Unprecedented Insertion Research Articles

Bimetallic Synergy Enables Silole Insertion into THF and the Synthesis of Erbium Single‐Molecule Magnets

AbstractThe potassium silole K2[SiC4‐2,5‐(SiMe3)2‐3,4‐Ph2] reacts with [M(η8‐COT)(THF)4][BPh4] (M=Er, Y; COT=cyclo‐octatetraenyl) in THF to give products that feature unprecedented insertion of the nucleophilic silicon centre into a carbon‐oxygen bond of THF. The structure of the major product, [(μ‐η8 : η8‐COT)M(μ‐L1)K]∞ (1M), consists of polymeric chains of sandwich complexes, where the spiro‐bicyclic silapyran ligand [C4H8OSiC4(SiMe3)2Ph2]2− (L1) coordinates to potassium via the oxygen. The minor product [(μ‐η8 : η8‐COT)M(μ‐L1)K(THF)]2 (2M) features coordination of the silapyran to the rare‐earth metal. In forming 1M and 2M, silole insertion into THF only occurs in the presence of potassium and the rare‐earth metal, highlighting the importance of bimetallic synergy. The lower nucleophilicity of germanium(II) leads to contrasting reactivity of the potassium germole K2[GeC4‐2,5‐(SiMe3)2‐3,4‐Me2] towards [M(η8‐COT)(THF)4][BPh4], with intact transfer of the germole occurring to give the coordination polymers [{η5‐GeC4(SiMe3)2Me2}M(η8‐COT)K]∞ (3M). Despite the differences in reactivity induced by the group 14 heteroatom, the single‐molecule magnet properties of 1Er, 2Er and 3Er are similar, with thermally activated relaxation occurring via the first‐excited Kramers doublet, subject to effective energy barriers of 122, 80 and 91 cm−1, respectively. Compound 1Er is also analysed by high‐frequency dynamic magnetic susceptibility measurements up to 106 Hz.

Bimetallic Synergy Enables Silole Insertion into THF and the Synthesis of Erbium Single-Molecule Magnets.

The potassium silole K2 [SiC4 -2,5-(SiMe3 )2 -3,4-Ph2 ] reacts with [M(η8 -COT)(THF)4 ][BPh4 ] (M=Er, Y; COT=cyclo-octatetraenyl) in THF to give products that feature unprecedented insertion of the nucleophilic silicon centre into a carbon-oxygen bond of THF. The structure of the major product, [(μ-η8 : η8 -COT)M(μ-L1 )K]∞ (1M ), consists of polymeric chains of sandwich complexes, where the spiro-bicyclic silapyran ligand [C4 H8 OSiC4 (SiMe3 )2 Ph2 ]2- (L1 ) coordinates to potassium via the oxygen. The minor product [(μ-η8 : η8 -COT)M(μ-L1 )K(THF)]2 (2M ) features coordination of the silapyran to the rare-earth metal. In forming 1M and 2M , silole insertion into THF only occurs in the presence of potassium and the rare-earth metal, highlighting the importance of bimetallic synergy. The lower nucleophilicity of germanium(II) leads to contrasting reactivity of the potassium germole K2 [GeC4 -2,5-(SiMe3 )2 -3,4-Me2 ] towards [M(η8 -COT)(THF)4 ][BPh4 ], with intact transfer of the germole occurring to give the coordination polymers [{η5 -GeC4 (SiMe3 )2 Me2 }M(η8 -COT)K]∞ (3M ). Despite the differences in reactivity induced by the group 14 heteroatom, the single-molecule magnet properties of 1Er , 2Er and 3Er are similar, with thermally activated relaxation occurring via the first-excited Kramers doublet, subject to effective energy barriers of 122, 80 and 91 cm-1 , respectively. Compound 1Er is also analysed by high-frequency dynamic magnetic susceptibility measurements up to 106 Hz.

Towards (C,C)‐cyclometalated N‐(9‐alkylfluorenyl)NHC Ruthenium Complexes for Z‐selective Olefin Metathesis

AbstractThree Hoveyda‐Grubbs complexes supported by N‐(9‐alkylfluorenyl)imidazol‐2‐ylidene ligands (alkyl=methyl, ethyl or benzyl) have been synthesized. With the aim to generate chelating, cyclometalated (C,CNHC) ruthenium complexes for Z‐selective olefin metathesis, the C(sp3)‐H activation of the dangling alkyl group has been studied. While the methyl derivative leads to the expected cyclometalated complex, a C(sp2)‐H activation of the fluorenyl moiety and no evolution/transformation are observed for the ethyl and benzyl derivatives, respectively. Although highly fragile under catalytic conditions, the cyclometalated complex leads to Z/E stereoselectivity up to 94/6. An unprecedented insertion of the alkylidene moiety into the Ru‐CNHC bond leading to ruthenium N‐heterocyclic olefin complexes is also observed and supported by calculations of the corresponding reaction pathway.

Conversion of a AuI Fluorido Complex into an N‐Fluoroamido Derivative: N−F versus Au−N Reactivity

AbstractThe AuI complex [Au{N(F)SO2Ph}(SPhos)] (SPhos=dicyclohexyl(2′,6′‐dimethoxy[1,1′‐biphenyl]‐2‐yl)phosphane) (2) bearing a fluoroamido ligand has been synthesized by reaction of the fluorido complex [Au(F)(SPhos)] (1) with NFSI (NFSI=N‐fluorobenzenesulfonimide). A reaction with CO resulted in an unprecedented insertion into the N−F bond at 2. With the carbene precursor N2CH(CO2Et) N−F bond cleavage gave the Au−F bond insertion product [Au{CHF(CO2C2H5)}(SPhos)] (7). The presence of CNtBu led to Au−N cleavage at 2 and concomitant amide formation to give the cationic complex [Au(CNtBu)(SPhos)][N(F)SO2Ph)] (5), which reacted further to give FtBu as well as the cyanido complex [Au(CN)(SPhos)] (6). These results led to the development of a process for the amination of electrophilic organic substrates by transfer of the fluoroamido group NF(SO2Ph)−.

Conversion of a AuI Fluorido Complex into an N-Fluoroamido Derivative: N-F versus Au-N Reactivity.

The AuI complex [Au{N(F)SO2 Ph}(SPhos)] (SPhos=dicyclohexyl(2',6'-dimethoxy[1,1'-biphenyl]-2-yl)phosphane) (2) bearing a fluoroamido ligand has been synthesized by reaction of the fluorido complex [Au(F)(SPhos)] (1) with NFSI (NFSI=N-fluorobenzenesulfonimide). A reaction with CO resulted in an unprecedented insertion into the N-F bond at 2. With the carbene precursor N2 CH(CO2 Et) N-F bond cleavage gave the Au-F bond insertion product [Au{CHF(CO2 C2 H5 )}(SPhos)] (7). The presence of CNtBu led to Au-N cleavage at 2 and concomitant amide formation to give the cationic complex [Au(CNtBu)(SPhos)][N(F)SO2 Ph)] (5), which reacted further to give FtBu as well as the cyanido complex [Au(CN)(SPhos)] (6). These results led to the development of a process for the amination of electrophilic organic substrates by transfer of the fluoroamido group NF(SO2 Ph)- .

Spoof Surface Plasmon Polariton Delay Lines for Terahertz Phase Shifters

The terahertz gap attracted interest of researchers with its captivating properties such as its potential for ultrawideband communication and high-resolution imaging applications, which require robust and efficient terahertz components and circuits. Terahertz spoof surface plasmon polaritons are perfect alternatives to implement terahertz integrated circuits. We present the first-time demonstration of the terahertz spoof surface plasmon polariton delay lines for terahertz phase shifters, which present an unprecedented insertion phase versus loss performance. The electrical lengths of the proposed delay lines are tuned just by changing the corrugation depths, which allows the designer to keep the physical length of the delay lines constant. In order to verify the proposed idea, four different delay lines having the same length of 1052.5 μm are designed, where the electrical lengths of the delay lines are selected to represent the four different phase states of a 2-bit phase shifter. The measurement results of the fabricated terahertz delay lines show almost perfect phase accuracy and very good agreement with the simulations, having an ultra-low average phase error of 0.6%, and average insertion and return losses of −2.3 and −18 dB, respectively. These measurements result in, to the best of our knowledge, a record-high figure-of-merit of 90°/dB compared to all other kinds of planar waveguides at 0.3 THz. The proposed delay lines emerge as a very high-performance and promising candidate for all the waveguide-based components that are crucial for the terahertz integrated circuits.

Fragmentation, catenation, and direct functionalisation of white phosphorus by a uranium(IV)-silyl-phosphino-carbene complex.

Room temperature reaction of the uranium(iv)-carbene [U{C(SiMe3)(PPh2)}(BIPMTMS)(μ-Cl)Li(TMEDA)(μ-TMEDA)0.5]2 (1, BIPMTMS = C(PPh2NSiMe3)2) with white phosphorus (P4) produces the organo-P5 compound [P5{C(SiMe3)(PPh2)}2][Li(TMEDA)2] (2) and the uranium(iv)-methanediide [U{BIPMTMS}{Cl}{μ-Cl}2{Li(TMEDA)}] (3). This is an unprecedented example of cooperative metal-carbene P4 activation/insertion into a metal-carbon double bond and also an actinide complex reacting with P4 to directly form an organophosphorus species. Conducting the reaction at low temperature permits the isolation of the diuranium(iv) complex [{U(BIPMTMS)([μ-η2:η2-P2]C[SiMe3][PPh2])}2] (4), which then converts to 2 and 3. Thus, surprisingly, in contrast to all other actinide P4 reactivity, although this reaction produces catenation overall it proceeds via P4 cleavage to functionalised P2 units. Hence, this work establishes a proof of concept synthetic cycle for direct fragmentation, catenation, and functionalisation of P4.

Towards a better understanding of the low recall of insertion variants with short-read based variant callers

BackgroundSince 2009, numerous tools have been developed to detect structural variants using short read technologies. Insertions >50 bp are one of the hardest type to discover and are drastically underrepresented in gold standard variant callsets. The advent of long read technologies has completely changed the situation. In 2019, two independent cross technologies studies have published the most complete variant callsets with sequence resolved insertions in human individuals. Among the reported insertions, only 17 to 28% could be discovered with short-read based tools.ResultsIn this work, we performed an in-depth analysis of these unprecedented insertion callsets in order to investigate the causes of such failures. We have first established a precise classification of insertion variants according to four layers of characterization: the nature and size of the inserted sequence, the genomic context of the insertion site and the breakpoint junction complexity. Because these levels are intertwined, we then used simulations to characterize the impact of each complexity factor on the recall of several structural variant callers. We showed that most reported insertions exhibited characteristics that may interfere with their discovery: 63% were tandem repeat expansions, 38% contained homology larger than 10 bp within their breakpoint junctions and 70% were located in simple repeats. Consequently, the recall of short-read based variant callers was significantly lower for such insertions (6% for tandem repeats vs 56% for mobile element insertions). Simulations showed that the most impacting factor was the insertion type rather than the genomic context, with various difficulties being handled differently among the tested structural variant callers, and they highlighted the lack of sequence resolution for most insertion calls.ConclusionsOur results explain the low recall by pointing out several difficulty factors among the observed insertion features and provide avenues for improving SV caller algorithms and their combinations.

S-Aryl Arenesulfonothioate and Copper Acetate Mediated Arylthiolation of 2-Arylpyridines and Heteroarenes.

Copper acetate mediated regioselective ortho-arylthiolation of 2-arylpyridines has been accomplished for the first time using S-aryl arenesulfonothioate as the arylthiolating agent. The reaction shows good functional group tolerance and gives thioarylated products in 67-89% yields. This reagent is a good alternative to unpleasant smelling arylthiols. Experimental evidence suggests an unprecedented insertion of an arylthio unit from both parts of the reagent (SPh and p-TolSO2) in the presence of copper acetate. Indoles and imidazopyridines also undergo facile reaction at the C-3 position and furnish thioarylated derivatives in good yields.

Selective Carbon–Carbon Bond Activation of Epoxides by a Bisphosphine Pt(0) Complex

Contrasting established bond activation chemistry of oxiranes (epoxides), the unprecedented insertion of a Pt(0) complex into the carbon–carbon bonds of ethylene oxide and other epoxides, generating 3-oxaplatinacyclobutanes under remarkably mild conditions, has been found. Pt(II) neopentyl hydride complex (dtbpm-κ2P)Pt(Np)H (1) undergoes first-order reductive elimination of neopentane at ambient temperature in solution, forming a highly reactive species of an overall composition [(dtbpm)Pt(0)] (C). This intermediate inserts into epoxide C–C bonds or, in the absence of substrates, dimerizes to d10–d10 Pt(0) species D. The epoxide activation products have been fully characterized including X-ray structure determinations. Various experiments have been conducted in order to decipher mechanistic details of this unusual chemistry. Theoretical studies on various levels do not allow a reliable conclusion as to the actual nature of the reactive intermediate C. Both conceivable structures C1 (ring-opened [(dtbpm-κ1P)Pt(0), d10-ML, 12 VE]) and C2 (chelate, [(dtbpm-κ2P)Pt(0)], d10-ML2, 14 VE) are minimum-energy structures with a very small (method-dependent) energy difference.

α-Thiocarbonyl synthesis via the FeII-catalyzed insertion reaction of α-diazocarbonyls into S-H bonds.

Fe(OTf)2 was used to catalyze the insertion reaction of α-diazocarbonyls into S-H bonds at 40 °C. A wide range of α-thioesters were obtained in yields up to 96% within 24-48 h from their corresponding α-diazoesters. A variety of thiols were used for the unprecedented insertion reaction with an α-diazoketone, leading to yields up to 85% of α-thioketones.

Gold-Nanoparticle-Catalyzed Silaboration of Oxetanes and Unactivated Epoxides

Supported gold nanoparticles catalyze the unprecedented insertion of a silylborane into the C–O bond of oxetanes and unactivated epoxides, forming γ- or β-silyloxy boronates in good to excellent yields. In the silaboration process the boron moiety is acting as a nucleophile and the silyl as an electrophile. No external additives or ligands are required, while the catalytic system is recyclable and reusable.

Noncanoncial signal recognition particle RNAs in a major eukaryotic phylum revealed by purification of SRP from the human pathogen Cryptococcus neoformans.

Despite conservation of the signal recognition particle (SRP) from bacteria to man, computational approaches have failed to identify SRP components from genomes of many lower eukaryotes, raising the possibility that they have been lost or altered in those lineages. We report purification and analysis of SRP in the human pathogen Cryptococcus neoformans, providing the first description of SRP in basidiomycetous yeast. The C. neoformans SRP RNA displays a predicted structure in which the universally conserved helix 8 contains an unprecedented stem-loop insertion. Guided by this sequence, we computationally identified 152 SRP RNAs throughout the phylum Basidiomycota. This analysis revealed additional helix 8 alterations including single and double stem-loop insertions as well as loop diminutions affecting RNA structural elements that are otherwise conserved from bacteria to man. Strikingly, these SRP RNA features in Basidiomycota are accompanied by phylum-specific alterations in the RNA-binding domain of Srp54, the SRP protein subunit that directly interacts with helix 8. Our findings reveal unexpected fungal SRP diversity and suggest coevolution of the two most conserved SRP features—SRP RNA helix 8 and Srp54—in basidiomycetes. Because members of this phylum include important human and plant pathogens, these noncanonical features provide new targets for antifungal compound development.

Uptake of CO2 in Layered P2-Na0.67Mn0.5Fe0.5O2: Insertion of Carbonate Anions

Batteries based on sodium layered transition metal oxides are a promising alternative to current state-of-the-art lithium-ion systems for large-scale energy storage, resulting in recent intensive efforts to develop high-energy density, low cost, stable cathode materials. Some of the most promising degrade on exposure to ambient atmosphere; however, the process is not understood. Here, using neutron/X-ray diffraction coupled with mass spectroscopy and thermal analysis, we reveal the nature of the reactivity. We demonstrate the unprecedented insertion of carbonate ions in the vacancy-rich layered structure of P2-Na0.67[Mn0.5Fe0.5]O2 on exposure to CO2 and moisture, concomitant with oxidation of Mn(III) to Mn(IV). The material exhibits much higher charge/discharge polarization and lower capacity than rigorously air-protected P2-Na0.67[Mn0.5Fe0.5]O2; a detailed study by online electrochemistry mass spectroscopy reveals that the inserted carbonate ions decompose during electrochemical charging, accounting for ...

Dual Gold Catalysis: Synthesis of Polycyclic Compounds via CH Insertion of Gold Vinylidenes

New and interesting polycyclic compounds have been synthesized from non-conjugated diyne systems by dual gold catalysis. A quaternary carbon center in the backbone and the accompanying Thorpe-Ingold effect enabled the unprecedented insertion of sp(3) and sp(2) CH bonds that for the first time were incorporated within the backbone of the diyne system and allowed the construction of complex polycyclic carbon scaffolds inaccessible by previous approaches in which the CH bonds for the insertion were situated at the other end of the alkyne.

Unprecedented Formation of the First Alkaline‐Earth‐Metal Complex Bearing an Asymmetrical gem‐Dithiolato Heteroscorpionato Ligand

AbstractThe reaction of the lithium dithioacetate derivative [Li(bdmpzdta)(THF)] [bdmpzdta = bis(3,5‐dimethylpyrazol‐1‐yl)dithioacetate] with 1 equiv. of C3H5MgCl proceeds in high yield to give the first alkaline‐earth‐metal complex bearing an asymmetrical gem‐dithiolato moiety, namely, [Mg(κ3‐NNS‐μ‐S‐bppbte)]3 (1) [bppbte = 1,1‐bis(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)pent‐4‐ene‐2,2‐bis(thiolate)]. This is achieved through an unprecedented insertion reaction of the allyl group into the C=S bond. In contrast, the reaction with the Grignard reagents MeMgCl or EtMgCl leads to the formation of the six‐coordinate sandwich species [Mg(κ3‐bdmpzdta)2] (2), as a result of a rapid ligand redistribution. The molecular structures of 1 and 2 in the solid state have been unambiguously established by single‐crystal X‐ray diffraction studies, which reveal a trinuclear entity with a twisted six‐membered core for 1, in which all magnesium centers are arranged in a distorted trigonal bipyramidal geometry, whereas in 2 the magnesium center has an octahedral coordination environment with two heteroscorpionato ligands, which bind in a κ3‐NNS fashion with a relative trans disposition.

Unusual outcome of the thermolytic condensation of diazoarylmethanes with a [tricarbonyl(η6-2-p-tolyl)chromium]2-oxazolyl chelate of tetracarbonylrhenium

A new Cr(CO)3-bound cyclorhenated 2-phenyl,2-oxazoline derivative was synthesized and treated with two different phenyldiazomethanes, namely Ph2CN2 and (t-Bu)(Ph)N2 under thermolytic conditions in apolar solvents. With the former diazomethane the reaction affords mainly a new bimetallic electron-saturated species resulting from the insertion of the Ph2C moiety into the CAr–Re bond of the rhenacyclic substrate. With the latter diazomethane substituted with one t-butyl group, the reaction quite unexpectedly leads to a new Re(CO)4 metallacycle in which an ortho position is occupied by a (Ph)(t-Bu)(H)C-group, as a possible consequence of an unprecedented insertion–transposition of the Re-centred moiety by C–H bond activation. The results are supported by 6 X-ray structures and analytical informations.

The Fading Right to Property in India

The history of India and its Constitution is writ in superlatives. From the longest text to the largest democracy, the six decades since India became a republic have been eventful ones. In 2011, it has the world's greatest backlog of pending cases1, and a Supreme Court so strident and contradictory that reducing that dubious statistic will be no easy task. For a 2 nation that ranks very low on virtually every single human development index , the access to the most basic rights becomes an insurmountable task. The right to food, shelter and clothing were read into the provision that recognizes the right to life of every individual (Article 21), but even that was some time coming.3 In express terms at the inception, accommodation was made in the Constitution for certain so-called Tundamental Rights', broadly covering four segments individual equality, individual liberty, individual civil rights, and community right to faith and education.4 A violation of any of these rights could be agitated directly in the Supreme Court courtesy Article 32 of the Constitution which guaranteed such a protection. The unprecedented insertion of a provision (Article 13) that permitted the courts to declare a duly enacted law void on the ground that it breached any one or other of the Fundamental Rights was the first sure step in the direction of true judi-

Stereoselective Construction of Seven-Membered Rings with an All-Carbon Quaternary Center by Direct Tiffeneau−Demjanov-type Ring Expansion

Insertion of one methylene unit into the C-C bond of cyclohexanones is a potentially useful, straightforward method for the construction of seven-membered carbocycles. An especially appealing but largely unexplored method in this arena is the nucleophilic addition of diazoalkanes to the Lewis acid-activated cyclohexanones and subsequent ring expansion accompanied by the extrusion of nitrogen (direct Tiffeneau-Demjanov-type ring expansion). Our primary finding is the unprecedented insertion of alpha-alkyldiazoacetates to cyclohexanone and its heteroanalogues, generating seven-membered rings with one all-carbon quaternary center. On the basis of this finding, highly diastereoselective ring expansion of substituted cyclohexanones was developed, furnishing seven-membered rings with 1,4-quaternary-tertiary, 1,4-quaternary-quaternary, or 1,3,5-quaternary-tertiary-tertiary stereogenic centers in a single operation starting from readily available materials. The stereochemical outcome of the product can be easily predicted from the conformation of starting cyclohexanones. Enantioenriched products could be also accessed by the use of (-)-phenylmenthyl alpha-alkyldiazoacetates.

A Germanium(II) Hydride as an Effective Reagent for Hydrogermylation Reactions

Herein we report on the reactivity of the stable germanium(II) hydride LGeH (L = CH{(CMe)(2,6-iPr(2)C(6)H(3)N)}(2)) (2), which contains a low-valent germanium atom. 2 is prepared from the corresponding germanium(II) chloride LGeCl (1) using H(3)Al x NMe(3) or K[HB(iBu)(3)] in toluene. The reaction of 2 with carbon dioxide in toluene at room temperature affords a germanium(II) ester of formic acid, LGe-O-C(O)H (3), which is formed by insertion of the carbon dioxide into the germylene hydrogen bond. 2 also reacts with alkynes at room temperature to give the first germanium(II)-substituted alkenes (4, 5, and 6). These two reaction types have in common the fact that the hydrogen and germylene from LGeH are transferred to an unsaturated bond: the carbon-oxygen double bond (C=O) in the former case and the carbon-carbon triple bond (C[triple bond]C) in the latter. Moreover, the reaction of 2 with elemental sulfur in toluene at room temperature leads to the germanium dithiocarboxylic acid analogue LGe(S)SH (7). Compound 7 is formed by the unprecedented insertion of elemental sulfur into the germylene hydrogen bond and oxidative addition of elemental sulfur to the germanium(II) atom. This leads to the formal conversion of the GeH hydride to a SH proton. Compounds 3-7 were investigated by microanalysis, multinuclear NMR spectroscopy, and single-crystal X-ray structural analyses.