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Background: Intima proliferation and in-stent restenosis is a challenging situation in interventional treatment of small vessel obstruction. Al/Al 2 O 3 nanowires have been shown to accelerate vascular endothelial cell proliferation and migration in vitro, while suppressing vascular smooth muscle cell growth. Moreover, surface modification of Al/Al 2 O 3 nanowires with poly[bis(2,2,2-trifluoromethoxy)phosphazene (PTFEP) coating enables further advantages such as reduced platelet adhesion. Therefore, the study's goal was to compare the biocompatibility of novel Al/Al 2 O 3  + PTFEP coated nanowire bare-metal stents to uncoated control stents in vivo using optical coherence tomography (OCT), quantitative angiography and histomorphometric assessment., Methods: 15 Al/Al 2 O 3  + PTFEP coated and 19 control stents were implanted in the cervical arteries of 9 Aachen minipigs. After 90 days, in-stent stenosis, thrombogenicity, and inflammatory response were assessed. Scanning electron microscopy was used to analyse the stent surface., Results: OCT analysis revealed that neointimal proliferation in Al/Al 2 O 3  + PTFEP coated stents was significantly reduced compared to control stents. The neointimal area was 1.16 ± 0.77 mm 2 in Al/Al 2 O 3  + PTFEP coated stents vs. 1.98 ± 1.04 mm 2 in control stents (p = 0.004), and the neointimal thickness was 0.28 ± 0.20 vs. 0.47 ± 0.10 (p = 0.003). Quantitative angiography showed a tendency to less neointimal growth in coated stents. Histomorphometry showed no significant difference between the two groups and revealed an apparent inflammatory reaction surrounding the stent struts., Conclusions: At long-term follow-up, Al/Al 2 O 3  + PTFEP coated stents placed in peripheral arteries demonstrated good tolerance with no treatment-associated vascular obstruction and reduced in-stent restenosis in OCT. These preliminary in vivo findings indicate that Al/Al 2 O 3  + PTFEP coated nanowire stents may have translational potential to be used for the prevention of in-stent restenosis., Competing Interests: Declaration of competing interest The following co-authors hold a patent which is related to the contents of the manuscript: Ayman Haidar, Michael Veith, Cenk Aktas, Hashim Abdul-Khaliq, Ali Awadelkareem. Patent title: Beschichtung oder mit einer Beschichtung versehener Körper sowie Verfahren zu deren Herstellung. DAKZ 10 2017 113 7580. 2018; Deutsches Patent- und Markenamt. https://register.dpma.de/DPMAregister/pat/register?AKZ=1020171137580. In addition to this we declare that we have no conflicts of interest to disclose regarding this publication. If any conflicts of interest arise during the course of the publication, we will promptly disclose them to the editor of the publication or to the appropriate parties., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Currently, the largest (ramax = 19.9 Å) and by far the most complicated (234 atoms, C1 symmetry, 696 independent geometrical parameters, and 27 261 interatomic terms) experimental molecular structure of a cage-type Si6Tip6 (Tip = 2,4,6-iPr3C6H2) isomer has been investigated in the gas phase by the electron diffraction method (Tav = 645 K) supplemented with theoretical simulations. A detailed analysis of the current possibilities for experimentally investigating large molecular structures is performed. A series of density functional theory approximations and the role of dispersion interactions have been benchmarked using the obtained data. Based on the refined geometry of Si6Tip6, various quantum-chemical methods have been applied for the investigation of the electronic structure of its Si6 core. In particular, natural bond orbital, quantum theory of atoms in molecules, interacting quantum atoms, fractional occupation number weighted density, and complete active space self-consistent field (CASSCF) methods were utilized. The diradical character of the molecule has been assessed by the UHF and CASSCF approximations. The problem of bonding between the hemispheroidal silicon atoms has been investigated., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)

The core expansion of metallic or metalloid clusters by the addition of further homo- or heteronuclear vertices is pivotal to the nucleation and growth of particles. The exohedral grafting of a low-valent functionality followed by endohedral incorporation have been identified as key steps. Following previous work on the Si 6 series, we now report the synthesis and full characterization of the amidinatotetrylene-functionalized seven-vertex siliconoids Si 7 R 5 [E(N t Bu) 2 CPh] (E = Si, Ge, Sn). In the case of the silylene derivative, the solid-state structure was determined by single crystal X-ray diffraction.

While smaller polyhedral oligomeric silsesquioxanes T n R n (POSS) are readily accessible or even commercially available, unambiguously authenticated larger systems (n>12) have barely been reported. Synthesis and isolation procedures are lengthy, and yields are often very low. Herein, we present the surprisingly straightforward and high-yielding access to the phenyl-substituted derivative of a so far only postulated second D 3h -symmetric T 14 isomer and with that the largest crystallographically characterized POSS cage with organic substituents. Treatment of the commercially available incompletely condensed T 7 Ph 7 (OH) 3 silsesquioxane with catalytic amounts of trifluoromethanesulfonic acid results in high yields of the T 14 Ph 14 framework, which is isolated in crystalline form by a simple work-up. D 3h -T 14 Ph 14 was analyzed by single crystal X-ray diffraction, multinuclear NMR spectroscopy and thermal analysis. The relative energies of all four theoretically possible T 14 Ph 14 isomers were determined by optimization of the corresponding structure using DFT methods., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Diboriranides are the smallest conceivable monoanionic aromatic cycles, yet only limited examples have been reported and their reactivity and complexation behavior remain completely unexplored. We report a straightforward synthesis of the first peraryl diboriranide c-(DurB) 2 CPh - as its lithium salt in three steps via the corresponding non-classical diborirane from a readily available 1,2-dichlorodiborane(4) (Dur=2,3,5,6-tetramethylphenyl). With the preparation and complete characterization of representative complexes with tin, copper, gold and zinc, we demonstrate the strong preference of the diboriranide for σ-type coordination modes towards main group and transition metal centers under unperturbed retention of the three-membered B 2 C-ring's 2e - π-system., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Heavier tetrylenes attract attention for their potential in synthesis, catalysis and small molecule activation. The coordination by N-heterocyclic carbenes (NHCs) and cyclic (alkyl)(amino)carbenes (CAACs) results in substantial structural and electronic differences although typically only one of these yields stable derivatives for one and the same tetrylene. We now report both NHC- and CAAC-coordination to a bridged bis(germylene) motif. The NHC-coordinated bis(germylene) exhibits pyramidal germanium centers with lone pairs of electrons, while with CAAC an unprecedented stable bis(germene) with two Ge=C bonds is isolated. Spectroscopic and crystallographic evidence as well as DFT calculations confirm the effects of σ,π-conjugation between the two germanium centers in both cases. The coordination of NHC is reversible as the reaction with BPh 3 liberates the transient bis(germylene) and thus provides an alternative low-temperature route towards polymers with Ge=Ge bonds., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Starting from tetrakis(trimethylsilyl)cyclobutadiene and an amidinate-supported silylene of the Roesky-type, a sequence of addition and reduction cleanly gives the elusive silapyramidane via an isolable cyclobutene intermediate with an exocyclic Si═C bond. The silapyramidane features an unusually shielded 29 Si NMR resonance at -448.3 ppm for the apex silicon atom. Treatment with Fe 2 (CO) 9 results in the formation of the corresponding silapyramidane-iron complex. Silapyramidane also reacts with the cyclobutadiene starting material to cleanly afford a fluorescent spirobis(silole).

Schnöckel's [(AlCp*) 4 ] and Jutzi's [SiCp*][B(C 6 F 5 ) 4 ] (Cp*=C 5 Me 5 ) are landmarks in modern main-group chemistry with diverse applications in synthesis and catalysis. Despite the isoelectronic relationship between the AlCp* and the [SiCp*] + fragments, their mutual reactivity is hitherto unknown. Here, we report on their reaction giving the complex salts [Cp*Si(AlCp*) 3 ][WCA] ([WCA] - =[Al(OR F ) 4 ] - and [F{Al(OR F ) 3 } 2 ] - ; R F =C(CF 3 ) 3 ). The tetrahedral [SiAl 3 ] + core not only represents a rare example of a low-valent silicon-doped aluminium-cluster, but also-due to its facile accessibility and high stability-provides a convenient preparative entry towards low-valent Si-Al clusters in general. For example, an elusive binuclear [Si 2 (AlCp*) 5 ] 2+ with extremely short Al-Si bonds and a high negative partial charge at the Si atoms was structurally characterised and its bonding situation analysed by DFT. Crystals of the isostructural [Ge 2 (AlCp*) 5 ] 2+ dication were also obtained and represent the first mixed Al-Ge cluster., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

The growth of (semi-)metal clusters is pivotal for nucleation processes in gaseous and condensed phases. We now report the isolation of intermediates during the expansion of a stable unsaturated silicon cluster (siliconoid) by a single germanium atom through a sequence of substitution, rearrangement and reduction. The reaction of ligato-lithiated hexasilabenzpolarene LiSi 6 Tip 5 (1Li⋅(thf) 2 , Tip=2,4,6-triisopropylphenyl) with GeCl 2 ⋅NHC (NHC=1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) initially yields the product with exohedral germanium(II) functionality, which then inserts into an Si-Si bond of the Si 6 scaffold. The concomitant transfer of the chloro functionality from germanium to an adjacent silicon preserves the electron-precise nature of the formed endohedral germylene. Full incorporation of the germanium heteroatom to the Si 6 Ge cluster core is finally achieved either by reduction under loss of the coordinating NHC or directly by reaction of 1Li⋅(thf) 2 with GeCl 2 ⋅1,4-dioxane., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Transition metal π-allyl complexes are key reagents/intermediates of various catalytic and stoichiometric allylation reactions. We now report the first transition metal complex of a heavier allylic π-system. The η 3 -Si 2 Ge allyl nickel complex is formally obtained by the oxidative addition of the Si-Cl bond of the heavier vinylidene [R 2 (Cl)Si-(R)Si═(NHC)Ge:] to [Ni(COD) 2 ] (R = 2,4,6-triisopropylphenyl; NHC = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene; COD = 1,5-cyclooctadiene). Due to geometric constraints, the coordination to the Ni(II) center occurs through the formal Si═Ge double bond instead of the residual lone pair of electrons at germanium. In contrast, the Si-N bond of the analogous vinylidene [R 2 (Me 2 N)Si-(R)Si═(NHC)Ge:] (obtained by nucleophilic substitution of Cl by NMe 2 ) does not oxidatively add to Ni(0), and a hydridosilagermene-η 2 -nickel complex is obtained instead. The formation of this complex necessarily implies the isomerization of the heavier vinylidene to the corresponding heteroalkyne with the Si≡Ge triple bond in the coordination sphere of nickel followed by the activation of a C-H bond of one of the isopropyl groups of an N-heterocyclic carbene (NHC) ligand.

The continuously decreasing size of device features in microelectronics draws growing attention to the structuring of silicon at the molecular level with powerful tools provided by synthetic chemistry. Silicon clusters are of particular importance in this regard not only as potential precursors for silicon deposition but also as well-defined model systems for bulk and surfaces of silicon at the nanoscale as well as possible starting points for future construction of molecularly precise device structures. This review aims to give a comprehensive overview about the state of the art in the synthesis of molecular silicon clusters, which are grouped into (1) electron-precise saturated clusters, (2) soluble polyhedral Zintl anions, and (3) unsaturated silicon clusters, the so-called siliconoids. Particular attention is paid to functionalization as it is generally considered a necessary prerequisite for the design and construction of more extended systems. The interrelations between the three different classes of molecular silicon clusters, e.g., arising from the introduction of negatively charged functional groups, are highlighted on grounds of NMR properties and computed electronic structures.

Transition-metal complexes of cyclopropenes occur as fleeting intermediates of numerous metal-catalyzed organic transformations. A heavier analogue has now been obtained from the reaction of an NHC-stabilized silagermenylidene, bis(1,5-cyclooctadiene)nickel(0), and 1 equiv of N-heterocyclic carbene (NHC). The residual chloro functionality at the germanium end of the coordinated Ge═Si moiety of the thus formed 1 H -disilagermirene is easily exchanged by treatment with anionic nucleophiles, which provides access to a series of differently substituted Si 2 Ge-cyclopropenes as nickel complexes in excellent yields. NMR spectroscopic data, X-ray crystallographic analysis, and DFT calculations indicate a coordination mode different from the metallacyclopropane and π-complex extremes of the Dewar-Chatt-Duncanson model: the σ-component of the Ge═Si double bond acts as donor and acceptor, leaving behind a nearly unsupported Si-Ge π-bond.

The metathesis of carbon-carbon double bonds-the 'reshuffling' of their constituting carbene fragments-is a tremendously important preparative tool in industry and academia. Metathesis of heavier alkene homologues is restricted to occasional unproductive examples in phosphorus chemistry and cross-metathesis to mixed heavier alkynes. We now report the thermally induced, transition-metal-free metathesis of purpose-built unsymmetrically substituted digermenes. The A 2 Ge=GeAB starting materials are thus converted to symmetrically substituted derivatives of the A 2 Ge=GeA 2 and ABGe=GeAB types. The use of tethered auxiliary donors (dimethylaniline groups) in substituents B ensures intramolecular donor-acceptor stabilization of the transient germylene fragments, the intermediacy of which is proven by trapping experiments. Density functional theory calculations shed light on the thermodynamic driving force of the metathesis and validate the crucial role of the tethered donor. With an analogously equipped bridged tetragermadiene precursor (A 2 Ge=GeB-X-BGe=GeA 2 ), heavier acyclic diene metathesis polymerization occurs, in analogy to the widespread acyclic diene metathesis (ADMET) polymerization in the carbon case, yielding a polydigermene.

We report the reactivity of isolable Au(i)-hydride stabilized by an NHC-coordinated diphosphene towards substrates containing C-C and N-N multiple bonds (NHC = N-heterocyclcic carbene). Reactions with dimethyl acetylenedicarboxylate and azobenzene lead to a trans-addition of the Au(i)-H across the C-C triple bond and the N-N double bond, respectively. In contrast, the reaction with ethyl diazoacetate affords a gold(i)-hydrazonide as the 1,1-addition product to the terminal nitrogen atom. With phenyl acetylene, the corresponding Au(i)-alkynyl complex is obtained under the elimination of dihydrogen. Strikingly, diphosphene-containing Au(i)-hydride is more reactive - affording different products in some cases - than a related NHC-stabilized Au(i)-hydride without the mediating diphosphene moiety.

The versatile reactivities of disilenides and digermenide, heavier analogues of vinyl anions, have significantly expanded the pool of silicon and germanium compounds with various unexpected structural motifs in the past two decades. We now report the synthesis and isolation of a cyclic heteronuclear vinyl anion analogue with a Si=Ge bond, potassium silagermenide as stable thf-solvate and 18-c-6 solvate by the KC 8 reduction of germylene or digermene precursors. Its suitability as synthon for the synthesis of functional silagermenes is proven by the reactions with chlorosilane and chlorophospane to yield the corresponding silyl- and phosphanyl-silagermenes. X-ray crystallographic analysis, UV/Vis spectroscopy and DFT calculations revealed a significant degree of π-conjugation between N=C and Si=Ge double bonds in the title compound., (© 2020 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Reactions of silylenes with heavier chalcogens (E) typically result in Si=E double bonds or their π-addition products. In contrast, the oxidation of a silylene-functionalized unsaturated silicon cluster (siliconoid) with Group 16 elements selectively yields cluster expanded siliconoids Si 7 E (E=S, Se, Te) fully preserving the unsaturated nature of the cluster scaffold as evident from the NMR signatures of the products. Mechanistic considerations by DFT calculations suggest the intermediacy of a Si 6 siliconoid with exohedral Si=E functionality. The reaction thus may serve as model system for the oxidation of surface-bonded silylenes at Si(100) by chalcogens and their diffusion into the silicon bulk., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

Recent studies of low-valent main group species underscore their resemblance to transition metal complexes with regards to the ability to activate small molecules. Here, we report synthesis and full characterisation of the persistent (hypersilyl)(pentamethylcyclopentadienyl)silylene Cp*[(Me3Si)3Si]Si: as well as its unique reactivity. Silylene Cp*[(Me3Si)3Si]Si: activates dihydrogen to give the corresponding dihydrosilane Cp*[(Me3Si)3Si]SiH2 at particularly mild conditions as well as ethylene to afford the three-membered cyclic silirane c-Cp*[(Me3Si)3Si]Si(H2CCH2). The addition of N-heterocyclic carbene NHC (NHC = 1,3,4,5-tetramethyl-imidazol-2-ylidene) to dihydrosilane Cp*[(Me3Si)3Si]SiH2 induces the reductive elimination of Cp*H, which according to DFT calculations is thermodynamically preferred over H2 elimination. With NHC, Cp*[(Me3Si)3Si]Si: forms a typical donor-acceptor complex with concomitant change in hapticity of the Cp* ligand from η2 to η1 (σ). In contrast, the reaction with the N-heterocyclic silylene c-[(CH[double bond, length as m-dash]CH(tBuN)2]Si: leads to an unusual "masked" disilene with the former Cp* ligand bridging the two silicon centres. The heterodimer is stable in the solid state, but dissociates reversibly to the constituting silylene fragments in solution.

Reaction of a silylene-functionalized Si6 siliconoid with CO in the presence of catalytic quantities of a nickel(0) complex results in the complete cleavage of the CO triple bond, but preserves the Si6 scaffold with an exohedrally incorporated Si[double bond, length as m-dash]C enol ether bridge. The uncompromised cluster core emphasizes the role of the so-called benzpolarene motif as the energetic silicon pendants of benzene in carbon chemistry.

Understanding the characteristics of radicals formed from silicon-containing heavy analogues of alkenes is of great importance for their application in radical polymerization. Steric and electronic substituent effects in compounds such as phosphasilenes not only stabilize the Si=P double bond, but also influence the structure and species of the formed radicals. Herein we report our first investigations of radicals derived from phosphasilenes with Mes, Tip, Dur, and NMe 2 substituents on the P atom, using muon spin spectroscopy and DFT calculations. Adding muonium (a light isotope of hydrogen) to phosphasilenes reveals that: a) the electron-donor NMe 2 and the bulkiest Tip-substituted phosphasilenes form several muoniated radicals with different rotamer conformations; b) bulky Dur-substituted phosphasilene forms two radicals (Si- and P-centred); and c) Mes-substituted phosphasilene mainly forms one species of radical, at the P centre. These significant differences result from intramolecular substituent effects., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Main group analogues of cyclobutane-1,3-diyls are fascinating due to their unique reactivity and electronic properties. So far only heteronuclear examples have been isolated. Here we report the isolation and characterization of all-silicon 1,3-cyclobutanediyls as stable closed-shell singlet species from the reversible reactions of cyclotrisilene c-Si 3 Tip 4 (Tip=2,4,6-triisopropylphenyl) with the N-heterocyclic silylenes c-[(CR 2 CH 2 )(NtBu) 2 ]Si: (R=H or methyl) with saturated backbones. At elevated temperatures, tetrasilacyclobutenes are obtained from these equilibrium mixtures. The corresponding reaction with the unsaturated N-heterocyclic silylene c-(CH) 2 (NtBu) 2 Si: proceeds directly to the corresponding tetrasilacyclobutene without detection of the assumed 1,3-cyclobutanediyl intermediate., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Taking advantage of pendant tetrylene side-arms, stable unsaturated Si 6 silicon clusters (siliconoids) with the benzpolarene motif (the energetic counterpart of benzene in silicon chemistry) are successfully employed as ligands towards Group 9 metals. The pronounced σ-donating properties of the tetrylene moieties allow for sequential oxidative addition and reductive elimination events without complete dissociation of the ligand at any stage. In this manner, either covalently linked or core-expanded metallasiliconoids are obtained. [Rh(CO) 2 Cl] 2 inserts into an endohedral Si-Si bond of the silylene-functionalized hexasilabenzpolarene leading to an unprecedented coordination sphere of the Rh centre with five silicon atoms in the initial product, which is subsequentially converted to a simpler derivative under reconstruction of the Si 6 benzpolarene motif. In the case of [Ir(cod)Cl] 2 (cod = 1,5-cyclooctadiene) a similar Si-Si insertion leads to the contraction of the Si 6 cluster core with concomitant transfer of a chlorine atom to a silicon vertex generating an exohedral chlorosilyl group. Metallasiliconoids are employed in the isomerization of terminal alkenes to 2-alkenes as a catalytic benchmark reaction, which proceeds with competitive selectivities and reaction rates in the case of iridium complexes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Unsaturated charge-neutral silicon clusters (siliconoids) are important as gas-phase intermediates between molecules and the elemental bulk. With stable zirconocene- and hafnocene-substituted derivatives, we here report the first examples containing directly bonded transition-metal fragments that are readily accessible from the ligato-lithiated Si 6 siliconoid (1Li) and Cp 2 MCl 2 (M=Zr, Hf). Charge-neutral siliconoid ligands with pending tetrylene functionality were prepared by the reaction of amidinato chloro tetrylenes [PhC(NtBu) 2 ]ECl (E=Si, Ge, Sn) with 1Li, thus confirming the principal compatibility of such low-valent functionalities with the unsaturated Si 6 cluster scaffold. The pronounced donor properties of the tetrylene/siliconoid hybrids allow for their coordination to the Fe(CO) 4 fragment., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

We report the influence of N-heterocyclic carbenes (NHCs) on the hydrolysis of a diphosphene TerP[double bond, length as m-dash]PTer (1; Ter = 2,6-Mes 2 C 6 H 3 ; Mes = 2,4,6-Me 3 C 6 H 2 ), a phosphorus-analogue of an alkene. The diphosphene 1 itself is completely inert towards water. However, NHCs have been found to activate 1 towards ready hydrolysis. While sterically less-encumbered NHCs react with 1 affording NHC-adducts which are in equilibrium with 1 in solution, sterically encumbered NHCs do not bind to 1 at all. Interestingly, in both of these situations hydrolysis of the P[double bond, length as m-dash]P motif proceeds efficiently. At low temperatures, sterically less-encumbered NHCs are catalytic while the sterically encumbered NHCs play a catalytic role at room temperature. To gain insight on this striking influence of NHCs on the hydrolysis of diphosphene detailed low-temperature 31 P-NMR studies along with theoretical calculations have been carried out. In addition, systematic hydrolysis studies of all the NHCs used in this study have also been performed.

Unsaturated silicon clusters (siliconoids) are short-lived intermediates during the transition from molecules to the elemental bulk; stable representatives reiterate surface features of silicon materials. The incorporation of suitable heteroatoms into the cluster scaffold of stable siliconoids extends this analogy to the technological process of silicon doping. Here, we report boron- and phosphorus-containing heterosiliconoids with BSi 5 and PSi 5 core based on the global minimum Si 6 R 6 platform (dubbed benzpolarene for its relationship to benzene). The reductive cleavage of an SiR 2 moiety (R = 2,4,6-iPr 3 C 6 H 2 ) from Si 6 R 6 selectively yields a dianionic Si 5 R 4 2- cluster as its lithium salt. Treatment with Me 3 SiCl affords the corresponding trimethylsilyl-substituted (Me 3 Si) 2 Si 5 R 4 . Reaction of Si 5 R 4 2- with iPr 2 NECl 2 (E = B, P) yields the unprecedented p- and n-doped heterosiliconoids iPr 2 NESi 5 R 4 . Their peculiar electronic features are compared to those of the hexasilabenzpolarene starting material on grounds of NMR spectroscopy, X-ray diffraction, and DFT calculations.

An NHC-coordinated diphosphene is employed as ligand for the synthesis of a hydrocarbon-soluble monomeric Au I hydride, which readily adds CO 2 at room temperature yielding the corresponding Au I formate. The reversible reaction can be expedited by the addition of NHC, which induces β-hydride shift and the removal of CO 2 from equilibrium through the formation of an NHC-CO 2 adduct. The Au I formate is alternatively formed by dehydrogenative coupling of the Au I hydride with formic acid (HCO 2 H), thus in total establishing a reaction sequence for the Au I hydride mediated dehydrogenation of HCO 2 H as chemical hydrogen storage material., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We report the preparation of α-chlorosilyl- and acyl-substituted digermenes. Unlike the corresponding transient disilenes, these species with a Ge=Ge double bond show an unexpectedly low tendency for cyclization, but in turn are prone to thermal Ge=Ge bond cleavage. Triphenylsilyldigermene has been isolated as a crystalline model compound, and is the first fully characterized example of a neutral digermene with an A 2 GeGeAB substitution pattern. Spectroscopic and computational evidence prove the constitution of 1-adamantoyldigermene as a first persistent species with a heavy double bond conjugated with a carbonyl moiety., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The two-electron reduction of the dismutational isomer of a 1,4-digermatetrasilabenzene cleaves one of the aryl groups in ligato-position and thus yields an unsaturated anionic Ge2Si4 cluster (digermatetrasila-benzpolarenide) with the negative charge at a Ge center. The regioselective positioning of the germanium centers in one nudo- and one ligato-position provides insight into the rearrangement of the Si4E2-scaffold of the dismutational isomers of hexatetrelbenzenes under reductive conditions with concomitant aryl group cleavage (E = Si and Ge).

Herein, we report the synthesis and molecular structures of various magnesium(ii)-phosphate monoesters. By using a bulky aryl substituted phosphate monoester, ArOPO 3 H 2 (Ar = 2,6-(CHPh 2 ) 2 -4-tBu-C 6 H 2 ), we have reproducibly assembled mono-, di-, tetra- (cage and ring), hexa-, and polynuclear magnesium(ii)-phosphate monoesters. Interestingly, the hexanuclear magnesium(ii)-phosphate monoester encapsulates an open-cage dodecanuclear water cluster.

We report the reversible coordination of the N-heterocyclic carbene (NHC), NHC iPr 2 Me 2 (NHC iPr 2 Me 2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene), to silicon(IV)-halides, SiCl 4 , MeSiCl 3 , Me 2 SiCl 2 , and Me 3 SiCl. Predicted as well as experimentally determined thermodynamic parameters of these equilibria confirm that the complexation constant increases with the Lewis acidity of the silicon halides. In contrast, the more σ-donating N-heterocyclic carbene, NHC Me 4 (NHC Me 4 = 1,3,4,5-tetramethylimidazol-2-ylidene), does not show any signs of dissociation from the corresponding SiCl 4 and Me 2 SiCl 2 adducts even at higher temperatures. As a consequence, NHC iPr 2 Me 2 in donor-acceptor stabilized Si(II)- and Ge(II)-dimethyl complexes, NHC iPr 2 Me 2 ·GeMe 2 ·Fe(CO) 4 and NHC iPr 2 Me 2 ·SiMe 2 ·Fe(CO) 4 , is readily replaced by NHC Me 4 .

Small- to medium-sized clusters occur in various areas of chemistry, for example, as active species of heterogeneous catalysis or as transient intermediates during chemical vapor deposition. The manipulation of stable representatives is mostly limited to the stabilizing ligand periphery, virtually excluding the systematic variation of the property-determining cluster scaffold. We now report the deliberate expansion of a stable unsaturated silicon cluster from six to seven and finally eight vertices. The consecutive application of lithium/naphthalene as the reducing agent and decamethylsilicocene as the electrophilic source of silicon results in the expansion of the core by precisely one atom with the potential of infinite repetition., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The recent progress in the synthesis of partially substituted neutral silicon clusters (siliconoids) revealed unique structures and electronic anisotropies that are reminiscent of bulk and nano surfaces of silicon. Here, we report the selective 2-lithiation of the global minimum Si 6 R 6 siliconoid at a different vertex than in the previously reported isomeric 4-lithiated derivative (R = 2,4,6- i Pr 3 C 6 H 2 ). In order to enable an intuitive distinction of the vertices of the global minimum Si 6 R 6 scaffold (which can be considered the silicon analogue of benzene in terms of thermodynamic stability), we introduce a novel nomenclature in analogy to the ortho - meta - para nomenclature of disubstituted benzenes. By treatment of the 2-lithiated Si 6 cluster with Me 3 SiCl, SiCl 4 H 3 B·SMe 2 , (Me 2 N) 2 PCl as well as with carboxylic acid chlorides RCOCl (R = t Bu, Ph) various 2-functionalized Si 6 clusters were obtained and characterized in solution and - in most cases - the solid state. The structural and spectroscopic effect of the position of the newly introduced functional group is discussed by comparison to the corresponding 4-functionalized derivatives.

Small unsaturated phosphacycles are versatile reagents owing to their strain and the added functionality of the double bond and the phosphorus lone pair. Herein we report the synthesis and isolation of the smallest possible cyclic phosphasilene as a stable adduct with an N-heterocyclic carbene (NHC). First reactivity studies show a) that the PSi 2 ring is a competent ligand to the Fe(CO) 4 fragment via the phosphorus lone pair and b) that the abstraction of the NHC by BPh 3 results in the rapid head-to-head or head-to-tail dimerization of the PSi 2 unit. The relatively facile NHC cleavage indicates that the P=Si double bond is available for further manipulation., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Ionic liquids (ILs) are promising electrolytes, although their often high viscosity remains a serious drawback. The latter can be addressed by the introduction of multiple ether functionalization. Based on the highly atom efficient synthesis of tris(2-ethoxyethyl) phosphine, several new phosphonium ionic liquids were prepared, which allows studying the influence of the ether side chains. Their most important physicochemical properties have been determined and will be interpreted using established approaches like ionicity, hole theory, and the Walden plot. There is striking evidence that the properties of phosphonium ionic liquids with the methanesulfonate anion are dominated by aggregation, whereas the two triple ether functionalized ILs with the highest fluidity show almost ideal behavior with other factors being dominant. It is furthermore found that the deviation from ideality is not significantly changed upon introduction of the ether side chains, although a very beneficial impact on the fluidity of ILs is observed. Multiple ether functionalization therefore proves as a powerful tool to overcome the disadvantages of phosphonium ionic liquids with large cations., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Syntheses and structures of anionic arylphosphate monoesters [ArOP(O) 2 (OH)] - (Ar = 2,6-CHPh 2 -4-R-C 6 H 2 ; R = Me/Et/ i Pr/ t Bu) with different counter cations are reported. The counter cations were varied systematically: imidazolium cation, 2-methyl imidazolium cation, N -methyl imidazolium cation, N , N '-alkyl substituted imidazolium cation, 1,4-diazabicyclo[2.2.2]octan-1-ium cation, 4,4'-bipyridinium dication, and magnesium(II) dication. The objective was to examine if the supramolecular structure of anionic arylphosphate monoesters could be modulated by varying the cation. It was found that an eight-membered P 2 O 4 H 2 -hydrogen-bonded dimeric motif involving intermolecular H-bonding between the [P(O)(OH)] unit of the anionic phosphate monoester along with the counter cation is formed with 2-methyl imidazolium cation, N -methyl imidazolium cation, N , N '-alkyl substituted imidazolium cation, 1,4-diazabicyclo[2.2.2]octan-1-ium cation, and magnesium(II) dication; both discrete and polymeric H-bonded structures are observed. In the case of imidazolium cations and 1,4-diazabicyclo[2.2.2]octan-1-ium cation, the formation of one-dimensional polymers (single lane/double lane) was observed. On the other hand, two types of phosphate motifs, intermolecular H-bonded dimer and an open-form, were observed in the case of 4,4'-bipyridinium dication., Competing Interests: The authors declare no competing financial interest.

Permethylated disila[2]metallocenophanes of silicon, germanium, tin, lead, 2 a-d, (tetrelocenophanes) and antimony, 3 a,b, (pnictogenocenophanes) are described. In the case of antimony, a chloro-substituted stibonocenophane, 3 a, as well as cationic stibonocenophanium tetrachloroaluminate and tetraphenylborate salts, 3 b[X] (X=[AlCl 4 ], [BPh 4 ]), were synthesized. These represent the first examples of metallocenophanes of any Group 15 element. All compounds were studied in solution and in the solid state. Without exception the ansa-bridge exerts a strong influence on the bending angle of the two Cp-ligands. For disila[2]plumbocenophane, 2 d, its reactivity towards Group 15 halides was probed. Treatment of disila[2]plumbocenophane, 2 d, with two equivalents of phosphorus(III) chloride or arsenic(III) chloride, results in a ring-opening reaction and gives the bis(dihalopnictogenyl)-substituted products, 4 a,b., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)