The conversion of an azacalixpyridine-supported Mo(0) tricarbonyl into a Mo(VI) trioxo complex with dioxygen (O2) is investigated in homogeneous solution and in a molecular film adsorbed on Au(111) using a variety of spectroscopic and analytical methods. These studies in particular show that the dome-shaped carbonyl complex adsorbed on the metal surface has the ability to bind and activate gaseous oxygen, overcoming the so-called surface trans-effect. Furthermore, the rate of the conversion dramatically increases by irradiation with light. This observation is explained with the help of complementary DFT calculations and attributed to two different pathways, a thermal and a photochemical one. Based on the experimental and theoretical findings, a molecular mechanism for the conversion of the carbonyl to the oxo complex is derived. This study describes the investigation of the conversion of an azacalixpyridine-supported Mo(0)-tricarbonyl into a Mo(VI)-trioxo complex with dioxygen (O2) in detail with different spectroscopic and analytical methods. The reaction takes place in solution, in solid state and as well on noble metal surface and is accelerated by exposure to light. The experimentally findings can be explained by DFT calculation and in sum a reaction mechanism is derived. image

Synthesizing intermetallic phases containing noble metals often poses a challenge as the melting points of noble metals often exceed the boiling point of bismuth (1560 °C). Reactions in the solid state generally circumvent this issue but are extremely time consuming. A convenient method to overcome these obstacles is the co-reduction of metal salts in polyols, which can be performed within hours at moderate temperatures and even allows access to metastable phases. However, little attention has been paid to the formation mechanisms of intermetallic particles in polyol reductions. Identifying crucial reaction parameters and finding patterns are key factors to enable targeted syntheses and product design. Here, we chose metastable γ-BiPd as an example to investigate the formation mechanism from mixtures of metal salts in ethylene glycol and to determine critical factors for phase formation. The reaction was also monitored by in situ X-ray diffraction using synchrotron radiation. Products, intermediates and solutions were characterized by (in situ) X-ray diffraction, electron microscopy, and UV-Vis spectroscopy. In the first step of the reaction, elemental palladium precipitates. Increasing temperature induces the reduction of bismuth cations and the subsequent rapid incorporation of bismuth into the palladium cores, yielding the γ-BiPd phase.

Molecular metal oxides often adopt common structural frameworks (i.e. archetypes), many of them boasting impressive structural robustness and stability. However, the ability to adapt and to undergo transformations between different structural archetypes is a desirable material design feature offering applicability in different environments. Using systems thinking approach that integrates synthetic, analytical and computational techniques, we explore the transformations governing the chemistry of polyoxovanadates (POVs) constructed of arsenate and vanadate building units. The water-soluble salt of the low nuclearity polyanion [V6As8O26](4-) can be effectively used for the synthesis of the larger spherical (i.e. kegginoidal) mixed-valent [V12As8O40](4-) precipitate, while the novel [V10As12O40](8-) POVs having tubular cyclic structures are another, well soluble product. Surprisingly, in contrast to the common observation that high-nuclearity polyoxometalate (POM) clusters are fragmented to form smaller moieties in solution, the low nuclearity [V6As8O26](4-) anion is in situ transformed into the higher nuclearity cluster anions. The obtained products support a conceptually new model that is outlined in this article and that describes a continuous evolution between spherical and cyclic POV assemblies. This new model represents a milestone on the way to rational and designable POV self-assemblies.

The synthesis of intermetallic phases formed from elements with very different melting points is often time and energy consuming, and in extreme cases the evaporation of a reactant may even prevent formation completely. An alternative, facile synthesis approach is the reduction of metal salts in the polyol process, which requires only moderate temperatures and short reaction times. In addition, the starting materials for this procedure are readily available and do not require any special treatment to remove or prevent passivation layers, for example. Although the formation of intermetallic particles via the polyol process is an established method, little attention has been paid to the mechanism behind it. However, it is precisely a deeper understanding of the underlying mechanisms that would enable better and more targeted synthesis planning and product design. Taking the well-known formation of Bi2Rh particles from Bi(NO3)3 and various rhodium salts in ethylene glycol as an example, we studied the chemical process in detail. We investigated the effects of anion type and pH on the polyol reaction. The reaction was also probed by in situ X-ray diffraction using synchrotron radiation. Products, intermediates and solutions were characterized by X-ray and electron diffraction, electron microscopy and optical spectroscopy. In the first step, co-reduction of the metal cations leads to BiRh. Only with increasing reaction temperature, the remaining bismuth cations in the solution are reduced and incorporated into the BiRh particles, leading to a gradual transition from BiRh to α-Bi2Rh.

The synthesis of intermetallic phases formed from elements with very different melting points is often time and energy consuming, and in extreme cases the evaporation of a reactant may even prevent formation completely. An alternative, facile synthesis approach is the reduction of metal salts in the polyol process, which requires only moderate temperatures and short reaction times. In addition, the starting materials for this procedure are readily available and do not require any special treatment to remove or prevent passivation layers, for example. Although the formation of intermetallic particles via the polyol process is an established method, little attention has been paid to the mechanism behind it. However, it is precisely a deeper understanding of the underlying mechanisms that would enable better and more targeted synthesis planning and product design. Taking the well-known formation of Bi2Rh particles from Bi(NO3)(3) and various rhodium salts in ethylene glycol as an example, we studied the chemical process in detail. We investigated the effects of anion type and pH on the polyol reaction. The reaction was also probed by in situ X-ray diffraction using synchrotron radiation. Products, intermediates and solutions were characterized by X-ray and electron diffraction, electron microscopy and optical spectroscopy. In the first step, co-reduction of the metal cations leads to BiRh. Only with increasing reaction temperature, the remaining bismuth cations in the solution are reduced and incorporated into the BiRh particles, leading to a gradual transition from BiRh to alpha-Bi2Rh.

Intermetallic phases are usually obtained by crystallization from the melt. However, phases containing elements with widely different melting and boiling points, as well as nanoparticles, which provide a high specific surface area, are hardly accessible via such a high-temperature process. The polyol process is one option to circumvent these obstacles by using a solution-based approach at moderate temperatures. In this study, the formation of Bi2Ir nanoparticles in a microwave-assisted polyol process was investigated. Solutions were analyzed using UV-Vis spectroscopy and the reaction was tracked with synchrotron-based in situ powder X-ray diffraction (PXRD). The products were characterized by PXRD and high-resolution transmission electron microscopy. Starting from Bi(NO3)3 and Ir(OAc)3, the new suboxide Bi4Ir2O forms as an intermediate phase at about 160 °C. Its structure was determined by a combination of PXRD and quantum-chemical calculations. Bi4Ir2O decomposes in vacuum at about 250 °C and is reduced to Bi2Ir by hydrogen at 150 °C. At about 240 °C, the polyol process leads to the immediate reduction of the two metal-containing precursors and crystallization of Bi2Ir nanoparticles.

The new transition-metal oxothiostannate [Ni(cyclen)(H2O)2]4[Sn10S20O4]·∼13H2O (1) was prepared under hydrothermal conditions using Na4SnS4·14H2O as the precursor in the presence of [Ni(cyclen)(H2O)2](ClO4)2·H2O. Compound 1 comprises the [Sn10S20O4]8- anion constructed by the T3-type supertetrahedron [Sn10S20] and the [Sn10O4] anti-T2 cluster. Channels host the H2O molecules, and the sample can be reversibly dehydrated and rehydrated without significantly affecting the crystallinity of the material. 119Sn NMR spectroscopy of an aqueous solution of Na4SnS4·14H2O evidences that between 25 and 120 °C only [SnS4]4- and [Sn2S6]4- anions are present. In further experiments, hints were found that the formation of tin oxosulfide ions depends on the Ni2+-centered complexes. Compound 1 exhibits promising photocatalytic properties for the visible-light-driven hydrogen evolution reaction, with 18.7 mmol·g-1 H2 being evolved after 3 h.

The new compound [Cu(cyclam)(H2O)]-{[Cu(cyclam)](2)[HTiNb9O28]}center dot 26H(2)O (1) (cyclam = 1,4,8,11-tetraazacyclotetradecane) was obtained under solvo-thermal conditions. Its crystal structure contains a monotitano-nonaniobate anion in which one position is equally occupied by Nb(V) and Ti(IV). The anions are expanded by [Cu(cyclam)](2+) cations via Nb-O-Cu bridges generating {[Cu(cyclam)](2)[HTiNb9O28]}(2-) cluster units, which are arranged into layers. Between these layers there are additionally isolated [Cu(cyclam)(H2O)(2)](2+) cations as well as hydrate water molecules. Storage of 1 at room temperature leads to loss of similar to 13 water molecules, and a new crystalline phase (2) crystallizes that, with heating, transforms into the anhydrate. The reversibility of this reaction was investigated by thermogravimetry and X-ray powder diffraction (XRPD). Temperature- dependent in situ synchrotron XRPD investigations prove an abrupt phase transition, in which especially the a axis is dramatically shortened and the {[Cu(cyclam)](2)[HTiNb9O28](2-)} cluster is rearranged. Single-crystal X-ray diffraction of 2 reveals that, despite the unusual large shrinking of the unit cell volume, the domains formed by water removal exhibit some preferred orientation close to that expected for a topotactic reaction, which allowed the performance of a structure analysis. In the structure of 2, the two water molecules of the isolated [Cu(cyclam)(H2O)](2+) cation in 1 are replaced by two terminal cluster O atoms, leading to the formation of chains via Nb-O-Cu bonds, and this phase transition is accompanied by an ordering of one of the two cyclam ligands.

[Bis(acetylacetonato)manganese(II)] complexes are important precursors for the synthesis of catalytic MnO nanoparticles. However, the mechanism of the formation of these materials still remains unknown. In this work, a combination of ex situ and synchrotron‐based in situ powder X‐ray diffraction with in situ pH, conductivity, and turbidity measurements was applied to investigate the concentration‐dependent formation of [Mn(acac)2(H2O)2]; interestingly [Mn(acac)2(H2O)2] undergoes an expansion of the unit cell during the synthesis as well as upon heating. Increasing the temperature to 80 °C caused the conversion of solid [Mn(acac)2(H2O)2] to the trimer compound [Mn(acac)2]3, which occurs ex situ (in solid state), but is hindered in solution. [Mn(acac)2(H2O)2] emits light in the blue‐green spectral range with emission maximum at 520 nm, measured in situ under real reaction conditions during its formation due to the instability of this compound.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

In situ investigations on the nucleation and crystallization processes are essential for understanding of the formation of solids. Hence, the results of such experiments are prerequisites for the rational synthesis of solid materials. The in situ approach allows the detection of precursors, intermediates, and/or polymorphs, which are mainly missed in applying ex situ experiments. With a newly developed crystallization cell, simultaneous in situ experiments with X-ray diffraction (XRD) and luminescence analysis are possible, also monitoring several other reaction parameters. Here, the crystallization of the model system tris(acetylacetonato)-aluminum(III) Al(acac)3 was investigated. In the time-resolved in situ XRD patterns, two polymorphs of Al(acac)3, the α- and the γ-phase, were detected at room temperature and the influence of the pH value onto the product formation was studied. Moreover, changes in the emission of Al(acac)3 and the light transmission of the solution facilitated monitoring the reaction by in situ luminescence. The first results demonstrate the potential of the cell to be advantageous for controlling and monitoring several reaction parameters during the crystallization process.

Applying a new synthesis protocol with cystamine dihydrochloride as sulfur source we were able to synthesize the new compound [La(dien)(3)](2)[Sn2S6]Cl-2 (1) (dien = diethylenetriamine) under solvothermal conditions. Under these conditions the S-S bond of the cystamine molecule is cleaved generating the S2- anions. The title compound is formed via an intermediate, (dienH)(2)Sn3S7, which reacts to the final product at longer reaction times. The structure crystallizes in the monoclinic space group P2(1)/n and is composed of two ninefold coordinated [La(dien)(3)](3+)complexes, one [Sn2S6](4-) anion, and two Cl- anions. The Hirshfeld surface analysis reveals a large number of intermolecular interactions including SH and ClH bonding.

Using the solvothermal approach five new tin-sulfur compounds were synthesized. All compounds exhibit a direct covalent bond between the thiostannate unit and the charge compensating transition metal TM2+ ion, leading to the formation of discrete neutral molecules, chains or layered structures. In the structures, the [Sn2S6]4– anion is connected to the TM2+ cations in three different ways: (a) only two and opposite terminal S atoms are involved in bonding; (b) the four terminal S atoms connect two different complexes, and (c) the four terminal S atoms link four complexes. The compounds are: {[Ni(phen)2]2[Sn2S6]}·biph (1), {[Ni(phen)2]2[Sn2S6]}·phen·H2O (2), {[Fe(1,2-dach)2][Sn2S6]}n·2n1,2-dachH (3), {[Ni(cyclam)]2[Sn2S6]}n·2nH2O (4), and {[Mn(2,2′-bipy)2]2[Sn2S6]} (5). Compounds 1–3 were prepared from elements/chlorides, whereas for the preparation of compounds 4 and 5 a new synthesis strategy was developed using Na4SnS4·14H2O and TM2+ centered complexes as precursor. Under solvothermal conditions in situ condensation reaction of the [SnS4]4– anions leads to the formation of the [Sn2S6]4– moiety.

The compound [Co4(C6H14N2)4(μ4-S2)2(μ2-S2)4] (I) and the pseudo-polymorph [Co4(C6H14N2)4(μ4-S2)2(μ2-S2)4]⋅4 H2O (II) were obtained under solvothermal conditions (C6H14N2=trans-1,2-diaminocyclohexane). The structures feature S2(2-) ions exhibiting two different coordination modes. Terminal S2(2-) entities join two Co(3+) centres in a μ2 fashion, whereas the central S2(2-) groups connect four Co(3+) cations in a μ4-coordination mode. Compound II can be transformed into compound I by heat and storage over P2O5 and storing compound I in humid air yields in the formation of compound II. The intermolecular interactions investigated through Hirshfeld surface analysis reveal that besides S⋅⋅⋅H bonding close contacts are associated with relatively weak H⋅⋅⋅H interactions. A detailed DFT analysis of the bonding situation explains the long S-S bonds in the μ4-bridging S2(2-) units and the short bonds for the S2(2-) moieties in the μ2-connecting mode. Photocatalytic hydrogen evolution experiments demonstrate the potential of compound II as catalyst.

During explorative solvothermal syntheses six new compounds containing either the [Sn2S6](4-) or the [SnS4](4-) anion were obtained and structurally characterized: [Ni(1,2-dach)(3)](2)Sn2S6 center dot 4H(2)O (1) (1,2-dach = trans-1,2-diaminocyclohexane), o-{[Ni(tepa)](2)Sn2S6} (2) (tepa = tetraethylenepentamine), [Ni(peha)](2)Sn2S6 center dot H2O (3) (peha = pentaethylenehexamine), [Ni(aepa)](2)Sn2S6 (4) (aepa = N-2-aminoethyl-1,3-propandiamine), [Co(dien)](2)Sn2S6 (5) (dien = diethylenetriamine), and {[Mn(trien)](2)SnS4} (trien = triethylenetetramine). In all compounds in-situ formed transition metal amine complexes act as charge compensating ligands or are bound to the thiostannate anions. Compound 2 is an orthorhombic polymorph of a recently published monoclinic compound. In compound 6 the very rare [Mn2N8S2] bi-octahedron is observed as main structural motif. This compound contains a one-dimensional chain which was also observed in a pseudo-polymorphic compound. The structures of all compounds are characterized by an extended hydrogen bonding network between S atoms of the anions and the H atoms of the amine ligands and/or water molecules. (C) 2014 Elsevier Masson SAS. All rights reserved.

AbstractThe structures of the new tin—sulfur containing compounds are determined by XRD.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

AbstractThe new compounds (II) and (IV) are solvothermally synthesized and their crystal structures are determined by single crystal XRD.

Zeitschrift für anorganische und allgemeine ChemieVolume 638, Issue 10 p. 1583-1583 Poster The New Thiostannate [Ni(aepa)2]2Sn2S6 Nicole Pienack, Nicole Pienack Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str. 2, 24118 Kiel, GermanySearch for more papers by this authorProf. Dr. Wolfgang Bensch, Corresponding Author Prof. Dr. Wolfgang Bensch wbensch@ac.uni-kiel.de Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str. 2, 24118 Kiel, GermanyInstitut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str. 2, 24118 Kiel, GermanySearch for more papers by this author Nicole Pienack, Nicole Pienack Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str. 2, 24118 Kiel, GermanySearch for more papers by this authorProf. Dr. Wolfgang Bensch, Corresponding Author Prof. Dr. Wolfgang Bensch wbensch@ac.uni-kiel.de Institut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str. 2, 24118 Kiel, GermanyInstitut für Anorganische Chemie, Christian-Albrechts-Universität zu Kiel, Max-Eyth-Str. 2, 24118 Kiel, GermanySearch for more papers by this author First published: 22 August 2012 https://doi.org/10.1002/zaac.201204034Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume638, Issue10August 2012Pages 1583-1583 RelatedInformation