Regio- and chemoselective catalytic partial transfer hydrogenation of quinolines by dinuclear aluminum species.

Catalytic reduction of quinolines has gained continuous interest in both academia and industry, providing direct and efficient access to tetrahydroquinolines or 1,2-dihydroquinolines. The catalytic preparation of tetrahydroquinolines has been extensively studied by transition metal complexes. By contrast, the related catalytic synthesis of 1,2-dihydroquinolines remains underdeveloped due to the difficulties in achieving precise control over both chemo- and regioselectivity.

Reversible CO Insertion into the Si = Si Double Bond Enables a Disila-Bislactone Formation via Subsequent CO Addition.

Carbon monoxide inserts into the Si═Si double bond of an imino(silyl)disilene and tetra(silyl)disilene affording the corresponding 1,3-disilaallene oxides, characterized by NMR spectroscopy and X-ray crystallography and supported by quantum chemical calculations. In the case of imino(silyl)disilene, the CO insertion is less exergonic than for tetrasilyldisilene and, thus, is fully reversible in the presence of a CO trapping agent. The reaction mechanisms and reversibility facilitated by the imino-substituent were supported by quantum chemical calculations.

Utilization of a Chelating Bis[(dialkylamino)cyclopropenimine] to Isolate a Series of Heavier Zero-Valent Group 14 Tetracarbonyl Iron Complexes.

We report on the utilization of the ethylene-bridged bis[(dialkylamino)cyclopropenimine] (bisCPI) ligand, L, to give access to new main-group E(II) halide complexes (E = Ge, Sn, Pb; 1, 2, 3). Subsequent reduction with Collman's reagent (NaFe(CO) • dioxane) enables the isolation of a series of zero-valent tetrylone-tetracarbonyl iron complexes, (L)E(Fe(CO) (E = Ge (4), Sn (5), Pb (6)). Compounds 4 - 6 were reacted further with iron pentacarbonyl to yield the bis-tetracarbonyl iron complexes (L)E[(Fe(CO)] (E = Ge (7), Sn (8), Pb (9)).

The Substituent-Effect in NHCP-Plumbylenes with a Phosphaplumbene Character.

This work explores the use of plumbylene-phosphinidenes to address the challenge of isolating P=Pb bonds. Herein, we report the synthesis of three N-heterocyclic carbene phosphinidene (NHCP) substituted chlorotetrylene dimers [(IDipp)PECl] (E=Ge, Sn, Pb; IDipp=C([N-(2,6-Pr-CH)CH])). Substituent attachment via salt metathesis (E=Sn, Pb) enables the isolation of NHCP-silyl-substituted stannylene (IDipp)PSn(SiTmsSiTol) as well as NHCP-silyl- and NHCP-aryl-substituted plumbylenes (IDipp)PPb(SiTmsSiTol) and (IDipp)PPb(Ter) (Ter=2,6-MesCH, Tms=Trimethylsilyl).

CO hydrosilylation catalyzed by an N-heterocyclic carbene (NHC)-stabilized stannyliumylidene.

The di-N-heterocyclic carbene (NHCs) stabilized stannyliumylidene, [TerSn(IMe)][BArF], (Ter = 2,6-MesCH, Mes = 2,4,6-Me-CH, IMe = 1,3,4,5-tetramethylimidazol-2-ylidene, BArF = (3,5-(CF)-CH)B), was isolated from the reaction of (Ter)SnCl with two equivalents of IMe, followed by one equivalent of Na[BArF]. This stannyliumylidene acts as a precatalyst for the homogeneous hydrosilylation of CO. Experimental mechanistic studies and quantum chemical calculations have been conducted to elucidate the catalytically active species and the mechanism for the transformation, revealing the stannyliumylidene [TerSn(COIMe)][BArF], which is formed in the presence of CO, as the catalytically active species.

Self-Foldable Three-Dimensional Biointerfaces by Strain Engineering of Two-Dimensional Layered Materials on Polymers.

Two-dimensional layered materials (2DLMs) have received increasing attention for their potential in bioelectronics due to their favorable electrical, optical, and mechanical properties. The transformation of the planar structures of 2DLMs into complex 3D shapes is a key strategic step toward creating conformal biointerfaces with cells and applying them as scaffolds to simultaneously guide their growth to tissues and enable integrated bioelectronic monitoring. Using a strain-engineered self-foldable bilayer, we demonstrate the facile formation of predetermined 3D microstructures of 2DLMs with controllable curvatures, called microrolls.

Stereoselective Sequential Diels-Alder Reactions on a Cyclic Furan Trimer for the Construction of an Asymmetric Scaffold.

Multiple Diels-Alder reactions are a powerful method to construct large asymmetric scaffolds, but these reactions often produce numerous isomers. We now report a triple Diels-Alder reaction between a cyclic furan trimer and -substituted maleimides, achieving selective synthesis of a single asymmetric tris-adduct. The stereoselectivity of cycloaddition to π-extended furan derivatives was clarified by the experimental analysis of intermediates and theoretical calculations.

Silicon-aryl cooperative activation of ammonia.

Herein, we report the reactivity of N-heterocyclic carbene stabilized silylene-phosphinidene IDippPSi(TMS)SiTol (IDipp = 1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene) with ammonia, which results in an intermolecular 1,5-hydroamination and dearomatization of the NHC wingtip. DFT calculations reveal an unprecedented mechanism involving ammonia coordination to the silicon center, Meisenheimer-type complex formation, and a proton abstraction by the dearomatized aryl moiety.

Isolation of a NHC-stabilized heavier nitrile and its conversion into an isonitrile analogue.

Nitriles (R-C≡N) have been investigated since the late eighteenth century and are ubiquitous encounters in organic and inorganic syntheses. In contrast, heavier nitriles, which contain the heavier analogues of carbon and nitrogen, are sparsely investigated species. Here we report the synthesis and isolation of a phosphino-silylene featuring an N-heterocyclic carbene-phosphinidene and a highly sterically demanding silyl group as substituents.

Dialumene as a Dimeric or Monomeric Al Synthon for C-F Activation in Monofluorobenzene.

The activation of C-F bonds has long been regarded as the subject of research in organometallic chemistry, given their synthetic relevance and the fact that fluorine is the most abundant halogen in the Earth's crust. However, C-F bond activation remains a largely unsolved challenge due to the high bond dissociation energies, which was historically dominated by transition metal complexes. Main group elements that can cleave unactivated monofluorobenzene are still quite rare and restricted to s-block complexes with a biphilic nature.

(SiFA)SeFe: A Hydrophilic Silicon-Based Fluoride Acceptor Enabling Versatile Peptidic Radiohybrid Tracers.

The radiohybrid (rh) concept to design targeted (and chemically identical) radiotracers for imaging or radionuclide therapy of tumors has gained momentum. For this strategy, a new bifunctional Silicon-based Fluoride Acceptor (SiFA) moiety was synthesized, endowed with improved hydrophilicity and high versatility of integration into rh-compounds. Preliminary radiolabeling and stability studies under different conditions were conducted using model bioconjugate peptides.

A neutral crystalline imino-substituted silyl radical.

The neutral three-coordinated imino(silyl)silyl radical was isolated from the reaction of N-heterocyclic iminosilicon tribromide (IBuN-SiBr) with NaSiBuMe. The radical was fully characterized by X-ray crystallography and electron paramagnetic resonance spectroscopy and supported by quantum chemical calculations.

Tetryliumylidene ions in synthesis and catalysis.

Tetryliumylidene ions ([R-E:]), recognised for their intriguing electronic properties, have attracted considerable interest. These positively charged species, with two vacant p-orbitals and a lone pair at the E(ii) centre (E = Si, Ge, Sn, Pb), can be viewed as the combination of tetrylenes (RE:) and tetrylium ions ([RE]), which makes them potent Lewis ambiphiles. Such electronic features highlight the potential of tetryliumylidenes for single-site small molecule activation and transition metal-free catalysis.

Synthesis and reactivity of N-heterocyclic carbene (NHC)-supported heavier nitrile ylides.

The synthesis and isolation of stable heavier analogues of nitrile ylide as N-heterocyclic carbene (NHC) adducts of phosphasilenyl-tetrylene [(NHC)(Ar)Si(H)PE(Ar)] (E = Ge 1, Sn 2; Ar = 2,6-MesCH, NHC = IMe) are reported. The delocalized Si-P-E π-conjugation was examined experimentally and computationally. Interestingly, the germanium derivative 1 exhibits a 1,3-dipolar nature, leading to an unprecedented [3 + 2] cycloaddition with benzaldehyde, resulting in unique heterocycles containing four heteroatoms from group 14, 15, and 16.

A neutral germanium-centred hard and soft lewis superacid and its unique reactivity towards hydrosilanes.

The germanium-centred Lewis superacid Ge(pin) (1) was isolated as acetonitrile mono-adduct 1·MeCN and thoroughly characterized by NMR spectroscopy, X-ray crystallography and quantum chemical calculations. Ion abstraction and NMR experiments revealed the hard as well as soft Lewis superacidic nature of 1·MeCN. The title compound readily activates hydrosilanes such as EtSiH, which is not feasible for its harder silicon homologue 2·MeCN, and even reacts with EtSiF.

Reactivity of NHI-Stabilized Heavier Tetrylenes towards CO and N O.

A heteroleptic amino(imino)stannylene (TMS N)(I BuN)Sn: (TMS=trimethylsilyl, I Bu=C[(N- Bu)CH] ) as well as two homoleptic NHI-stabilized tetrylenes, (I BuN) E: (NHI=N-heterocyclic imine, E=Ge, Sn) are presented. VT-NMR investigations of (I BuN) Sn: (2) reveal an equilibrium between the monomeric stannylene at room temperature and the dimeric form at -80 °C as well as in the solid state. Upon reaction of the homoleptic tetrylenes with CO , both compounds insert two equivalents of CO , however differing bonding modes can be observed.

Potent Anticancer Activity of a Dinuclear Gold(I) bis-N-Heterocyclic Imine Complex Related to Thioredoxin Reductase Inhibition in Vitro.

A dinuclear gold(I) complex featuring a strongly donating bis-N-heterocyclic imine ligand was synthesised and characterised by different methods, including single crystal X-ray diffraction (SC-XRD) analysis. The compound has been tested for its antiproliferative effects in a panel of human cancer cell lines in vitro, showing highly selective anticancer effects, particularly against human A549 non-small cell lung cancer cells (NSCLC), with respect to non-tumorigenic cells (VERO). The accumulation of the compound in A549 and VERO cells was studied by high-resolution continuum source atomic absorption spectrometry (HRCS-AAS), revealing that the anticancer effects are not particularly related to the different amounts of gold taken up by the cells over 72 h.

Dearomatization of C Aromatic Hydrocarbons by Main Group Complexes.

The dearomatization reaction is a powerful method for transformation of simple aromatic compounds to unique chemical architectures rapidly in synthetic chemistry. Over the past decades, the chemistry in this field has evolved significantly and various important organic compounds such as crucial bioactive molecules have been synthesized through dearomatization. In general, photochemical conditions or assistance by transition metals are required for dearomatization of rigid arenes.

Anions featuring an aluminium-silicon core with alumanyl silanide and aluminata-silene characteristics.

Molecular species containing multiple bonds to aluminium have long been challenging synthetic targets. Despite recent landmark discoveries in this area, heterodinuclear Al-E multiple bonds (where E is a group-14 element) have remained rare and limited to highly polarized π-interactions (Al=E ↔ Al-E). Here we report the isolation of three alumanyl silanide anions that feature an Al-Si core stabilized by bulky substituents and a Si-Na interaction.

An Aluminum Telluride with a Terminal Al=Te Bond and its Conversion to an Aluminum Tellurocarbonate by CO Reduction.

Facile access to dimeric heavier aluminum chalcogenides [(NHC)Al(Tipp)-μ-Ch] (NHC=IiPr (1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene, IMe (1,3,4,5-tetramethylimidazol-2-ylidene); Tipp=2,4,6-iPr C H ; Ch=Se, Te) by treatment of NHC-stabilized aluminum dihydrides with elemental Se and Te is reported. The higher affinity of IMe in comparison with IiPr toward the Al center in [(NHC)Al(Tipp)-μ-Ch] can be used for ligand exchange. Additionally, the presence of excess IMe allows for cleavage of the dimers to form a rare example of a neutral multiply bonded heavier aluminum chalcogenide in the form of a tetracoordinate aluminum complex, (IMe ) (Tipp)Al=Te.

Room Temperature Intermolecular Dearomatization of Arenes by an Acyclic Iminosilylene.

A novel nontransient acyclic iminosilylene (), bearing a bulky super silyl group (-SiBu) and -heterocyclic imine ligand with a methylated backbone, was prepared and isolated. The methylated backbone is the feature of that distinguishes it from the previously reported nonisolable iminosilylenes, as it prevents the intramolecular silylene center insertion into an aromatic C-C bond of an aryl substituent. Instead, exhibits an intermolecular Büchner-ring-expansion-type reactivity; the silylene is capable of dearomatization of benzene and its derivatives, giving the corresponding silicon analogs of cycloheptatrienes, .

Photo-Activity of Silacyclopropenes and their Application in Metal-Free Curing of Silicones.

Silicone elastomers are usually produced via addition or condensation curing by means of platinum- or tin-based catalysis. The employed catalysts remain in the final rubber and cannot be recovered, thus creating various economic and environmental challenges. Herein, a light-mediated curing method using multifunctional silacyclopropenes as crosslinker structures was introduced to create an effective alternative to the conventional industrial crosslinking.

Isolation and Reactivity of Stannylenoids Stabilized by Amido/Imino Ligands.

The reaction of the lithium aryl(silyl)amide Dipp( Pr Si)NLi (Dipp=2,6- Pr C H ) with one equivalent of SnCl in THF gave a novel stannylenoid Dipp( Pr Si)NSnCl⋅LiCl(THF) . Heating the solution of amidostannylenoid in toluene to 80 °C resulted in dimeric amido(chloro)stannylene [Dipp( Pr Si)NSnCl] , which can be converted to bis(amido)stannylene Sn[N(Dipp)( Pr Si)] and amido(imino)stannylene Sn[N(Dipp)( Pr Si)][IPrN] (IPrN=bis(2,6-diisopropylphenyl)imidazolin-2-imino). Treatment of bis(imino)stannylenoid [IPrN] Sn(Cl)Li with N O resulted in the dimeric complex [IPrNSn(Cl)OLi] .