Tetra-Cationic Distibane Stabilized by Bis(α-iminopyridine) and Its Reactivity.

The work establishes the salt of a tetra-cationic distibane, [LSb][CFSO] = [][OTf] (CFSO = OTf), stabilized by a bis(α-iminopyridine) ligand , defying the Coulombic repulsion. The synthetic approach involved a dehydrocoupling reaction when a mixture of and Sb(OTf) in a 1:1 ratio was treated with EtSiH/LiBEtH as the hydride source. Compound [][OTf] was also achieved from [LSbCl][OTf] as a precursor and using EtSiH.

Reactivity Study of the Bis(phosphine)-Stabilized Antimony(I) Cation.

The 5,6-Bis(diisopropylphosphino)acenaphthene -stabilized Sb(I) cationic compound [LSb][OTf] (OTf = CFSO) possessing two lone pairs of electrons on the Sb(I) center showed nucleophilic behavior toward methyl trifluoromethanesulfonate forming the oxidized product [LSbMe][OTf] (OTf = CFSO). Reaction of compound with Lewis acids such as GaCl and AlBr led to changes in the counteranions only giving products [LSb][GaCl] and [LSb][SbBr] , respectively. A metathesis reaction was observed when compound was reacted with PI.

Dianionic and Neutral Diboron-Centered Classical Diradicaloids.

Herein, we report the syntheses and electronic structures of crystalline dianionic as well as neutral diboron-centered classical diradicaloids as boron analogues of classical Thiele, Chichibabin, and Müller (this only for dianionic diradicaloids!) hydrocarbons. These are based on borane radical anion and NHC-stabilized boryl radical spin carriers, respectively. All these dianionic diboron-centered diradicaloids exhibit triplet population at room temperature regardless of the π-conjugated spacer: -phenylene, ,-biphenylene, or ,-terphenylene.

Intramolecular donor-stabilized tetra-coordinated germanium(iv) di-cations and their Lewis acidic properties.

We report the first examples of intramolecular phosphine-stabilized tetra-coordinated germanium(iv) di-cationic compounds: [LGe][CFSO]3 and [LGe][CFSO]3 (L = 6-(diisopropylphosphanyl)-1,2-dihydroacenaphthylene-5-ide; L = 6-(diphenylphosphanyl)-1,2-dihydroacenaphthylene-5-ide). The step wise synthetic strategy involves the isolation of neutral and mono-cationic Ge(iv) precursors: [LGeCl][X] (X = GeCl1, OTf 2), [LGeCl] 1 and [LGeCl][OTf] 2. Both 3 and 3 exhibit constrained spiro-geometry.

Comment on "Disclosing Cyclic(Alkyl)(Amino)Carbenes as a One-Electron Reductant: Synthesis of Acyclic(Amino)(Aryl)Carbene-Based Kekulé Diradicaloids".

This correspondence addresses a misassignment of an EPR spectrum of 2 in a recent publication (Chem. Eur. J.

Coordination Chemistry of the Antimony(III) and Bismuth(III) Cations using Bis(α-iminopyridine) as Ligand.

Bis(alpha-iminopyridine) L has been employed as the redox non-innocent Schiff-base ligand to coordinate with cationic antimony(III) and bismuth(III) centers. Mono- and di- cationic compounds: [LSbCl ][CF SO ] 1, [LBiCl ][CF SO ] 2, [LSbCl ] [Sb Cl ] 3, [LBiCl ] [Bi Cl ] 4, [LSbCl][CF SO ] 5, [LBiCl][CF SO ] 6 have been isolated and characterized using single crystal X-ray crystallography in the solid-state and solution-state NMR studies. These compounds have been prepared from PnCl (Pn=Sb, Bi) and chloride abstracting agent such as Me SiCF SO or AgCF SO in the presence of L.

Reduction of 2--substituted pyrrolinium cations: the carbon-carbon single bond in air stable 2,2'-bipyrrolidines as a two-electron-source.

Reduction of 2--substituted pyrrolinium cations initially formed secondary radicals results in either dimerisation or -abstracted products, while the outcome depends on the -substituents. The resultant central carbon-carbon single bond in the dimerised 2,2'-bipyrrolidine derivatives can be oxidised chemically and electrochemically. The notably air and moisture-stable dimers were subsequently utilised as a source of two electrons in various chemical transformations.

Reply to the 'Comment on "The oxidation state in low-valent beryllium and magnesium compounds"' by S. Pan and G. Frenking, , 2022, , DOI: 10.1039/D2SC04231B.

A recent article by Pan and Frenking challenges our assignment of the oxidation state of low valent group 2 compounds. With this reply, we show that our assignment of Be(+2) and Mg(+2) oxidation states in Be(cAAC) and Mg(cAAC) is fully consistent with our data. Some of the arguments exposed by Pan and Frenking were based on visual inspection of our figures, rather than a thorough numerical analysis.

Air and Moisture Stable - and -Quinodimethane Derivatives Derived from --Heterocyclic Olefins.

Herein we report the development of a new methodology for the synthesis of various quinodimethane derivatives under two-electron oxidation of --heterocyclic olefins linked by different π-conjugated aromatic spacers. In case of - and -phenylene bridge, we obtained air and moisture stable diimidazolium - and -quinodimethane derivatives. Analogues of the -phenylene spacer such as tetrafluoro--phenylene and -anthracene also led to the corresponding air and moisture stable quinodimethane derivatives.

Carbodicarbenes and Striking Redox Transitions of their Conjugate Acids: Influence of NHC versus CAAC as Donor Substituents.

Herein, a new type of carbodicarbene (CDC) comprising two different classes of carbenes is reported; NHC and CAAC as donor substituents and compare the molecular structure and coordination to Au(I)Cl to those of NHC-only and CAAC-only analogues. The conjugate acids of these three CDCs exhibit notable redox properties. Their reactions with [NO][SbF ] were investigated.

The oxidation state in low-valent beryllium and magnesium compounds.

Low-valent group 2 (E = Be and Mg) stabilized compounds have been long synthetically pursued. Here we discuss the electronic structure of a series of Lewis base-stabilized Be and Mg compounds. Despite the accepted zero(0) oxidation state nature of the group 2 elements of some recent experimentally accomplished species, the analysis of multireference wavefunctions provides compelling evidence for a strong diradical character with an oxidation state of +2.

Realizing 1,1-Dehydration of Secondary Alcohols to Carbenes: Pyrrolidin-2-ols as a Source of Cyclic (Alkyl)(Amino)Carbenes.

Herein we report secondary pyrrolidin-2-ols as a source of cyclic (alkyl)(amino)carbenes (CAAC) for the synthesis of CAAC-Cu -complexes and cyclic thiones when reacted with Cu -salts and elemental sulfur, respectively, under reductive elimination of water from the carbon(IV)-center. This result demonstrates a convenient and facile access to CAAC-based Cu -salts, which are well known catalysts for different organic transformations. It further establishes secondary alcohols to be a viable source of carbenes-realizing after 185 years Dumas' dream who tried to prepare the parent carbene (CH ) by 1,1-dehydration of methanol.

Disclosing Cyclic(Alkyl)(Amino)Carbenes as One-Electron Reductants: Synthesis of Acyclic(Amino)(Aryl)Carbene-Based Kekulé Diradicaloids.

Herein, we disclose cyclic(alkyl)(amino)carbenes (CAACs) to be one-electron reductants under the formation of a transient radical cation as indicated by EPR spectroscopy. The disclosed CAAC reducing reactivity was used to synthesize acyclic(amino)(aryl)carbene-based Thiele and Chichibabin hydrocarbons, a new class of Kekulé diradicaloids. The results demonstrate CAACs to be potent organic reductants.

Stabilization of the Elusive Antimony(I) Cation and Its Coordination Complexes with Transition Metals.

Upon stabilization by 5,6-bis(diisopropylphosphino)acenaphthene to form compound 1, the fugitive antimony (I) cation exhibited nucleophilic behavior towards coinage metals. Compound 1 was strategically synthesized at room temperature from SbCl , the bis(phosphine), and trimethylsilyl trifluoromethanesulfonate taken in a 1:2:3 ratio, whereby the bis(phosphine) plays the dual role of a reductant and a supporting ligand. The generation of 1 involves two-electron oxidation of the ligand to form a P-P bonded diphosphonium dication.

α,α'-Diamino--tetrafluoroquinodimethane: Stability of One- and Two-Electron Oxidized Species and Fixation of Molecular Oxygen.

Herein, we report the synthesis, characterization, and reactivity of α,α'-diamino--tetrafluoroquinodimethane, a -tetrafluorophenylene-bridged monosubstituted carbene-based Thiele's hydrocarbon . The compound exhibits a reversible two-step one-electron oxidation with a marginally stable radical cation state . The formation of the radical cation could be confirmed by electron paramagnetic resonance spectroscopy.

Reactivity of NHC/diphosphene-coordinated Au(I)-hydride.

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.

α,α'-Diamino--quinodimethanes with Three Stable Oxidation States.

Herein, we report the rational design, synthesis, and characterization of α,α'-diamino-substituted--quinodimethanes, which are a group of partially substituted -quinodimethanes. These exhibit two reversible one-electron redox steps and electrochromism in the ultraviolet, visible, and near-infrared regions. We were able to isolate the crystalline compounds of all three oxidation states: neutral, radical cation, and dication.

Equilibrium Formation of Stable All-Silicon Versions of 1,3-Cyclobutanediyl.

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 Tip (Tip=2,4,6-triisopropylphenyl) with the N-heterocyclic silylenes c-[(CR CH )(NtBu) ]Si: (R=H or methyl) with saturated backbones.

Contrasting reactivity of (boryl)(aryl)lithium-amide with electrophiles: N- vs. p-aryl-C-nucleophilic substitution.

Herein we report two different reactivity modes of lithium(aryl)(boryl)amide, 4, when it is reacted with chlorosilanes such as SiCl4 and MeSiHCl2, and chlorophosphine, Ph2PCl. Thus, the reaction of lithium(aryl)(boryl)amide, 4, with MeSiHCl2 leads exclusively to an N-substitution product, 6. On the other hand, the reaction of 4 with SiCl4 and Ph2PCl proceeds completely differently affording exclusively p-aryl-C-substitution products, 5 and 7, respectively.

Reactivity enhancement of a diphosphene by reversible N-heterocyclic carbene coordination.

Diphosphene TerP = PTer (; Ter = 2,6-MesCH; Mes = 2,4,6-MeCH) and NHC (NHC = 1,3,4,5-tetramethylimidazol-2-ylidene) exist in an equilibrium mixture with the NHC -coordinated diphosphene . While uncoordinated is inert to hydrolysis, the NHC adduct readily undergoes hydrolysis to afford a phosphino-substituted phosphine oxide with the liberation of NHC . On this basis, conditions suitable for the catalytic use of NHC were identified.

Reactivity of silagermenylidene toward nitrous oxide: a preliminary DFT study.

The possible reaction mechanism of silagermenylidene and its NHC (N-heterocyclic carbene) coordinated form with NO were investigated by DFT methods. Mainly, the potential energy surfaces of the five pathways I-IV were explored. Pathways I, II, III, and III' deal with the oxidation of silagermenylidene, whereas that of NHC coordinated form is associated with pathways I, III, III', and IV.

NHC-stabilized 1-hydrosilaimine: synthesis, structure and reactivity.

A facile, straightforward synthesis of N-heterocyclic carbene (NHC)-stabilized 1-hydrosilaimine starting from a silicon(iv)-precursor is reported. It has been employed for the addition of an O-H bond of water under ambient conditions without any additional catalyst.

Assembly of NHC-stabilized 2-hydrophosphasilenes from Si(iv) precursors: a Lewis acid-base complex.

NHC-stabilized 2-hydrophosphasilenes are obtained from 1,2-dihydro-2-chlorophosphasilanes as Si(iv) precursors by a NHC-assisted 1,2-elimination of HCl. The NHC-exchange of these compounds is demonstrated as a proof of donor acceptor bonding between NHC and the silicon centre of the "Si[double bond, length as m-dash]P" moiety. We have also explored the possibility of similar exchanges in NHC-stabilized Si and P compounds.

Regiodiscriminating Reactivity of Isolable NHC-Coordinated Disilenyl Germylene and Its Cyclic Isomer.

An isolable NHC-coordinated disilenyl germylene RSi═SiR-GePh·NHC (5b: R = 2,4,6-triisopropylphenyl, NHC = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) is obtained from the reaction of the α-chloro silyl functionalized heavier vinylidene analogue R(Cl)Si-RSi═Ge·NHC with phenyllithium. The disilenyl germylene 5b isomerizes at 40 °C to the NHC-adduct of the corresponding heavier cyclopropylidene analogue 6b. Both 5b and 6b display near perfect regiodiscrimination in their reactions with phenylacetylene and xylyl isocyanide, affording in the case of each reagent two different regioisomers of NHC-coordinated cyclic germylenes.