Gang Lu

Chinese Academy of Sciences, Peping, Beijing, China

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Publications (30)148.86 Total impact

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    ABSTRACT: Cu-based nanocatalysts have been widely used for CO2 hydrogenation, but the poor stability is the bottleneck for further industrial application. A high-performance and long-lived Cu/SiO2 nanocatalyst was synthesized by ammonia-evaporation method for CO2 hydrogenation. The conversion of CO2 reaches up to 28%, which is close to the equilibrium conversion of CO2 (30%), and the selectivity to methanol is 21.3%, which is much higher than the equilibrium selectivity (6.9%) at 320 °C and 3.0 MPa. Furthermore, after 120 h evaluation the conversion can still maintain at a high value (27%), which is much better than Cu/SiO2 catalyst prepared by traditional impregnation. The Cu+ species has been demonstrated to be the active component for the activation and conversion of CO2. The higher ratio of Cu+/(Cu0 + Cu+) and interaction between metal and support deriving from copper phyllosilicate are mainly responsible for the high catalytic activity and excellent stability, respectively.
    No preview · Article · Jun 2015 · ACS Catalysis
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    Full-text · Dataset · Mar 2015
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    ABSTRACT: Pd/MgO catalysts are found, for the first time, to be extraordinarily active and stable for CO oxidative coupling to dimethyl oxalate. A series of Pd/MgO catalysts with Pd loadings of 0.1, 0.3, 0.5, 1 and 2 wt% were prepared by a wet impregnation method and systematically characterized by XRD, TEM, ICP, UV-DRS, H2-TPR and CO2-TPD. It has been demonstrated that the amount of Pd loading has a pronounced effect on the catalytic activity for CO oxidative coupling to dimethyl oxalate. CO conversion increases with the increase of the Pd loading due to high dispersion and similar sizes of Pd nanoparticles, as well as, the increase in number of surface active sites.
    No preview · Article · Jul 2014 · Catalysis Science & Technology
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    ABSTRACT: The rational design and synthesis of ternary two-dimensional alloy nanocrystals with a non-layered structure are still a challenge. Here, we show, for the first time, the synthesis of homogeneous ternary ZnS1−xSex nanosheets by thermal decomposition of lamellar inorganic-organic hybrid precursors. The morphology, composition and crystal structure of ZnS1−xSex nanosheets have been thoroughly investigated. We also found that the lattice constants and bandgaps of ZnS1−xSex nanosheets could be easily tuned via alteration of the Se/S ratio. Our work provides a facile and effective strategy to synthesize homogeneous multinary non-layered chalcogenide nanosheets with tunable compositions and bandgaps.
    No preview · Article · Jun 2014 · CrystEngComm
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    ABSTRACT: Two new member of (V)(2n+2)/2[Bi2nCl8n+2] series hybrids, (BzV)2[Bi2Cl10] (1) and (BzV)5[Bi3Cl14]2·(C6H5CH2)2O (2) (where BzV(2+) = N,N'-dibenzyl-4,4'-bipyridinium and (C6H5CH2)2O = dibenzyl ether) have been obtained, and compound 2 contains an unprecedented discrete trimer [Bi3Cl14](5-) counterion. The novel in situ-synthesized symmetric viologen cation with aromatic groups on both sides of 4,4'-bipy would provide more opportunities to create π···π interactions to optimize the photochromic property of the hybrid, and different bismuthated-halide oligomers enable us to discuss the size effect in this series of compounds. Both 1 and 2 are photochromic, and their photoresponsive rate is faster than that of reported viologen-metal halide hybrids. Experimental and theoretical data illustrated that the size of the inorganic oligomer can significantly influence the photoresponsive rate of the viologen dication, and the π···π interaction behaves as not only a powerful factor to stabilize the viologen monocation radical but also the second electron-transfer pathway, from a π-conjugated substituent to a viologen cation, for the photochromic process.
    Full-text · Article · May 2014 · Inorganic Chemistry
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    ABSTRACT: The experimentally observed planar hypercoordinate carbon species were detected in gas phase experiments and characterized by photoelectron spectroscopy. According to the Boltzmann distribution law, the thermodynamically favorable isomers, especially global minima, were relatively easier to detect than other isomers in such an experimental process. Here, we reported a thermodynamically unfavorable case, i.e., D3h CN3Mg3(+) (1a), which we think is experimentally viable because all isomers that are energetically lower than 1a show bimolecular assembly type structures consisting of an N2 unit and various types of CNMg3(+) units. The natural bond orbital (NBO) analysis suggests that the bonding between N2 and CNMg3(+) is rather weak, and we think it is very hard to retain their basic structures when kinetic factors are considered. Consistently, the four lowest isomers in the second group show dissociation (to free N2 molecule and CNMg3(+) cations) during Born-Oppenheimer molecular dynamic (BOMD) simulations. In contrast, the structure of 1a can be maintained under temperatures up to 2000 K during the BOMD simulation, and ring-opening reaction studies suggest the barrier to be very high, 46.75 kcal/mol. We think the excellent kinetic stability of 1a will compensate for its thermodynamic instability and it will own its existence in the gas phase synthesis. Although many isomers in the second group are energetically more favorable than 1a, they will be dissociated by the kinetic process. In the magnetic field, the positively charged CNMg3(+) units will be separated quickly from N2 molecules in the general gas phase synthesis, and they are therefore undetectable.
    No preview · Article · Apr 2014 · The Journal of Physical Chemistry A
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    ABSTRACT: We have studied the electron-transfer photochromism of the crystalline adducts of 4,4′-bipyridine (Bpy) and carboxylic acids and revealed the key structural parameters that decide whether the photochromism can happen for the first time. Experimental and theoretical analyses on nine known examples showed that the hydrogen bonds, instead of π–π stacking interactions, are the defining factor to the photochromism. Only the presence of N–H···O hydrogen bonds can fulfill the electron transfer from the carboxylate group to the Bpy part, although both the N···O separations of O–H···N and N–H···O hydrogen bonds are suitable for the so-called through-space electron transfer. These results can not only help to screen out the photochromic species from the known hundreds of Bpy–carboxylic acid adducts deposited in the Cambridge Crystallographic Data Centre (CCDC) database but also guide the design and syntheses of new adducts using diverse N-heterocyclic aromatic molecules and carboxylic acids.
    No preview · Article · Apr 2014 · Crystal Growth & Design
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    ABSTRACT: Clean gold surface is inactive toward H2, however, computations, aided by experiments, reveal that gold surface could serve as a Lewis acid coupling with Lewis bases (e.g. imine and nitrile) to construct effective frustrated Lewis pairs (FLPs) to activate H2 and subsequently to achieve hydrogenation of small imines and nitriles. The Lewis base-coupled Au FLPs avoid tight adsorption of Lewis bases to gold surface via repulsion between nitrogen lone pair and the filled d-band electrons of the gold surface. This is different from the normal FLPs that use sterically demanding groups or a molecular scaffold to prevent formation of stable Lewis acid-base complexes. The enhanced reactivity of the gold surface toward H2 is due to the synergetic catalytic effects of Lewis acid (Au surface) and the coupled Lewis base (imine or nitrile), which is supported by projected density of states (PDOS) analyses. Among Cu, Ag and Au surfaces, Au surface exhibits such reactivity most significantly, because Au is much more electronegative than Cu and Ag. The study enriches the FLP chemistry by adding a new type (heterogeneous) of FLPs and reveals a new reaction mode for gold surface.
    No preview · Article · Mar 2014 · Chemical Science
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    ABSTRACT: Manipulating the degrees of concavity or Miller indices of high-index facets is significant for metal nanocrystals to further tailor their properties; however, generating a concave surface with negative curvature is still in the early development stage and tuning the degree of concavity remains a challenge. Herein, we have developed a simple and effective site-selective etching strategy to manipulate the concavity of rhodium (Rh) nanocrystals with high-index facets.
    Full-text · Article · Dec 2013 · Chemical Communications
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    ABSTRACT: M05-2X calculations have been applied to understand the reduction mechanism of CO2 to CH4 catalyzed by [TMPH]+[HB(C6F5)3]− (TMP = 2,2,6,6-tetramethylpiperidine) and B(C6F5)3 with silane ([Si]H) as the reductant. The CO2 activation proceeds via formation of an intermediate in which a HCOOH entity is well formed, followed by O−H bond breaking of the HCOOH entity to transfer Hδ− to TMP. Unlike the CO2 activation in the PCP-pincer nickel hydride ([Ni]H)- and N-heterocyclic carbene (NHC)-catalyzed CO2 conversion to methanol, the direct insertion of CO2 into the B−H bond of the catalyst is inoperative. The study elucidates why the present system can reduce CO2 to CH4, while the [Ni]H and NHC catalysts only can reduce CO2 to the methoxy level.
    No preview · Article · Oct 2013 · Inorganic Chemistry
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    ABSTRACT: Baby face: Interface engineering of ceria‐supported Au catalysts was achieved by a combination of DFT calculations and synthetic techniques. The reducibility of the Au/ceria catalysts was determined by the interfacial AuOCen structures.
    No preview · Article · Jun 2013 · ChemCatChem
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    ABSTRACT: A series of inorganic-organic hybrid compounds L(2)(Bi(2)Cl(10)) (L = HMV(2+) = N-proton-N'-methyl-4,4'-bipyridinium for 1, L = HBzV(2+) = N-proton-N'-benzyl-4,4'-bipyridinium for 2, and L = HPeV(2+) = N-proton-N'-phenethyl-4,4'-bipyridinium for 3) have been successfully synthesized by an in situ solvothermal reaction. Compounds 1-3, with the same metal halide as anions but different asymmetric viologen molecules as cations, are ideal model compounds for investigating the detailed effect of different photochromically active molecules on the photochromic properties of the hybrids. Compound 1 shows no photochromic behavior, but compounds 2 and 3 possess photochromism and show a faster photoresponse rate than other reported viologen metal halide hybrids. Studies on the relationship between the structure and photochromic behavior clearly reveal that π-conjugated substituents could be used to improve the photoresponsibility and enrich the developed color efficiently and that the π···π interaction among organic components may not only be a powerful factor to stabilize the viologen monocation radical but also act as the second path of electron transfer from the π-conjugated substituent to the viologen cation for the photochromic process, which significantly influences the photochromic properties.
    Full-text · Article · Jan 2013 · Inorganic Chemistry
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    ABSTRACT: Hydrogen activation is a key step in hydrogenation reactions which are widely used in both laboratory synthesis and the chemical industry. Traditionally, it was often considered that only transition metal complexes/systems are able to activate hydrogen and to catalyze hydrogenations. This view has been changed recently; more and more metal-free molecules/systems have been found capable of activating hydrogen. Among these developments, the frustrated Lewis pairs (FLPs) are of particular significance, not only because they exhibit high reactivity toward hydrogen as well as other small molecules, but also because some of them can perform direct catalytic hydrogenations, which pave the way to the development of cheaper and greener hydrogenation catalysts. Inspired by the FLP principle, we used quantum mechanics computations to design molecules for H(2), CH(4), and NH(3) activation and catalysts for hydrogenation of imines, ketones, and alkenes. While our designed molecules are awaiting experimental preparation, the active sites in our designed molecules anticipated the features appeared in the compounds synthesized later by experimentalists. This chapter reviews our computational explorations to enrich FLP chemistry.
    No preview · Article · Nov 2012 · Topics in current chemistry
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    ABSTRACT: Searches for planar hexacoordinate carbon (phC) species comprised of only seven atoms uncovered good CX3M3 prototypes, D3h CN3Be3+ and CO3Li3+. The latter is the global minimum. It might also be possible to detect the deep-lying kinetically-viable D3h CN3Be3+ local minimum, based on its robustness toward molecular dynamic simulations and its very high isomerization barrier.
    Full-text · Article · Oct 2012 · Physical Chemistry Chemical Physics
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    ABSTRACT: Searches for planar hexacoordinate carbon (phC) species comprised of only seven atoms uncovered good CX(3)M(3) prototypes, D(3h) CN(3)Be(3)(+) and CO(3)Li(3)(+). The latter is the global minimum. It might also be possible to detect the deep-lying kinetically-viable D(3h) CN(3)Be(3)(+) local minimum, based on its robustness toward molecular dynamic simulations and its very high isomerization barrier.
    No preview · Article · Jul 2012 · Physical Chemistry Chemical Physics
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    ABSTRACT: Frustrated Lewis pairs (FLPs) has been applied to catalytic metal-free hydrogenation. Can the FLP reactivity be used for catalytic hydroamination? Using density functional theory (DFT) calculations, we have explored whether the molecules cat1-cat3, which were previously designed by integrating the dearomatization-aromatization effect and the FLP reactivity, can catalyze the intramolecular hydroaminations of non-activated aminoalkenes to afford nitrogen heterocycles. The study shows that the γ-aminoalkene (am1) hydroamination catalyzed by cat1 proceeds via two steps (aminoalkene N-H bond activation and C-N bond formation) with experimentally accessible energetics, giving the five-membered nitrogen heterocycle product 1,1-dimethylpyrrolidine. The N-H bond activation is reversible. The C-N bond formation step undergoes a concerted mechanism and complies with the Markovnikov addition rule. Possible side reactions which may cause catalyst deactivation were confirmed to be energetically unfavorable. The molecules cat2 and cat3 are less effective than cat1 in catalyzing the am1 hydroamination, but the barriers are not too high. By following the most favorable pathway of the cat1-mediated am1 hydroamination, we further extended the substrate (am1) to other aminoalkenes, including the methyl and phenyl β-substituted am1 (i.e. am2 and am3, respectively), the benzyl-protected primary aminoalkene (am4), and the δ-aminoalkene (am5). The hydroaminations of am2 and am3 have energetics comparable with am1 hydroamination, the am5 hydroamination is energetically less favorable, and the am4 hydroamination is least favorable but could be realizable by elevating the temperature and pressure. We call experimental efforts to synthesize cat1-cat3 or similar new molecules on the basis of the design strategy.
    No preview · Article · May 2012 · Dalton Transactions
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    ABSTRACT: Despite their formal relationship to alkynes, Ar'GeGeAr', Ar'SnSnAr', and Ar*SnSnAr* [Ar' = 2,6-(2,6-iPr(2)C(6)H(3))(2)C(6)H(3); Ar* = 2,6-(2,4,6-iPr(3)C(6)H(2))(2)-3,5-iPr(2)C(6)H] exhibit high reactivity toward H(2), quite unlike acetylenes. Remarkably, the products are totally different. Ar'GeGeAr' can react with 1-3 equiv of H(2) to give mixtures of Ar'HGeGeHAr', Ar'H(2)GeGeH(2)Ar', and Ar'GeH(3). In contrast, Ar'SnSnAr' and Ar*SnSnAr* react with only 1 equiv of H(2) but give different types of products, Ar'Sn(μ-H)(2)SnAr' and Ar*SnSnH(2)Ar*, respectively. In this work, this disparate behavior toward H(2) has been elucidated by TPSSTPSS DFT computations of the detailed reaction mechanisms, which provide insight into the different pathways involved. Ar'GeGeAr' reacts with H(2) via three sequential steps: H(2) addition to Ar'GeGeAr' to give singly H-bridged Ar'Ge(μ-H)GeHAr'; isomerization of the latter to the more reactive Ge(II) hydride Ar'GeGeH(2)Ar'; and finally, addition of another H(2) to the hydride, either at a single Ge site, giving Ar'H(2)GeGeH(2)Ar', or at a Ge-Ge joint site, affording Ar'GeH(3) + Ar'HGe:. Alternatively, Ar'Ge(μ-H)GeHAr' also can isomerize into the kinetically stable Ar'HGeGeHAr', which cannot react with H(2) directly but can be transformed to the reactive Ar'GeGeH(2)Ar'. The activation of H(2) by Ar'SnSnAr' is similar to that by Ar'GeGeAr'. The resulting singly H-bridged Ar'Sn(μ-H)SnHAr' then isomerizes into Ar'HSnSnHAr'. The subsequent facile dissociation of the latter gives two Ar'HSn: species, which then reassemble into the experimental product Ar'Sn(μ-H)(2)SnAr'. The reaction of Ar*SnSnAr* with H(2) forms in the kinetically and thermodynamically more stable Ar*SnSnH(2)Ar* product rather than Ar*Sn(μ-H)(2)SnAr*. The computed mechanisms successfully rationalize all of the known experimental differences among these reactions and yield the following insights into the behavior of the Ge and Sn species: (I) The active sites of Ar'EEAr' (E = Ge, Sn) involve both E atoms, and the products with H(2) are the singly H-bridged Ar'E(μ-H)EHAr' species rather than Ar'HEEHAr' or Ar'EEH(2)Ar'. (II) The heavier alkene congeners Ar'HEEHAr' (E = Ge, Sn) cannot activate H(2) directly. Instead, Ar'HGeGeHAr' must first isomerize into the more reactive Ar'GeGeH(2)Ar'. Interestingly, the subsequent H(2) activation by Ar'GeGeH(2)Ar' can take place on either a single Ge site or a joint Ge-Ge site, but Ar'SnSnH(2)Ar' is not reactive toward H(2). The higher reactivity of Ar'GeGeH(2)Ar' in comparison with Ar'SnSnH(2)Ar' is due to the tendency of group 14 elements lower in the periodic table to have more stable lone pairs (i.e., the inert pair effect) and is responsible for the differences between the reactions of Ar'EEAr' (E = Ge, Sn) with H(2). Similarly, the carbene-like Ar'HGe: is more reactive toward H(2) than is Ar'HSn:. (III) The doubly H-bridged Ar'E(μ-H)(2)EAr' (E = Ge, Sn) species are not reactive toward H(2).
    No preview · Article · Apr 2012 · Journal of the American Chemical Society
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    ABSTRACT: Metal-free hydrogenation has been proposed to be a green alternative to the conventional hydrogenation mediated by precious transition metal complexes. Thanks to the discovery of FLP (frustrated Lewis pair) chemistry, the field has recently witnessed significant progress. Inspired by the FLP idea of synergically utilizing the catalytic effects of Lewis acid and base, we previously proposed a strategy to construct metal-free active sites for H(2) activation and designed a metal-free molecule (1) that shows high reactivity toward H(2). Encouraged by the recent experimental successes in applying the strategy, we have computationally explored if 1 can go further to serve as a catalyst to promote the hydrogenations of various unsaturated compounds examined by ethylene (CH(2)=CH(2) (4)), silyl enol ether (CH(2)=C(Me)OSiMe(3) (5)), imines (Me(2)C=NMe (6) and Ph(Me)C=NMe (7)), and ketone (Ph(Me)C=O (9)). The energetic results predicted at the M05-2X(IEFPCM, solvent = THF)/6-311++G** level indicate that these reactions have feasible kinetics and thermodynamics for experimental realization. The hydride transfer step follows the concerted mechanism, although the transfer process has asynchronous character for silyl enol ether (5) and imines (6 and 7). In addition, we have investigated the binding of CO(2) to 1 and the 1-mediated hydrogenation of CO(2).
    No preview · Article · Mar 2012 · Dalton Transactions
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    ABSTRACT: Development of efficient dehydrogenation/hydrogenation is critical to the realization of organic hydride hydrogen storage. Using B3LYP DFT calculations, we have investigated the catalytic mechanisms of the reversible 3qu4h/4qu dehydrogenation/hydrogenation (3qu4h = tetrahydroquinoline and 4qu = quinoline) catalyzed by the Ir-complex 2cat (Cp*IrPYD′, Cp* = η5-C5Me5 and PYD′ = CF3-substituted 2-pyridonate), reported by Yamaguchi and Fujita et al. Two reactive species (7bif and 12hcl) are identified to play important roles in the catalytic system. The species (7bif) with bifunctional reactivity can be facilely obtained from 2cat by just rotating the PYD′ ligand, while 12hcl (Cp*IrHCl) is generated via HPYD′ ligand (HPYD′ = CF3-substituted 2-hydroxypyridine) dissociation after hydrogen transfer in dehydrogenation or hydrogen activation in hydrogenation. The species 7bif mediates dehydrogenation via a hydrogen transfer mechanism, which is more favorable than the β-H elimination (BETAHE) one, confirming our conclusion drawn in the study of alcohol dehydrogenation catalyzed by a similar catalyst. The 12hcl species combines the substrates (e.g., 4qu) to form a reactive pair that simultaneously possesses Lewis acidic and basic reactivity to activate H2 with a mechanism similar to the H2 activation by metal-free FLP (frustrated Lewis pair). The hydrogen activation by the pair gives an ion pair that undergoes hydride transfer to complete the hydrogenation. Because the dimer (Cp*IrHCl)2 itself does not show reactivity toward hydrogen activation but can be easily decomposed into the reactive monomer (12hcl), we reason the experimentally observed hydrogenation of 4qu by using the dimer (Cp*IrHCl)2 is mediated by the monomer (12hcl). The species 7bif and 12hcl catalyze both dehydrogenation and hydrogenation processes via microscopic reversibility; depending on the absence or presence of H2, the reaction moves toward dehydrogenation or hydrogenation, respectively. The complete 3qu4h/4qu dehydrogenation/hydrogenation requires an isomerization step through imine enamine tautomerization and disproportionation. The protonation required for the disproportionation can be mediated by the dihydro intermediate (9oh_h) of 7bif or the ion pair (the product of H2 activation catalyzed by 12hcl). The predicted mechanisms reasonably rationalize the experimental observations in the (3qu4h 4qu)/2cat system.
    No preview · Article · May 2011 · Organometallics
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    ABSTRACT: There has been an increasing interest in developing efficient AAD (acceptorless alcohol dehydrogenation) catalysts, because of their potential applications in atom economic synthesis, H2 production from biomass or its fermentation products (mainly alcohols), and the development of organic hydride hydrogen storage systems. Using B3LYP DFT calculations with solvation effects accounted by the SMD solvent model, we have investigated the catalytic mechanism of a novel Ir catalyst (2cat) in the dehydrogenation of 1-phenylethanol (3ol). This study allows us not only to detail the β-H elimination (BETAHE) pathway proposed by the experimentalists but also to characterize a new pathway called the ligand rotation-promoted hydrogen transfer (LRPHT) pathway. Combining the predicted energetics and experimental results/observations, we confirmed that the LRPHT pathway is more favorable than the BETAHE pathway in 3ol/2cat. According to the favorable LRPHT pathway, we show that the facile ligand rotation between the 18e2cat complex and the 16e bifunctional reactive species 7bif is responsible for the novelty of the catalyst. The bifunctional reactivity of the species makes the hydrogen transfer feasible for dehydrogenation. The facile ligand rotation is also the reason that the dehydrogenation could be run under neutral conditions, because this activation mode does not require acidic/basic reaction conditions or acid/base promoters to activate the catalyst. Unveiling these characteristics of the new catalyst could aid the advancement of the experimental idea from the perspective of activating catalysts to generate a bifunctional active site via “ligand rotation”. We also studied the formation mechanism of the experimentally identified complexes, according to which various experimental observations were rationalized.
    No preview · Article · Mar 2011 · Organometallics