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Polysiloxane-analogous Si–S compounds have so far not been reported. Transsilylation reactions of the solid pyridine adduct of HSiCl3 with gaseous Me3Si–S–SiMe3 yielded perhydridopolysilathianes. 29Si NMR, FTIR, and Raman spectroscopy; elemental and thermal analysis; XRD; SEM; and gas-adsorption measurements indicated that the product consists of D-, T-, and Q-units with a composition of ([H2SiS]1.2[HSiS1.5]2.6[SiS2]1.0)n. Formation of the latter is caused by pyridine-catalyzed dismutation reactions. The polymer is mesoporous with a surface area of 187 m2 g–1; furthermore, it is amorphous and insoluble in organic solvents.

The direct, catalytic, asymmetric α-functionalization of acyclic esters constitutes a significant challenge in the area of asymmetric catalysis, particularly where the configurational integrity of the products is problematic. Through the unprecedented merger of two independent, yet complementary, catalysis events it has been possible to facilitate the direct asymmetric α-allylation of readily available aryl acetic acid esters. Since enantioselection is determined by the nucleophile, this conceptual approach to cooperative catalysis constitutes a potentially general solution to the direct catalytic asymmetric α-functionalization of acyclic esters.

The metastable (at 25 °C) high-temperature phase of BaGe3 (tetragonal CaGe3-type structure, space group I4/mmm, Z = 8, powder XRD) is obtained by hot press sintering of arc melted precursor samples using 1% Ba excess for loss compensation (multi anvil press, 15 GPa, 1300 K).

Conspectus“Bare” metal–carbene complexes, when generated in the gas phase and exposed to thermal reactions under (near) single-collision conditions, exhibit rather unique reactivities in addition to the well-known metathesis and cyclopropanation processes. For example, at room temperature the unligated [AuCH2]+ complex brings about efficient C–C coupling with methane to produce C2Hx (x = 4, 6), and the couple [TaCH2]+/CO2 gives rise to the generation of the acetic acid equivalent CH2═C═O. Entirely unprecedented is the thermal extrusion of a carbon atom from halobenzenes (X = F, Cl, Br, I) by [MCH2]+ (M = La, Hf, Ta, W, Re, Os) and its coupling with the methylene ligand to deliver C2H2 and [M(X)(C5H5)]+. Among the many noteworthy C–N bond-forming processes, the formation of CH3NH2 from [RhCH2]+/NH3, the generation of CH2═NH2+ from [MCH2]+/NH3 (M = Pt, Au), and the production of [PtCH═NH2]+ from [PtCH2]+/NH3 are of particular interest. The latter species are likely to be involved as intermediates in the pla...

Novel tricyclic triazolopyridines were prepared in two steps from the requisite bicyclic 2-ketopyridines. In order to examine the scope of the process, a reliable route to the 2,3-dihydro-1,5-naphthyridin-4(1H)-one, 7,8-dihydro-5H-pyrido[3,2-b]azepin-9(6H)-one, 7,8-dihydrooxepino[3,2-b]pyridin-9(6H)-one, and 7,8-dihydro-5H-pyrido[3,2-c]azepin-9(6H)-one scaffolds was also established.

Although atomic force microscopy (AFM) was rapidly adopted as a routine surface imaging apparatus after its introduction in 1986, it has not been widely used in catalysis research. The reason is that common AFM operating modes do not provide the atomic resolution required to follow catalytic processes; rather the more complex noncontact (NC) mode is needed. Thus, scanning tunneling microscopy has been the principal tool for atomic scale catalysis research. In this Account, recent developments in NC-AFM will be presented that offer significant advantages for gaining a complete atomic level view of catalysis. The main advantage of NC-AFM is that the image contrast is due to the very short-range chemical forces that are of interest in catalysis. This motivated our development of 3D-AFM, a method that yields quantitative atomic resolution images of the potential energy surfaces that govern how molecules approach, stick, diffuse, and rebound from surfaces. A variation of 3D-AFM allows the determination of forces required to push atoms and molecules on surfaces, from which diffusion barriers and variations in adsorption strength may be obtained. Pushing molecules towards each other provides access to intermolecular interaction between reaction partners. Following reaction, NC-AFM with CO-terminated tips yields textbook images of intramolecular structure that can be used to identify reaction intermediates and products. Because NC-AFM and STM contrast mechanisms are distinct, combining the two methods can produce unique insight. It is demonstrated for surface-oxidized Cu(100) that simultaneous 3D-AFM/STM yields resolution of both the Cu and O atoms. Moreover, atomic defects in the Cu sublattice lead to variations in the reactivity of the neighboring O atoms. It is shown that NC-AFM also allows a straightforward imaging of work function variations which has been used to identify defect charge states on catalytic surfaces and to map charge transfer within an individual molecule. These advances highlight the potential for NC-AFM-based methods to become the cornerstone upon which a quantitative atomic scale view of each step of a catalytic process may be gained. Realizing this potential will rely on two breakthroughs: (1) development of robust methods for tip functionalization and (2) simplification of NC-AFM instrumentation and control schemes. Quartz force sensors may offer paths forward in both cases. They allow any material with an atomic asperity to be used as a tip, opening the door to a wide range of surface functionalization chemistry. In addition, they do not suffer from the instabilities that motivated the initial adoption of complex control strategies that are still used today.

Single phase Cs7[FeS2]2 [Fe2S3]2 is prepared by heating stoichiometric amounts of Cs2S2, Fe, and S under Ar (corundum crucible in steel autoclave, 800 or 1000 °C, 12 h).

With reference to the high-symmetric structure and significant stability of M@Au12 cage molecules (M = group 6 transition element), the geometric and electronic structures as well as bonding of various Sg@Au12 isomers are investigated by DFT (PW91, PBE, B3LYP) and wave function theory (MP2, CCSD(T)) approaches.

The hexagonal modification hP8 of EuGe3 is obtained by arc-melting of a stoichiometric mixture of the elements (1% excess of Eu) followed by high-pressure sintering (multianvil press, 12 GPa, 1100 K, 1 h).

Cs8[Fe4S10] (I) and Cs7[Fe4S8] (II) are prepared from stoichiometric samples of Fe, S, and Cs2S2 (corundum crucible in autoclave, ≤ 1070 K, 12 h).

The high-pressure modification of BaGe5 is obtained from a 1:5 molar mixture of Ba6Ge25 and Ba (multianvil press, 15 GPa, 1000-1200 K, 2 h).

The metastable title compounds are prepared from the elements at 1073 K and 15 GPa for BaGe6, and 10 GPa for BaGe6-x.

A synthetic strategy for previously unknown para-substituted N,N′-dihydroxybenzamidines and their O-monosubstituted and O,O′-disubstituted methyl, benzyl, and tetrahydropyranyl derivatives is described. The procedure starts with the corresponding hydroxamic acid chlorides, which after dehydrohalogenation give nitrile oxides. These intermediates in turn react with O-substituted hydroxylamines to afford the desired N,N′-dihydroxybenzamidines after workup. This new class of potential prodrugs was characterized by 15N NMR spectroscopy. The chemical shifts show significant correlations with Hammett σ values, especially for the oxime-type nitrogen with r2 > 0.99. The Hammett σ parameter reliably correlates with electron density in molecules. The presented results thus allow predictions relating to π-electron density and basicity in this functional group, and these are important parameters for the discussion of substrate enzyme interactions.

Cs11[Fe5S8]2[O] is prepared by heating a mixture of Fe, Cs2S2, and CsO2 or Fe2O3 as O source (corundum crucible, 1170 K, 12 h; cooling rate of 20 K/h).

A simple protocol is presented for the reaction of hydroxamic acid chlorides (I) with hydroxylamine (II).

Plate-shaped single crystals of tetragonal β-Fe1.00Se are grown from polycrystalline material by chemical vapor transport with AlCl3 as transport additive (evacuated quartz ampoule, temp.

Compounds (II), (IV), (VI), and (IX) are characterized by single crystal XRD and FP-LAPW band structure computations.

Orthorhombic o′-In2O3 (Rh2O3(II)-type, space group Pbcn, Z = 4) is synthesized in macroscopic quantities (ca. 10—100 mm3) from rhombohedral corundum-type rh-In2O3 at 8—9 GPa and 600—1100 °C in multianvil and toroid cell assemblies.

The title compounds BaIn3.1Hg3.9 (x = 3.1) (I) and BaInxHg11-x (x = 0—2.8) (II) are prepared from stoichiometric mixtures of the elements (Ta crucible, 825 K, cooling rate of 5 K/h).

The sulfidoferrates of title are prepared by solid state reaction of stoichiometric mixtures of Fe, S, K, and Rb2S (corundum crucible, K compounds: 900—1100°C, Rb compounds: 500—800°C, controlled heating).

The title compounds are prepared by high-pressure reaction of ζ-Fe2N (obtained from Fe and flowing NH3 at 708 K) and Ni or Co powder (15 GPa, 1473 K, 30 min).

The title compounds are prepared from Ln2X3 (Ln: Gd—Tm, X: S, Se) and sulfur or selenium (3 GPa, 1193—1973 K, 360—2600 min) and characterized by powder and single crystal XRD.

The new metastable title compounds are prepared by high pressure/high temperature reaction of the elements (Ta ampules, 12—15 GPa, 900—1400 K).

We present selected examples of gas-phase reactions which are of timely interest for the activation of small molecules. Due to the very nature of the experiments, detailed insight in the active site of catalysts is provided and—in combination with computational chemistry—mechanistic aspects of as well as the elementary steps involved in the making and breaking of chemical bonds are revealed.

The title compounds are prepared by thermal decomposition of the metastable phases LnGe5 (obtained by arc-melting of the elements at 923—1123 K and 8.3—9.5 GPa) at 543—573 K and ambient pressure for 2 h.

Chloroacetyl imides derived from chiral oxazolidinones react with cyanide to give the title compounds (III).

Hydrogen-atom transfer (HAT), as one of the fundamental reactions in chemistry, is investigated with state-of-the-art gas-phase experiments in conjunction with computational studies. The focus of this Minireview concerns the role that the intrinsic properties of gaseous oxo-clusters play to permit HAT reactivity from saturated hydrocarbons at ambient conditions. In addition, mechanistic implications are discussed which pertain to heterogeneous catalysis. From these combined experimental/computational studies, the crucial role of unpaired spin density at the abstracting atom becomes clear, in distinct contrast to recent conclusions derived from solution-phase experiments.

CaGe3 is synthesized by annealing mixtures of CaGe2 (obtained by reacting the elements in an arc furnace) and Ge at 10 GPa and 1200 K for 1 h.

Some arglabin derivatives with variations at the endo- or exocyclic double bond are synthesized and screened for their cytotoxicity.

“Rollover” cyclometalation constitutes a special case among the well-known class of cyclometalation reactions. An overview is given that covers the very first description of this reaction type, as well as recent developments. In addition, not only condensed-phase experiments are reviewed, but also investigations based on mass spectrometric techniques, together with “in silico” studies using DFT-based calculations are considered. While the latter two methods allow for a detailed analysis of the intrinsic factors that affect the reaction mechanisms, consideration of all three regimes permits to develop a coherent mechanistic picture and to address the often noted gap between condensed- and gas-phase studies. Moreover, the quite unexpected reactivity of “rollover” cyclometalated complexes in gas-phase experiments, as well as potential applications, e.g. in synthetic procedures, are discussed in some detail.

Mass-spectrometry-based experiments, complemented by computational studies, are presented which demonstrate the richness of nickel-containing reagents when employed in various bond-activation processes and conducted under single-collision conditions. We will address the chemistry of “naked” atomic Ni+, the dramatic effects of ligands L or of the size of clusters, which they exhibit in thermal reactions of NiL+ or Ni n + (n = 2–30). Special emphasis will be paid to identify elementary steps and to uncover mechanistic principles; as an example, various aspects of the face-selective dehydrogenation of cyclohexane by homo- and heteronuclear cluster-ion dimers are discussed in some detail for the first time.

Realgar, As(4)S(4), reacts with Cr(CO)(5)THF under cage degradation to give As(4)S(3)·Cr(CO)(5) (1). The reverse structural change is found if solutions of 1 in CH(2)Cl(2) react with equimolar amounts of PAs(3)S(3)·W(CO)(5) and CuX (X = Cl, Br, I) in CH(3)CN under biphasic diffusion conditions. The resulting coordination polymers 2-4 contain a reconstituted realgar molecule along with the PAs(3)S(3) cage. The crystal structures of (CuX)(As(4)S(4))(PAs(3)S(3)) (X = Cl: 2; Br: 3) are characterized by one-dimensional (1D) (CuX)(As(4)S(4)) strands, which are formed by alternating As(4)S(4) cages and CuX dumbbells. Terminal PAs(3)S(3) molecules are coordinated to copper by apical phosphorus and bridging realgar through sulfur. The As(3) triangles of the resulting (CuX)(As(4)S(4))(PAs(3)S(3)) strands interact with halides of neighbored strands to give a folded three-dimensional (3D) network. The structure of (CuI)(3)(As(4)S(4))(PAs(3)S(3)) (4) contains 1D (Cu(3)I(3))(n) strands as backbones, which are bridged by sulfur atoms of two η(1:2)-As(4)S(4) molecules while PAs(3)S(3) confines the resulting sheet. The As(3) triangles at the surface of the layers interact with iodide of the next layer to form a layered 3D network.