Synthesis and Investigation of a Soluble Distannene with no Trans-Bent Angle or Twisting in the Solid-State.

By treating KSiiPr3 with Sn[N(SiMe3)2]2 the distannene Sn2(TIPS)4 (TIPS=SiiPr3) is formed in a metathesis reaction. The crystal structure analysis of Sn2(TIPS)4 reveals a planar arrangement of the substituents in the solid-state and hence the second planar alkene like distannene of its kind. Due to the TIPS substituents, Sn2(TIPS)4 is well soluble in all commonly used organic solvents, opening the door for various analytics and reactivity studies. Due to its stability in solution, various reactions can be performed such as cycloaddition reactions with 2,3-dimethyl-1,3-butadiene (DMBD) and TMS-azide.

Synthesis and Reactivity of Fluorenyl-Based Germanium(II) Compounds.

We present the synthesis of alkyl-substituted germylenes GeFlu2, Ge(FluTMS)2, and FluTMSGeCl (Flu = 9H-fluorenyl, FluTMS = 9-trimethylsilyl-9H-fluorenyl) using bulky fluorenyl ring systems and modifications of that. GeFlu2 can only be crystallized as its three-membered ring trimer, whereby the reaction is accompanied by the formation of several byproducts, such as [Li(THF)4][Ge(Ge3Flu7H)]. These results led to the modification of the fluorenyl framework by substitution the one H atom in the 9-position by a TMS group. With the synthesis of the corresponding Li salt LiFluTMS, Ge(FluTMS)2 could be isolated in good yields in a further reaction. The homoleptic Ge(FluTMS)2 is found in its crystalline form as a monomer and thus belongs to the series of monomeric alkyl-substituted germylenes. Also, the corresponding monoalkyl-substituted halogenido germylene was isolated as a four-membered ring tetramer [FluTMSGeCl]4 during an unselective reaction. However, FluTMSGeCl undergoes significant stabilization through the formation of the monomeric phosphane adduct FluTMSGeCl·PEt3, which greatly increases the selectivity of the reaction. During further reactions of Ge(FluTMS)2 with a GeBr solution (toluol/nPr3P), more impressions of the reactivity of Ge(I)X solutions with germylenes were achieved, showing that those germylenes take part in the disproportionation reaction of metastable Ge(I) solutions to give oxidized Ge(IV) compounds like (FluTMS)2GeBr2.

Tuning the electronic structure of gold cluster-assembled materials by altering organophosphine ligands.

Superatomic clusters can be assembled to build bulk matter, where the individual characteristics are preserved. The main benefit of these materials over conventional bulk species is the capability to tailor their features by altering the physicochemical identities of individual clusters. Electronic properties of metal clusters can be modified by a protective shell of ligands that attach to the surface and make the whole nanoparticle soluble in organic or aqueous solvents. In the present work, we demonstrate that properly chosen ligands provide not only steric protection from aggregation but also tune the redox activity of metal clusters. We investigate the role of the ligands in electronic structure tunability and ligand-field splitting. Our first-principles calculations agree with the experiments, showing that phosphine-protected gold materials are small gap semiconductors. The obtained bandgaps strongly depend on the ligand used. Hence, using phosphine and organophosphine ligands should be feasible and promising while designing the novel superatom-based materials since the desired range of the bandgap might be achieved (by the proper choice of the ligand).

Wearing face masks as a potential source for inhalation and oral uptake of inanimate toxins - A scoping review.

BACKGROUND: From 2020 to 2023 many people around the world were forced to wear masks for large proportions of the day based on mandates and laws. We aimed to study the potential of face masks for the content and release of inanimate toxins. METHODS: A scoping review of 1003 studies was performed (database search in PubMed/MEDLINE, qualitative and quantitative evaluation). RESULTS: 24 studies were included (experimental time 17 min to 15 days) evaluating content and/or release in 631 masks (273 surgical, 228 textile and 130 N95 masks). Most studies (63%) showed alarming results with high micro- and nanoplastics (MPs and NPs) release and exceedances could also be evidenced for volatile organic compounds (VOCs), xylene, acrolein, per-/polyfluoroalkyl substances (PFAS), phthalates (including di(2-ethylhexyl)-phthalate, DEHP) and for Pb, Cd, Co, Cu, Sb and TiO2. DISCUSSION: Of course, masks filter larger dirt and plastic particles and fibers from the air we breathe and have specific indications, but according to our data they also carry risks. Depending on the application, a risk-benefit analysis is necessary. CONCLUSION: Undoubtedly, mask mandates during the SARS-CoV-2 pandemic have been generating an additional source of potentially harmful exposition to toxins with health threatening and carcinogenic properties at population level with almost zero distance to the airways.

Au30(PiPr2nBu)12Cl6-An Open Cluster Provides Insight into the Influence of the Sterical Demand of the Phosphine Ligand in the Formation of Metalloid Gold Clusters.

Phosphine-stabilized gold clusters are an important subgroup of metalloid gold cluster compounds and are important model compounds for nanoparticles. Although there are numerous gold clusters with different phosphine ligands, the effect of phosphine on cluster formation and structure remains unclear. While the linear alkyl-substituted phosphine gold chlorides result in a Au32 cluster, the bulky tBu3P leads to a Au20 cluster. The reduction of (iPr2nBuP)AuCl, with the steric demand of the phosphine ligand between the mentioned phosphines, results in the successful synthesis and crystallization of a new metalloid gold cluster, Au30(PiPr2nBu)12Cl6. Its structure is similar to the Au32 cluster but with two missing AuCl units. The UV/Vis studies and quantum chemical calculations show the similarities between the two clusters and the influence of the phosphine ligand in the synthesis of metalloid gold clusters.

[(thf)5Ln(Ge9{Si(SiMe3)3}2)] (Ln = Eu, Sm, Yb): Capping Metalloid Germanium Cluster with Lanthanides.

We report the synthesis of three neutral complexes with different coordination modes of a di-silylated metalloid germanium cluster to divalent lanthanides [(thf)5Ln(ηn-Ge9(Hyp)2)] (Ln = Yb (1, n = 1); Eu (2, n = 2, 3), Sm (3, n = 2, 3); Hyp = Si(SiMe3)3) by the salt metathesis of LnI2 with K2[Ge9(Hyp)2] in THF. The complexes were characterized by elemental analysis, nuclear magnetic resonance and UV-vis-NIR spectroscopy, and single-crystal X-ray diffraction. In thf solution, the formation of contact or solvate-separated ion pairs depending on the concentration is assumed. Compound 2 exhibits a blue luminescence typical for Eu2+. The solid-state magnetic measurements of compounds 2 and 3 confirm the presence of divalent europium and samarium, respectively.

Stabilization of Colloidal Germanium Nanoparticles: From the Study to the Prospects of the Application in Thin-Film Technology.

We present the stabilization of halide-terminated Ge nanoparticles prepared via a disproportionation reaction of metastable Ge(I)X solutions with well-defined size distribution. Further tailoring of the stability of the Ge nanoparticles was achieved using variations in the substituent. Ge nanoparticles obtained in this way are readily dispersed in organic solvents, long-term colloidally stable, and are perfect prerequisites for thin-film preparation. This gives these nanomaterials a future in surface-dependent optical applications, as shown for the halide-terminated nanoparticles.

Multilayer Langmuir Film of Monodisperse Au Nanoclusters: Unusual Growth via Bilayers.

The assembly of nanomaterials into thin films is an important area in the nanofabrication of novel devices. The monodispersity of nanoparticles plays an essential role in the resulting quality of the assembled mono- and multilayers. Larger polydispersity leads to smaller lateral correlation lengths and smaller domains of aligned nanoparticles, thus resulting in more point and line defects. Perfectly monodisperse nanoparticles should therefore minimize the number of defects in the assembled films. Despite tremendous progress in reducing the polydispersity of nanoparticles, there has been limited research on the assembly of thin films out of perfectly monodisperse nanoclusters. Here, we show a formation of Langmuir films using perfectly monodisperse gold nanoclusters with composition Au32(nBu3P)12Cl8 exhibiting a diameter of 1.8 nm. Using both in situ and ex situ small-angle X-ray scattering, we show that the monolayer formed on a Langmuir-Blodgett trough exhibits long-range order. Moreover, after compressing the monolayer, we found that the stress accumulated prior to the monolayer collapse triggers a transition to a short-range order not previously reported. If such monolayer is compressed further, the second layer is not formed as in the case of standard nanoparticles. Instead, a growth of islands by an odd number of layers is observed, leading to a thin film with a structure consisting of two different orientations of the hexagonal lattice. Such anomalous behavior may have implications for the possibilities of thin-film formation.

Oxidation of [Ge9{Si(SiMe3)3}3]- with LnI3 (Ln = Eu, Sm, Yb): Isomerism of Metalloid Germanium Clusters.

The oxidation of K[Ge9(Hyp)3] (Hyp = Si(SiMe3)3) with lanthanide triiodides LnI3 (Ln = Eu, Sm, Yb) leads to the formation of novel clusters with a Ge18-core isolated as a co-crystallizate of Ge*18(Hyp)6 (1a) and Ge18(Hyp)5(Si(SiMe3)2)(SiMe3) (1b). Clusters 1a and 1b differ distinctly from the known cluster Ge18(Hyp)6 (A), which has been found earlier in the reaction of K[Ge9(Hyp)3] with FeCl2 and now identified as an intermediate product in the production of compounds 1a and 1b. These three compounds A, 1a, and 1b are thus structural isomers being the first example of genuine isomerism in metalloid main-group cluster compounds.

Oxidative Coupling of [Ge9(Si(SiMe3)3)2]2- with f Elements.

We report the reactions of K2[Ge9(Hyp)2] (Hyp = Si(SiMe3)3) with (thf)3YbI3, ThI4, and UCl4, leading to the oxidative coupling of the metalloid germanium cluster to form the dimeric dianion [Ge18(Hyp)4]2-. The novel dimerized Ge18-cluster was isolated and characterized by single-crystal X-ray diffraction analysis as a component of ionic compounds [Yb(thf)6][Ge18(Hyp)4] (1) and [K(2.2.2-crypt)]2[Ge18(Hyp)4] (2) with two different counterions. The dihedral angle between two intact Ge9 cages depends on the counterions, which was also studied by quantum-chemical calculations.

Au20 (t Bu3 P)8 : A Highly Symmetric Metalloid Gold Cluster in Oxidation State 0.

Metalloid gold clusters have unique properties with respect to size and structure and are key intermediates in studying transitions between molecular compounds and the bulk phase of the respective metal. In the following, the synthesis of the all-phosphine protected metalloid cluster Au20 (t Bu3 P)8 , solely built from gold atoms in the oxidation state of 0 is reported. Single-crystal X-ray analysis revealed a highly symmetric hollow cube-octahedral arrangement of the gold atoms, resembling gold bulk structure. Quantum-chemical calculations illustrated the cluster can be described as a 20-electron superatom. Optical properties of the compound have shown molecular-like behavior.

Ge14Br8-xClx(PEt3)4: Insight into the Reaction Route to Metalloid Clusters of Germanium.

The isolation of the germanium mixed halide cluster Ge14Br8-xClx(PEt3)4 (2) by the reaction of a metastable GeIBr solution (toluene/PEt3) with GeCl2·dioxane provides new insights into the complex formation mechanism of metalloid germanium clusters through the disproportionation reaction of GeIX (X = Cl and Br). It is shown that the GeII halide is involved in at least two steps in the build-up reaction of 2. The molecular structure of 2 is presented together with a plausible reaction mechanism leading to the binary cluster Ge14Br8(PEt3)4 and future aspects of these findings.

Cascade-Reaction Leading to an Intramolecular [2 + 4] Cycloaddition of a Phenyl Group by a Reactive Ge═Si Double Bond.

The reaction of GeCl2·dioxane with 2 equiv of the thiolate LiSHyp [Hyp = Si(SiMe3)3] yields the germanide (12-crown-4)2Li[Ge(SHyp)3] (1). A small structural variation in the substituent leads to a completely different result because the reaction of GeCl2·dioxane with 2 equiv of the thiolate KSHypPh3 [HypPh3 = Si(SiMe3)2(SiPh3)] in toluene yields the unexpected compound [Ph3Si][Me3Si]Ge[{(C6H5)Ph2Si}{SiMe3}2SiS]Si[SSiMe3] (2) in high yield. The reaction cascade to give 2 includes several rearrangement reactions and an intramolecular [2 + 4] cycloaddition of a phenyl ring. The syntheses and molecular structures of both compounds are presented, together with quantum-chemical calculations and NMR measurements, to enlighten the reaction mechanism behind the formation of 2.

Photoexcitation of Ge9- Clusters in THF: New Insights into the Ultrafast Relaxation Dynamics and the Influence of the Cation.

We present a comprehensive femtosecond (fs) transient absorption study of the [Ge9(Hyp)3]- (Hyp = Si(SiMe3)3) cluster solvated in tetrahydrofuran (THF) with special emphasis on intra- and intermolecular charge transfer mechanisms which can be tuned by exchange of the counterion and by dimerization of the cluster. The examination of the visible and the near infrared (NIR) spectral range reveals four different processes of cluster dynamics after UV (267/258 nm) photoexcitation related to charge transfer to solvent and localized excited states in the cluster. The resulting transient absorption is mainly observed in the NIR region. In the UV-Vis range transient absorption of the (neutral) cluster core with similar dynamics can be observed. By transferring concepts of: (i) charge transfer to the solvent known from solvated Na- in THF and (ii) charge transfer in bulk-like materials on metalloid cluster systems containing [Ge9(Hyp)3]- moieties, we can nicely interpret the experimental findings for the different compounds. The first process occurs on a fs timescale and is attributed to localization of the excited electron in the quasi-conduction band/excited state which competes with a charge transfer to the solvent. The latter leads to an excess electron initially located in the vicinity of the parent cluster within the same solvent shell. In a second step, it can recombine with the cluster core with time constants in the picosecond (ps) timescale. Some electrons can escape the influence of the cluster leading to a solvated electron or after interaction with a cation to a contact pair both with lifetimes exceeding our experimentally accessible time window of 1 nanosecond (ns). An additional time constant on a tens of ps timescale is pronounced in the UV-Vis range which can be attributed to the recombination rate of the excited state or quasi conduction band of Ge9-. In the dimer, the excess electron cannot escape the molecule due to strong trapping by the Zn cation that links the two cluster cores.

Synthesis and Characterization of the Highly Unstable Metalloid Cluster Ag64 (Pn Bu3 )16 Cl6.

The reduction of (n Bu3 P)AgCl with LiBH(s Bu)3 in toluene gives the metalloid silver cluster Ag64 (Pn Bu3 )16 Cl6 (1) as dark red, temperature- and light-sensitive single crystals in high yield. 1 is the largest structurally characterized metalloid silver cluster exhibiting chlorine and phosphine substituents only. The silver atoms in 1 show an overall brick-shape arrangement, where structural resemblance to the close-packed fcc and hcp structures is realized. Within 1 a 58 electron closed shell system is present. The light sensitivity renders 1 as a model compound for the primary seeds of the photo process, whereby this sensitivity, together with the high-yield synthesis show that 1 is a perfect starting compound for further investigations like silver-plating processes.

Halides of the Heavier Group†14 Homologues Germanium, Tin, and Lead-A Journey through Unusual Compounds and Oxidation States.

Classical halides of the heavier Group 14 homologues germanium, tin, and lead are common precursors for the synthesis of exciting compounds, such as polyhedral clusters. To get access to larger metalloid cluster compounds of Group 14, the disproportionation reaction of metastable monohalide solutions, accessible through a preparative co-condensation reaction, proved to be quite successful. As the identity of the subvalent halides within the metastable solutions were yet unknown the reaction course from a monohalide precursor to a metalloid cluster was mostly unidentified. This might change now, as a first subhalide cluster [Ge14 Br8 (Et3 P)4 ] could be characterized, being the first trapped intermediate of the disproportionation reaction of Group 14 subhalides. All these aspects are included within this Minireview, together with a short historical overview, dealing with the development of the preparative co-condensation technique out of the matrix isolation technique, being the essential first step of the synthesis of metastable monohalide solutions of the heavier Group 14 elements Ge and Sn.

Reactions of GeCl2 with the Thiolate LiSC(SiMe3 )3 : From thf Activation to Insertion of GeCl2 Molecules into C-S Bonds.

The reaction system GeCl2 ⋅dioxane/LiSTsi (Tsi=C(SiMe3 )3 ) opens a fruitful area in germanium chemistry, depending on the stoichiometry and solvent used during the reaction. For example, the reaction of GeCl2 ⋅dioxane in toluene with two equivalents of the thiolate gives the expected germylene Ge(STsi)2 in excellent yield. This germylene readily reacts with hydrogen and acetylene, however, in a non-selective way. By using an excess amount of the thiolate and toluene as the solvent, the germanide [Ge(STsi)3 ][Li(thf)] is obtained. Performing the same reaction in thf leads to a C-H activation of thf to give (H7 C4 O)Ge[STsi](µ2 -S)2 Ge[STsi]2 , in which the thf molecule is still intact. Using a sub-stoichiometric amount of the thiolate leads to the heteroleptic compound [ClGe(STsi)]2 and to the insertion product (thf)Ge[S-GeCl2 -Tsi]2 , in which additional GeCl2 molecules insert into the C-S bonds of Ge(STsi)2 . The synthesis and the experimentally determined structures of all compounds are presented together with first reactivity studies of Ge(STsi)2 .

Synthesis and Photodimerization of 2- and 2,3-Disubstituted Anthracenes: Influence of Steric Interactions and London Dispersion on Diastereoselectivity.

There is increased evidence that the effect of bulky groups in organic, organometallic, and inorganic chemistry is not only repulsive but can be attractive because of London dispersion interactions. The influence of the size of primary alkyl substituents in 2- and 2,3-positions of anthracenes on the diastereoselectivity (anti vs syn dimer) of the [π4s + π4s] photoinduced dimerization is investigated. The synthesis of the anthracene derivatives was achieved by Suzuki-Miyaura reaction of 2,3-dibromoanthracene with alkylboronic acids as well as by reduction of anthraquinones that were obtained from 2,3-disubstituted 1,3-butadienes and naphthoquinone followed by dehydrogenation. The mixtures of dianthracene isomers were analyzed with respect to the anti/syn-ratio of the products by X-ray crystallography and nuclear Overhauser effect spectroscopy. While for the 2,3-dimethylanthracene the anti and syn isomers were formed in equal amounts, the anti dimers are the major products in all other cases. A linear correlation (R2 = 0.98) between the steric size (Charton parameter) and the isomeric ratio suggests that the selectivity is dominated by classical repulsive steric effects. An exception is the iso-butyl substituent that produces an increased amount of the syn isomer. It is suggested that this is due to an exalted effect of London dispersion interactions.

Synthesis and Characterization of Three Multi-Shell Metalloid Gold Clusters Au32 (R3 P)12 Cl8.

Three multi-shell metalloid gold clusters of the composition Au32 (R3 P)12 Cl8 (R=Et, n Pr, n Bu) were synthesized in a straightforward fashion by reducing R3 PAuCl with NaBH4 in ethanol. The Au32 core comprises two shells, with the inner one constituting a tilted icosahedron and the outer one showing a distorted dodecahedral arrangement. The outer shell is completed by eight chloride atoms and twelve R3 P groups. The inner icosahedron shows bond lengths typical for elemental gold while the distances of the gold atoms in the dodecahedral arrangement are in the region of aurophilic interactions. Quantum-chemical calculations illustrate that the Jahn-Teller effect observed within the cluster core can be attributed to the electronic shell filling. The easily reproducible synthesis, good solubility, and high yields of these clusters render them perfect starting points for further research.

[PtZn2Ge18(Hyp)8] (Hyp = Si(SiMe3)3): A Neutral Polynuclear Chain Compound with Ge9(Hyp)3 Units.

The reaction of [ZnGe18(Hyp)6] (Hyp = Si(SiMe3)3) with Pt(PPh3)4 gives the neutral polynuclear complex of Ge9(Hyp)3 units [HypZn-Ge9(Hyp)3-Pt-Ge9(Hyp)3-ZnHyp], 1. Within 1, the central Pt atom is bound η3 to both Ge9(Hyp)3 units to which further ZnHyp units are bound again, symmetric η3, to the other side of the Ge9(Hyp)3 units, leading to the longest chain compound exhibiting Ge9(Hyp)3 units that is known to date. Dissolved crystals of 1 give a violet solution, showing an absorption maximum around 543 nm. Further UV-vis investigations on different M xGe9(Hyp)3 compounds show that the absorption maximum depends on the number of transition metal atoms bound to the Ge9(Hyp)3 unit, which is supported by TD-DFT calculations.