ligands, was suggested as an alternative means in this paper.
Abstract: Nucleic acids and their analogues raise more and more interest in research areas outside biology and biochemistry. The functionalization of these evolutionary optimized self-assembling macromolecules with metal ions widens their applicability even further. Previous efforts to incorporate metal ions site-specifically into nucleic acids focused on the covalent attachment of appropriate ligands to either the sugar phosphate backbone or the nucleobases. More recently, the use of metal-ion-mediated base pairs, i.e. the replacement of natural nucleobases by ligands, was suggested as an alternative means. This microreview discusses selected examples of metal-ion-mediated base pairs, including those that comprise unmodified natural nucleobases, and describes possible applications for the resulting metal-modified nucleic acids. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this article, Anderson-type polyoxomolybdates were functionalized with pendant pyridyl groups, and evidence for electronic communication between the polyoxometalate and the porphyrin was established by fluorescence spectroscopy.
Abstract: Two Anderson-type polyoxomolybdates [FeMo6O18{(OCH2)3CNHCO(4-C5H4N)}2]3– and [MnMo6O18{(OCH2)3CNHCO(4-C5H4N)}2]3– and two Lindqvist-type polyoxovanadates [V6O13{(OCH2)3CCH2OC(O)(4-C5H4N)}2]2– and [V6O13{(OCH2)3CNHCO(4-C5H4N)}2]2– were functionalized with pendant pyridyl groups. The electrochemical analysis revealed reversible redox processes at the heteroatom of the Anderson-type compounds and at the vanadium atoms in the Lindqvist series. Axial coordination of the polyoxometalate-grafted pyridyl groups to the metal ion in [Ru(CO)TPP] (TPP = tetraphenylporphyrin) and [ZnTPP] yielded polyoxometalate–porphyrin assemblies in solution. Evidence for electronic communication between the polyoxometalate and the porphyrin was established by fluorescence spectroscopy. Cyclic voltammetry showed the influence of the porphyrin on the redox process of the polyoxometalate and also nucleophilic attack at the porphyrin skeleton by the pendant pyridyl groups. Implications for the construction of supramolecular functional devices based on these components are discussed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this article, the single-crystal structure of [Au9(PPh3)8]-NO3)3 was resolved for the first time with atomic resolution.
Abstract: The single-crystal structure of [Au9(PPh3)8](NO3)3 was resolved for the first time with atomic resolution. The cluster has crystallographic D2 and approximate molecular D2h skeletal symmetry derived from an icosahedron. Voltammetry of the Au9 clusters in CH2Cl2 reveals a 1.78-eV energy gap between the first one-electron oxidation peak and the first reduction peak. The UV/Vis and luminescence properties of Au9 clusters were also investigated. The cluster solid shows two broad emission peaks at 579 nm and 853 nm, respectively, at room temperature. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: Two linear, trinuclear mixed-valence complexes, Co-II{(mu-L-1)(mu-OAc)Co-III (OAc)}(2)] and Co-III{L-3)(OAc)] were prepared and the molecular structures of 1, 2 and 4 elucidated on the basis of X-ray crystallography.
Abstract: Two linear, trinuclear mixed-valence complexes, [Co-II{(mu-L-1)(mu-OAc)Co-III (OAc)}(2)] (1) and [Co-II(mu-L-2) (mu-OAc)Co-III(OAc)}(2)] (2) and two mononuclear Con' complexes [Co-III{L-3)(OAc)] (3), and [Co-III {L-4}(OAc)] (4) were prepared and the molecular structures of 1, 2 and 4 elucidated on the basis of X-ray crystallography [OAc = Acetate ion, H2L1 = H(2)Salen 1,6-bis(2-hydroxyphenyl)-2,5-diazahexa-1,5-diene, H2L2 H2Me2-Salen = 2,7-bis(2-hydroxyphenyl)-2,6-diazaocta-2,6-diene, H2L3 = H(2)Salpn = 1,7-bis(2-hydroxyphenyl)-2,6-diazahepta1,6-diene, H2L4 = H(2)Me(2)Salpn = 2,8-bis(2-hydroxyphenyl)3,7-diazanona-2,7-dienel In complexes I and 2, the acetate groups show both monodentate and bridging bidentate coordination modes, whereas chelating bidentate acetate is present in 4 The terminal (CoN2O4)-N-III centres in 1 and 2 exhibit uniform facial arrangements of both non-bridged N2O and bridging O-3 donor sets and the Co-II centre is coordinated to six (four phenoxo and two acetato) oxygen atoms of the bridging ligands The effective magnetic moment at room temperature corresponds to the presence of high-spin Coll in both 1 and 2 The complexes 1 and 2 are thus Co-III(S = 0)Co-II(S = 3/2)-Co-II(S = 0) trimers Complexes 3 and 4 are monomeric and diamagnetic containing low-spin Co-III(S = 0) with chelating tetradentate Schiff base and bidentate acetate Calculations based on DFT rationalise the formation of trinuclear or monomiclear complexes (C) Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this article, single-crystal Xray diffraction and vibrational spectroscopy of NaBH4·2H2O and NaBh4 were studied.
Abstract: NaBH4·2H2O and NaBH4 were studied by single-crystal Xray diffraction and vibrational spectroscopy. In NaBH 4·2H2O, the BH4 - anion has a nearly ideal tetrahedral geometry and is bridged with two Na+ ions through the tetrahedral edges. The structure does not contain classical hydrogen bonds, but reveals strong dihydrogen bonds of 1.77-1.95 A. Crystal structures and vibrational spectra of NaBr·2H2O and NaBH 4·2H2O reveal many similarities. The unit cell volume of NaBH4·2H2O increases linearly with temperature between 200 and 313 K. At 313-315 K, the hydrate decomposes into NaBH4 and H2O, which react to release hydrogen. © Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
TL;DR: In this paper, the chemistry of coinage-metal-ethylene adducts that have been synthesized and characterized by X-ray crystallography is discussed, and bidentate and tridentate donors based on nitrogen appear to be the ligands of choice for stabilizing species with an M-C2H4 (M = CuI, AgI, and AuI) moiety.
Abstract: Despite the interest in them, easily isolable and thermally stable CuI, AgI, and AuI complexes of ethylene are stilllimited and get increasingly sparse as one descends the group 11 triad towards gold. Recently, there have been some notable developments in this field, including the isolation of gold–ethylene complexes and coinage-metal adducts with more than one ethylene molecule on a metal center. This article focuses on the chemistry of coinage-metal–ethylene adducts that have been synthesized and characterized by X-ray crystallography. Thus far, bidentate and tridentate donors based on nitrogen appear to be the ligands of choice forstabilizing species with an M–C2H4 (M = CuI, AgI, and AuI) moiety. Weakly donating ligands and anions are also commonly used, as they do not interfere with and displace the ethylene from the metal center. The ethylene 13C NMR chemical shift provides useful information about the nature of the metal–ethylene interaction. In some adducts (especially those with relatively weak M–C2H4 interactions), the change in the C=C bond length upon coordination to the metal site is difficult to discern because it falls within the errors associated with the crystallographically determined C=C bond length value. IR and Raman C=C stretching data would be useful but, probably due to the very weak nature of the IR band and the lack of convenient access to the Raman instruments, are often not reported. In this microreview, results from some computational and gas-phase spectroscopic studies are also provided for comparison.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this paper, the principle of Forster resonance energy transfer (FRET) occurring between closely spaced energy-donor and -acceptor molecules is described in relation with the data extractable from spectroscopic measurements.
Abstract: In this microreview we describe the principle of Forster resonance energy transfer (FRET) occurring between closely spaced energy-donor and -acceptor molecules. The theoretical treatment is depicted in relation with the data extractable from spectroscopic measurements. We present the specific case of semiconductor nanocrystals (or quantum dots – QDs) as energy donors in FRET experiments and a particular emphasis is put on the specific advantages of these fluorophores with regard to both their exceptional photophysical properties and their nanoscopic morphology. In a following section, the special attributes of luminescent lanthanide complexes
TL;DR: In this article, an overview of metal-based metallo-receptors can be found, which combine the structural and functional properties of metal centres with the recognition capabilities of organic ligands to selectively bind anionic guests.
Abstract: The selective recognition of anionic species by molecular receptors is an area of increasing interest due to the important roles played by anions in biological systems and the environment. An attractive approach for the recognition of anions is to use metal-based receptors, which provides some important advantages over purely organic hosts. Metallo-hosts can combine the structural and functional properties of metal centres with the recognition capabilities of organic ligands to selectively bind anionic guests. In our group we have developed different approaches for the synthesis of this type of metallo-receptors. One of these approaches is based on the use of the anion of interest as a templating agent to link together different organic and metal-containing building blocks into assemblies that have high selectivity for the templating anion. This microreview aims to give an overview of the research carried out in the author's group in this area over the past few years. Relevant examples from other groups are discussed and, where appropriate, compared to the work carried out in our group.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this paper, the development of novel ruthenium complexes displaying high performance in the catalytic asymmetric transfer hydrogenation of ketones with 2-propanol, providing this procedure alternative to the hydrogenation with dihydrogen.
Abstract: This Microreview focuses on the development of novel ruthenium complexes displaying high performance in the catalytic asymmetric transfer hydrogenation of ketones with 2-propanol, providing this procedure alternative to the hydrogenation with dihydrogen. The key role is played by 1-(pyridin-2-yl)methanamine (Pyme) type ligands which in combination with appropriate phosphanes afforded ruthenium systems of unprecedented high catalytic activity and productivity for the reduction of ketones and aldehydes. For the pincer CNN complexes a mixed inner-outer sphere mechanism involving Ru-hydride and Ru-alkoxide species is proposed. The excellent properties of these complexes are expected to have implications for the design of a new generation of catalysts.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this article, a series of β-diketonate, keto(aryl)iminato, and β-bis (aryl) iminato complexes of difluoroboron, twenty in total, have been prepared to assess the impact of chelate ring and aniline substitution on the structural, electrochemical, and photophysical properties of these ubiquitous chelates.
Abstract: A series of β-diketonate, keto(aryl)iminato, and β-bis(aryl)iminato complexes of difluoroboron, twenty in total, have been prepared to assess the impact of chelate ring and aniline substitution on the structural, electrochemical, and photophysical properties of these ubiquitous chelates. DFT (B3LYP/6-31G*) calculations supplemented the experimental results and both demonstrated that replacing oxygen with the more electron-donating aniline groups serves to only fine-tune the electronic properties because both the HOMO and LUMO energies are affected by such substitution. The electronic properties of all compounds are most greatly influenced by the nature of the substituents bound to the carbon portion of the chelate ring. Each difluoroboron complex undergoes two ligand-based, one-electron reductions where the first reduction potential becomes less favorable with increasing aniline substitution. Similarly, replacing oxygen with the more electron-donating aniline groups gives rise to slightly red-shifted absorption and emission processes. Substitution on the aniline ring has little, if any, influence on the electronic properties of the resultant complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this article, a concerted addition of silane to ketone through a six-coordinate hypervalent silicon intermediate is proposed, which does not involve addition of the calcium hydride to the ketone functionality.
Abstract: Reactions of the dimeric calcium hydride complex[(DIPP-nacnac)CaH·thf]2 {1; DIPP-nacnac = CH[(CMe)(2,6-iPr2C6H3N)]2} with the α-hydrogen containing ketones acetophenone, acetone, dibenzylketone and 2-adamantone are smooth. In most cases not only addition but also substantial enolization is observed as a side reaction and in some cases also aldol condensation was found. Despite this unselectivity, the addition products could be isolated crystalline pure. Crystal structures of [(DIPP-nacnac)CaOCH(Me)Ph]2 (3), [(DIPP-nacnac)CaOCH(CH2Ph)2]2 (6) and [(DIPP-nacnac)Ca(2-adamantoxide)]2 (7) have been determined. The calcium hydride complex 1 is an effective catalyst in the hydrosilylation of ketones. Independent from the silane/ketone ratio, a strong preference for formation of bis-alkoxy silanes [PhSiH(OR)2] is observed. In most cases no enoxy groups have been found in the product. This indicates that the mechanism does not involve addition of the calcium hydride to the ketone functionality. A concerted addition of silane to ketone through a six-coordinate hypervalent silicon intermediate is proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this article, the triazole-amine triazoles from click chemistry are convenient ligands for the formation of platinum complexes bearing combined triazola-amine or triazolara-carboxylate moieties and striking differences in the chelation modes are observed between the two series.
Abstract: Triazoles from “click chemistry” are convenient ligands for the formation of platinum complexes bearing combined triazole–amine or triazole–carboxylate moieties. Striking differences in the chelation modes are observed between the two series. One of the triazole–amine platinum complexes exhibits selective cytotoxicity against breast cancer cells lines. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: In this article, the design of ligand libraries of bidentate phosphorus ligands and the application of their transition-metal complexes in homogeneous (asymmetric) catalysis reactions are described.
Abstract: Combinatorial chemistry in combination with high-throughput screening technologies is an important way of finding new successful catalyst systems. The design of ligand libraries of bidentate phosphorus ligands and the application of their transition-metal complexes in homogeneous (asymmetric) catalysis reactions will be described in this review. Till now three different approaches were developed to arrive at such libraries of bidentate phosphorus ligands: 1) modular synthesis of bidentate ligands 2) the solid support synthesis of bidentate ligands and 3) the self-assembly of ligand building blocks into bidentate ligands. The scope and limitations of these strategies will be discussed on the basis of a limited number of articles that dealt with the synthesis of at least 15 bidentate phosphorus ligands.
TL;DR: The imidazolin-2-imino-functionalized tetramethylcyclopentadiene, 3-H, has been prepared by the reaction of two equivalents of 1,3-diisopropyl-4,5-dimethylimidazalin-2imine (1) with 5-(chlorodimethylsilyl)-1,2,3,4-tetramethyl-1,3 -cyclopentadienyl (2).
Abstract: The imidazolin-2-imino-functionalized tetramethylcyclopentadiene, 3-H, has been prepared by the reaction of two equivalents of 1,3-diisopropyl-4,5-dimethylimidazolin-2-imine (1) with 5-(chlorodimethylsilyl)-1,2,3,4-tetramethyl-1,3-cyclopentadiene (2). The reactions of 3-H with the trimethylsilylmethyl (neosilyl) [Ln(CH2SiMe3)3(THF)2] (Ln = Sc, Y, Lu) complexes afford tetramethylsilane and the constrained-geometry [(η5:η1-3)Ln(CH2SiMe3)2] (Ln = Sc, 4a; Ln = Y, 4b; Ln = Lu, 4c) complexes, whereas the analogousbis(trimethylsilyl)amido (HMDS) calcium complex, [(η5:η1-3)Ca(HMDS)(THF)] (5), can be obtained from 3-H and [Ca(HMDS)2(THF)2] with loss of hexamethyldisilazane, (Me3Si)2NH. The molecular structures of 4a–4c and 5 have been established by X-ray diffraction analyses, which confirm in all cases the formation of complexes with a chelating Me2Si-bridged cyclopentadienyl-imidazolin-2-imine ligand. The presence of short Ln–N and Ca–N bonds is indicative of the strong electron-donating capacity of the imidazolin-2-imino nitrogen atom, which is based on the ability of the imidazolium ring to effectively stabilize a positive charge. The rare earth metal complexes 4a–4c can be used as efficient catalysts for the hydroamination/cyclization reaction of terminal aminoalkenes and aminoalkynes.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: The water-soluble 2D Cu/Na coordination polymer [Cu(μ-dipic)2{Na2(μ -H2O)4}]n·2nH 2O (1) has been synthesized by self-assembly in aqueous medium from copper(II) nitrate, dipicolinic acid (H2dipric) and sodium hydroxide in the presence of triethanolamine as mentioned in this paper.
Abstract: The new water-soluble 2D Cu/Na coordination polymer [Cu(μ-dipic)2{Na2(μ-H2O)4}]n·2nH2O (1) has been synthesized by self-assembly in aqueous medium from copper(II) nitrate, dipicolinic acid (H2dipic) and sodium hydroxide in the presence of triethanolamine. It has been characterized by IR spectroscopy, FAB+-MS, elemental and single-crystal X-ray diffraction analyses, the latter featuring a layered 2D metal–organic structure that is extended to a 3D supramolecular assembly by extensive hydrogen bonding between adjacent layers and involving crystallization water molecules. Compound 1 has been shown to act as a catalyst precursor for the peroxidative oxidation of cyclohexane and cyclopentane to the corresponding cyclic ketones and alcohols by aqueous H2O2 in MeCN solution and in the absence of acid additives.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
TL;DR: A series of compds of general formula [Ru(.eta.6-p-cymene) (R2acac)(PTA)][X] have been prepd. and characterised spectroscopically as mentioned in this paper.
Abstract: A series of compds. of general formula [Ru(.eta.6-p-cymene) (R2acac)(PTA)][X] (R2acac = Me2acac, tBu2acac, Ph2acac, Me2acac-Cl; PTA = 1,3,5-triaza-7-phosphaadamantane; X = BPh4, BF4), and the precursor to the Me2acac-Cl deriv. [Ru(.eta.6-p-cymene)(Me2acac-Cl)Cl], have been prepd. and characterised spectroscopically. Five of the compds. have also been characterised in the solid state by X-ray crystallog. The tetrafluoroborate salts are water-sol., quite resistant to hydrolysis, and have been evaluated for cytotoxicity against A549 lung carcinoma and A2780 human ovarian cancer cells. The compds. are cytotoxic towards the latter cell line, and relative activities are discussed in terms of hydrolysis (less important) and lipophilicity, which appears to exert the dominating influence.
TL;DR: Tetranuclear lanthanide aqua hydroxo complexes with two structural types of core were prepared by heating (130 °C) of aqueous solutions of lanthanides(III) chlorides, cucurbit[6]uril (C36H36N24O12, CB[6]), and 4-cyanopyridine as discussed by the authors.
Abstract: Tetranuclear lanthanide aqua hydroxo complexes with two structural types of core – {Ln4(μ3-OH)4(μ2-OH)4}4+ [Ln = Pr (1), Nd (2), Eu (3), Gd (4), Tb (5)] and {Ln4(μ3-OH)4(μ2-OH)2}6+ [Ln = Er (6), Yb (7)] – were prepared by heating (130 °C) of aqueous solutions of lanthanide(III) chlorides, cucurbit[6]uril (C36H36N24O12, CB[6]), and 4-cyanopyridine The formation of Ln4 complexes results from the combined influence of the tetradentate coordination of the polycation by the portals of the macrocyclic ligand CB[6] and the chelating effect of the carboxylate ligands of isonicotinic acid generated as a result of hydrolysis of 4-cyanopyridine X-ray diffraction analysis of 1–7 revealed the sandwich structure with the tetranuclear lanthanide complex situated between two macrocyclic molecules The compounds were characterized by elemental analysis, IR, and electrospray ionization (ESI) mass spectrometry Luminescence spectra of 3 and 5 and magnetic properties of 4 were also studied(© Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2008)