Synthesis and redox catalysis of Carbodiphosphorane ligated stannylene.

Heavier group 14 carbene analogues, exhibiting transition-metal-like behavior, display remarkable capability for small molecule activation and coordination chemistry. However, their application in redox catalysis remains elusive. In this paper, we report the synthesis and isolation of a stannylene with carbodiphosphorane ligand.

Synthesis and Reactivity of an Anionic Diazoolefin.

Bent (hetero)allenes such as carbodicarbenes and carbodiphosphoranes can act as neutral C-donor ligands, and diverse applications in coordination chemistry have been reported. N-Heterocyclic diazoolefins are heterocumulenes, which can function in a similar fashion as L-type ligands. Herein, we describe the synthesis and the reactivity of an anionic diazoolefin.

Head-to-Tail Dimerization of N-Heterocyclic Diazoolefins.

The head-to-tail dimerization of N-heterocyclic diazoolefins is described. The products of these formal (3+3) cycloaddition reactions are strongly reducing quinoidal tetrazines. Oxidation of the tetrazines occurs in a stepwise fashion, and we were able to isolate a stable radical cation and diamagnetic dications.

A Mesoionic Diselenolene Anion and the Corresponding Radical Dianion.

Dichalcogenolenes are archetypal redox non-innocent ligands with numerous applications. Herein, a diselenolene ligand with fundamentally different electronic properties is described. A mesoionic diselenolene was prepared by selenation of a C2-protected imidazolium salt.

Vanadium complexes with N-heterocyclic vinylidene ligands.

The preparation and the structural characterization of vanadium complexes with terminal and bridging N-heterocyclic vinylidene ligands is reported. The synthesis of the complexes was enabled by utilization of diazoolefins as ligand precursors. Structural data and theoretical results show that N-heterocyclic vinylidenes can act as 6e donor ligands, leading to strong metal-carbon interactions.

Isolation and characterization of diazoolefins.

Diazoolefins tend to be highly reactive compounds that rapidly lose dinitrogen. So far, most experimental evidence for diazoolefins is indirect, via trapping experiments. Here we show that diazoolefins are observed to form in reactions of N-heterocyclic olefins with nitrous oxide.

Tuning the π-Accepting Properties of Mesoionic Carbenes: A Combined Computational and Experimental Study.

Mesoionic imidazolylidenes are recognized as excellent electron-donating ligands in organometallic and main group chemistry. However, these carbene ligands typically show poor π-accepting properties. A computational analysis of 71 mesoionic imidazolylidenes that bear different aryl or heteroaryl substituents in C2 position was performed.

Multimodal host-guest complexation for efficient and stable perovskite photovoltaics.

Formamidinium lead iodide perovskites are promising light-harvesting materials, yet stabilizing them under operating conditions without compromising optimal optoelectronic properties remains challenging. We report a multimodal host-guest complexation strategy to overcome this challenge using a crown ether, dibenzo-21-crown-7, which acts as a vehicle that assembles at the interface and delivers Cs ions into the interior while modulating the material. This provides a local gradient of doping at the nanoscale that assists in photoinduced charge separation while passivating surface and bulk defects, stabilizing the perovskite phase through a synergistic effect of the host, guest, and host-guest complex.

Three-membered cyclic digermylenes stabilised by an N-heterocyclic carbene.

Treatment of potassium salts of silole dianions with donor stabilised germanium dichlorides gave the anticipated silagermafulvenylidenes RSi = Ge(Do) (RSi = 1-silacyclopentadiendiyl, Do = N-heterocyclic carbene (NHC)) only as transient intermediates in a side reaction. They were detected by NMR spectroscopy and, in one case, the formal dimer, 2,4-disila-1λ,3λ-digermetane, was isolated. The main products of these reactions are sila-bis-λ-germiranes, directly interconnected digermylenes that are part of a three-membered ring.

Triazene-Activated Donor-Acceptor Cyclopropanes: Ring-Opening and (3 + 2) Annulation Reactions.

Donor-acceptor cyclopropanes substituted with 3,3-dialkyltriazenyl groups are described herein. The strong electron-donating character of the triazene renders the cyclopropanes highly reactive, allowing for catalyst-free ring-opening reactions with methanol and tetracyanoethylene under mild conditions. The triazene-substituted cyclopropanes could also be used as substrates in Lewis acid catalyzed (3 + 2) annulations with silyl enol ethers.

SET processes in Lewis acid-base reactions: the tritylation of N-heterocyclic carbenes.

Reactions between N-heterocyclic carbenes (NHCs) and the trityl cation, [PhC], give covalent adducts of type [NHC-CPh] and/or [NHC-CH-CPh]. EPR spectroscopy, UV-Vis analyses, and trapping experiments imply that adduct formation involves carbene radical cations and the trityl radical. The results demonstrate that single electron transfer (SET) processes should be considered for reaction of NHCs with oxidizing Lewis acids.

Trialkylsilyl-Substituted Silole and Germole Dianions as Precursors for Unusual Silicon and Germanium Compounds.

Group 14 element heteroles are the heavier analogues of cyclopentadienes in which a heavier group 14 element atom replaces the sp carbon atom. In particular siloles and, to a somewhat smaller degree, germoles attracted considerable attention since the early 1990s due to their favorable photophysical properties which allowed the construction of OLEDs using group 14 element heteroles as emissive or electron-transport layers. Anions and in particular dianions derived from group 14 element heteroles have been of substantial interest due to the possible occurrence of Hückel aromaticity involving the heavier main group atom.

Potassium Salts of 2,5-Bis(trimethylsilyl)-Germolide: Switching between Aromatic and Non-Aromatic States.

The reduction of a 1-mesityl-2,5-bis-trimethylsilylchlorogermole 8 with KC is reported. While the reaction with one equivalent of KC gave the dimer with a Ge-Ge bond 10, excess of KC (four equivalents) resulted in the formation of the potassium salt of the germole dianion, 11 with reductive cleavage of the Ge-C bond. Careful reduction with two equivalents of KC in THF provided the potassium salt of the planar germolide 5.

A Germacalicene: Synthesis, Structure, and Reactivity.

The synthesis of the germacalicene 7 from the reaction of the dipotassium germole dianion K [6] with 1,2-bis-diisopropylamino-3-chlorocyclopropenyl perchlorate is reported. Based on the crystal structure analysis and the results of DFT calculations, the germacalicene 7 can be viewed as a cyclopropenium germacyclopentadienide ylide that is isoelectronic to α-cationic phosphanes. First reactivity studies revealed its nucleophilic character and resulted in the isolation of the air- and moisture-stable carbonyl iron complex 15 and the cationic silver complex 20.

Evidence for a Single Electron Shift in a Lewis Acid-Base Reaction.

The Lewis acid-base reaction between a nucleophilic hafnocene-based germylene and tris-pentafluorophenylborane (B(CF)) to give the conventional B-Ge bonded species in almost quantitative yield is reported. This reaction is surprisingly slow, and during its course, radical intermediates are detected by EPR and UV-vis spectroscopy. This suggests that the reaction is initiated by a single electron-transfer step.

A Neutral η -Aminoborole Complex of Germanium(II).

The synthesis of two η -aminoborole complexes of germanium(II) from the reaction of a germole dianion with aminoboron dichlorides is reported. This reaction constitutes a remarkable example of a germole-to-borole transformation. The two aminoborole complexes of germanium(II) were fully characterized by multinuclear NMR spectroscopy, IR spectroscopy, HRMS, and, in one case, by X-ray crystallography.

A Dimeric η ,η -Germole Dianion Bridged Titanium(III) Complex with a Multicenter Ti-Ge-Ge-Ti Bond.

Dimeric germole dianion bridged Ti and Zr complexes have been synthesized. In these complexes, the germole dianion adopts a formal η ,η coordination to the two metal centers. The bonding situation in these bridged dimers is dominated by a covalent Ge-Ge interaction that results, for example, in a strong antiferromagnetic coupling of the d Ti centers.

Hafnocene-based Bicyclo[2.1.1]hexene Germylenes - Formation, Reactivity, and Structural Flexibility.

2,5-Disilylsubstituted germole dianions 1 react with hafnocene dichloride to give hafnocene-based bicyclo[2.1.1]hexene germylenes 3.

A One-Step Germole to Silole Transformation and a Stable Isomer of a Disilabenzene.

An unusual germole-to-silole transformation is described. As key intermediates hetero-fulvenes are formed which rearrange to more stable bicyclic carbene analogues. The so-formed germylenes undergo a reductive elimination yielding elemental germanium and siloles.

A Stable Silylene with a σ, π- Butadiene Ligand.

The synthesis of a new type of silylene 1 is reported. It adopts a bicyclo[2.1.

Dihydrogen Splitting Using Dialkylsilylene-Based Frustrated Lewis Pairs.

Isolable dialkylsilylene 5 reacts with dihydrogen in the presence of a small amount of a conventional Lewis acid (BPh , BEt ) or a base (PPh , PEt , NPh , NEt ) at low temperatures in a hydrocarbon solvent, giving the corresponding dihydrosilane 10 in high yields. Both 5/Lewis acid and Lewis base/5 pairs work as a frustrated Lewis pair (FLP) to split dihydrogen, being in accord with the amphoteric nature of silylene 5.

A Germylene Stabilized by Homoconjugation.

The synthesis of a bicyclic germylene from the reaction of a germole dianion with hafnocene dichloride is reported. This germylene is stabilized by a homoconjugative interaction of the dicoordinated germanium atom with a remote C=C double bond. First reactivity studies revealed its nucleophilic character and resulted in the synthesis of bimetallic hafnium/iron and hafnium/tungsten complexes with a germylene group linker.

1,3-Diazasilabicyclo[1.1.0]butane with a Long Bridging N-N Bond.

A 1,3-diazasilabicyclo[1.1.0]butane (1) is synthesized as thermally stable crystals by using the cycloaddition reaction of an isolable dialkylsilylene with aziadamantane.

Elusive 2H-1,2-oxasiletes through reactions of an isolable dialkylsilylene with diazocarbonyl compounds.

The reactions of isolable dialkysilylene 1 with 2-diazo-1,2-diphenylethanone and ethyl 2-diazo-2-phenylacetate gave elusive silacycles, 2H-1,2-oxasiletes 2 and 3, respectively, in high yields. Because these reactions occur at low temperatures of ca.-30 °C, initial complexation of the silylene to the carbonyl oxygen of the diazocarbonyl compounds is suggested to trigger dinitrogen elimination followed by cyclization.

[XbaI polymorphisms of the estrogen receptor gene and bone mineral density and BMI in Beijing Han women].

The work is to study the relationship between XbaI polymorphisms of the estrogen receptor (ER) gene and bone mineral density in Beijing Han women. Bone mineral density(BMD) was measured at lumbar spine,proximal femoral and arm by dual energy X-ray absorptiometry(DEXA) and ER gene was determined by polymerase Chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 179 Beijing Han women. The frequency of the ER genotype of XX, Xx and xx was 0.