Me2Se and Me2Te: their structures and synergistic effects of halogen/chalcogen bonding with C6F5Br and C6F5I.

This work combines halogen and chalcogen bonding. Short, polarity directed C-X⋅⋅⋅Ch (X = Br or I, Ch = Se or Te) contacts were prepared by in situ low-temperature cocrystallization of liquid mixtures of neutral pentafluorohalogenobenzenes C6F5X and dimethyl chalco-genides Me2Ch. Solid-state structures of Me2Se and Me2Te were determined 150 and 125 years after their first description.

Annulated carbocyclic gallylene and bis-gallylene with two-coordinated Ga(i) atoms.

The first carbocyclic gallylene [(ADC)Ga(GaI)] and bis-gallylene [(ADC)Ga] (ADC = PhC{N(Dipp)C}; Dipp = 2,6-iPrCH) featuring a central CGa ring annulated between two 1,3-imidazole rings are prepared by KC reductions of [(ADC)GaI]. Treatment of [(ADC)Ga] with Fe(CO) affords complex [(ADC)GaFe(CO)] in which each Ga(i) atom serves as a two-electron donor. [(ADC)Ga] activates white phosphorus (P) and the C -F bond of aryl fluorides (ArF) to yield compounds [(ADC)Ga(P)] and -/-[(ADC)GaF(Ar)], respectively.

Fluoromethyl Triflate and Fluoromethyl Fluorosulfonate: Easily Accessible and Powerful Fluoromethylation Reagents.

Fluoromethyl triflate (superfluoromethyl, SFM, FHCOSOCF) and fluoromethyl fluorosulfonate (magic fluoromethyl, MFM, FHCOSOF) are two easily synthesized, highly effective and non-ozone depleting fluoromethylation reagents. They are analogous to the well-known and widely used methylation reagents HCOSOCF and HCOSOF. Both SFM and MFM have been fully characterized by multinuclear NMR spectroscopy (H, C, O, F, S).

Annulated 1,4-Disilabenzene-1,4-diide and Dihydrogen Splitting.

The isolation of silicon analogues of phenyl anions such as (CH) and (CH) is challenging owing to their extremely high reactivity associated with their silylene character and weak C-Si π-interaction. Herein, we report the first annulated 1,4-disilabenzene-1,4-diide compound [(ADC)Si] () based on anionic dicarbene (ADC) scaffolds (ADC = PhC{N(Dipp)C}; Dipp = 2,6-PrCH) as a green-yellow crystalline solid. Compound is prepared by KC reduction of the Si(IV) chloride [(ADC)SiCl] () or the cyclic bis-chlorosilylene [(ADC)SiCl] (), which are also prepared for the first time.

Highly Cytotoxic Cryptophycin Derivatives with Modification in Unit D for Conjugation.

Cytotoxic payloads for drug conjugates suitable for directed tumor therapy need to be highly potent and require a functional group for conjugation with the homing device (antibody, peptide, or small molecule). Cryptophycins are cyclodepsipeptides that stand out from the realm of natural products due to their extraordinarily high cytotoxicity. However, the installation of a suitable conjugation handle without compromising the toxicity is highly challenging.

Halogen Bonding in N-Alkyl-Bromo-/Lodo-Pyridinium Salts and its Application in Chromatography.

The alkylation of 3-/4-bromo- and -iodopyridine with methyl triflate smoothly affords the corresponding N-methylpyridinium triflate salts. An anion exchange with NaI or [PPh]Y (Y=Cl, Br, I) yields the corresponding halide salts. Most of them could be structurally characterized and their strong halogen bonds were investigated.

Adducts of Lewis acidic stibanes with phosphane chalcogenides.

Starting from ClSbR (R = CF, 3,5-(CF)CH) and H(E)P(Bu) (E = O, S), we prepared the oxy- and sulphanediyl-bridged adducts RSb(Cl)-E-(H)P(Bu), which are stable against the elimination of HCl. The different electron-withdrawing substituents and chalcogen bridging units influence the size of the Sb-E-P angle. ClSb(CF) and BuSnH react to give HSb(CF), which seems to interact weakly with H(O)P(Bu) in solution as observed NMR.

Chemical constituents of Schott leaves and their cytotoxic activities.

Chromatographic fractionation of CHCl:MeOH (1:1) extract of Schott cultivated in Egypt afforded four compounds, lupeol acetate (), -13--manoyl oxide (), 5-methoxymethyl-7,8-dimethyltocol (), and -tocopherol quinone (). The planar structures of the isolated compounds were concluded based on HRESIMS and NMR spectroscopy. X-ray crystallography of is reported herein for the first time and its unambiguous absolute configuration was deduced from anomalous dispersion.

Chlorodefluorination Induced by Gallium-Based Lewis Acids.

The reaction of [Ga(CF)(FSiMe)] with chlorotrimethylsilane leads to the selective substitution of the α-fluorine atoms by chlorine atoms and thus to the formation of [Ga(CClCF)(FSiMe)]. The corresponding chlorogallate ion, [Ga(CClCF)Cl], could be isolated and structurally characterized as its tetraphenylphosphonium salt. The catalytic potential of [Ga(CClCF)(FSiMe)] was demonstrated via the chlorodefluorination of MeSiCF, 2,2-difluoropropane and [PPh][Ga(CF)].

Non-Kekulé meta-Quinodimethane Singlet Diradicals Based on Classical N-Heterocyclic Carbenes.

Diradicals based on a meta-quinodimethane (m-QDM) scaffold generally have a triplet ground state and are rather scarce. Herein, m-QDM-based non-Kekulé diradicals [3,3'-(NHC)BP] (3-NHC) (NHC = SIPr = C{N(Dipp)CH}; IPr = C{N(Dipp)CH}, Me-IPr = C{N(Dipp)CMe}; Dipp = 2,6-iPrCH; BP = 1,1'-CHCH) featuring N-heterocyclic carbene (NHC) pendants are reported as crystalline solids. The EPR spectra of 3-NHC show both allowed (Δm = 1) and forbidden (Δm = 2; 'half-field') transitions characteristic for triplet diradicals.

A geminal antimony(iii)/phosphorus(iii) frustrated Lewis pair.

The geminal Lewis pair (FC)SbCHP(Bu) (1) was prepared by reacting (FC)SbCl with LiCHP(Bu). Despite its extremely electronegative pentafluoroethyl substituents, the neutral 1 exhibits a relatively soft acidic antimony function according to the HSAB concept (hard-soft acid-base). These properties lead to a reversibility in the binding of CS to 1, as observed by VT-NMR spectroscopy, while no reaction with CO is observed.

First Main-Group Element Lewis Acid Thionyl Chloride Adduct and its Chemistry.

Although the adduct of aluminum trichloride with thionyl chloride has been reported, no thionyl chloride adduct of a main group element Lewis acid or organometallic compound has been structurally characterized. In this communication we present the synthesis and reactivity of the structurally ascertained adduct of thionyl chloride with tris(pentafluoroethyl)gallane as a representative of a main group element Lewis acid. Gallium and indium compounds with electron withdrawing groups, e.

Polydentate chalcogen bonding: anion trapping with a water-stable host compound carrying Se-CF functions.

Bidentate and tetradentate chalcogen bonding host systems with SeCF functions as σ-hole donors in close proximity at the alkyne functions of 1,8-diethynylanthracene and its -dimer were prepared in quantitative yield by tin-selenium exchange reactions of the corresponding trimethylstannyl precursors with ClSeCF. The bidentate system shows chalcogen bonding interactions with THF, but does not bind halide ions. The tetradentate system cooperatively chelates chloride, bromide and iodide ions with its four CC-SeCF units by rotating the four σ-holes towards the halide ion.

Host-guest chemistry of tridentate Lewis acids based on tribenzotriquinacene.

Flexible poly-Lewis acids (PLA) based on the tribenzotriquinacene (TBTQ) scaffold have been synthesised. Hydrosilylation of 4b,8b,12b-triallyltribenzotriquinacene and subsequent exchange of the chlorine substituents with weaker coordinating triflate groups afforded a novel triple silyl-functionalised PLA. By regioselective hydroboration of triallyl-TBTQ with various organoboranes, PLAs with different Lewis acidities were obtained.

Oxidation-dependent Lewis acidity in chalcogen adducts of Sb/P frustrated Lewis pairs.

The reactions of the frustrated Lewis pair (FC)SbCHP(Bu) with oxygen, sulphur, selenium and tellurium led to the mono-oxidation products (FC)SbCHP(E)(Bu) (E = O, S, Se, Te). Further oxidation of these chalcogen adducts with tetrachloro--benzoquinone (-chloranil) gave (FC)Sb(CH)(μ-E)P(Bu)·Cat (Cat = -OCCl) with a central four-membered ring heterocycle for E = O, S, and Se. For E = Te the elimination of elemental tellurium led to an oxidation product with two equivalents of -chloranil, (FC)SbCHP(Bu)·2Cat, which is also accessible by reaction of (FC)SbCHP(Bu) with -chloranil.

Tridentate Lewis Acids Based on Tribenzotriquinacene Chalices.

Chalice-shaped tridentate poly-Lewis acids (PLA) based on the tribenzotriquinacene (TBTQ) scaffold have been synthesised. Stannylation of the alkyne units, attached via phenyl-spacers to the benzhydrylic positions to the TBTQ scaffold, with MeNSnMe afforded the trimethyltin substituted TBTQ derivative. Replacement of these tin functions with other elements resulted in rigid boron- and aluminium-functionalised PLAs.

Bidentate boron Lewis acids: synthesis by tin boron exchange reaction and host-guest complex formation.

Four bidentate boron Lewis acids based on the 1,8-diethynylanthracene backbone have been synthesized by a tin-boron exchange reaction with various chloroboranes, yielding the products in good to excellent yields. Complexation experiments of the host compounds with pyridine, pyrimidine and TMEDA demonstrated striking differences in terms of formation and solubility of the supramolecular adducts. The host-guest complexes were investigated by multinuclear NMR spectroscopy and structurally characterized by X-ray diffraction experiments, illustrating the adaptation of the host system upon adduct formation with different neutral guest molecules.

Structure and photochemistry of di--butyldiphosphatetrahedrane.

Di--butyldiphosphatetrahedrane (BuCP) (1) is a mixed carbon- and phosphorus-based tetrahedral molecule, isolobal to white phosphorus (P). However, despite the fundamental significance and well-explored reactivity of the latter molecule, the precise structure of the free (BuCP) molecule (1) and a detailed analysis of its electronic properties have remained elusive. Here, single-crystal X-ray structure determination of 1 at low temperature confirms the tetrahedral structure.

Hexadentate poly-Lewis acids based on the bowl-shaped tribenzotriquinacene.

Hexadentate poly-Lewis acids (PLA) based on the bowl-shaped tribenzotriquinacene (TBTQ) have been synthesised. The introduction of three -propyl groups into the benzhydrylic positions of the TBTQ backbone has significantly increased the solubility of the subsequently derived compounds. Semi-flexible PLAs containing boron and aluminium were obtained by hydrometallation of the corresponding 2,3,6,7,10,11-hexaalkynyl-TBTQ.

N-Heterocyclic Carbene Analogues of Wittig Hydrocarbon.

N-Heterocyclic carbene (NHC) analogues of Wittig hydrocarbon, [(NHC)(Stil)(NHC)] (3a-c) (NHC = SIPr (1a) = C[N(Dipp)CH], Dipp = 2,6-iPrCH; IPr (1b) = C[N(Dipp)CH]; Me-IPr (1c) = C[N(Dipp)CMe] and Stil = CHCHCHCH) have been reported as crystalline solids. 3a-c are prepared by two-electron reductions of the corresponding bis-1,3-imidazoli(ni)um bromides [(NHC)(Stil)NHC)](Br) (2a-c) with KC in >94 % yields. 2a-c are accessible by the nickel catalyzed direct C-C coupling of NHCs (1a-c) with (E)-4,4'-dibromostilbene.

Selectivity in Adduct Formation of a Bidentate Boron Lewis Acid.

A bidentate boron Lewis acid based on 1,8-diethynylanthracene has been studied in detail with respect to its adduct formation with diamines and diphosphanes of different linker lengths between the donor functions. A clear correlation between the linker length of the bifunctional base and the formation of 1 : 1 adducts, 1 : 2 adducts or oligomers was found. The adducts were characterized in solution by NMR titration experiments and structurally by X-ray diffraction.

Access to a peri-Annulated Aluminium Compound via C-H Bond Activation by a Cyclic Bis-Aluminylene.

Carbocyclic aluminium halides [(ADC)AlX] (2-X) (X=F, Cl, and I) based on an anionic dicarbene (ADC=PhC{N(Dipp)C}, Dipp = 2,6-iPrCH) framework are prepared as crystalline solids by dehydrohalogenations of the alane [(ADC)AlH] (1). KC reduction of 2-I affords the peri-annulated Al(III) compound [(ADC)AlH] (4) (ADCPhC{N(Dipp)C(Dipp)N}, Dipp=2-iPr,6-(MeC)CH)) as a colorless crystalline solid in 76 % yield. The formation of 4 suggests intramolecular insertion of the putative bis-aluminylene species [(ADC)Al] (3) into the methine C-H bond of HCMe group.

Divergent Reactivity of a Cyclic Bis-Hydridostannylene: A Masked Sn(I) Diradicaloid.

Herein, reactivity studies of a cyclic bis-hydridostannylene [(ADC)SnH] (1-H) (ADC=PhC{(NDipp)C}; Dipp=2,6-iPrCH) with various unsaturated organic substrates are reported. Reactions of terminal alkynes (RC≡CH) with 1-H afford mixed acetylide-vinyl-functionalized bis-stannylenes via dehydrogenation and hydrostannylation. Treatment of 1-H with PhC≡CCH gives a unique distannabarrelene via dehydrogenative C-H stannylation and hydrostannylation of the C≡CCH moiety.

Boosting the π-Acceptor Property of Mesoionic Carbenes by Carbonylation with Carbon Monoxide.

We report the room temperature dimerization of carbon monoxide mediated by C4/C5-vicinal anionic dicarbenes Li(ADC) (ADC = ArC{(Dipp)NC} ; Dipp = 2,6-iPr C H ; Ar = Ph, DMP (4-Me NC H ), Bp (4-PhC H )) to yield (E)-ethene-1,2-bis(olate) (i.e. O-C=C-O = CO ) bridged mesoionic carbene (iMIC) lithium compounds CO -[(iMIC)Li] (CO -[iMIC] = [ArC{(Dipp)NC} (CO)] ) in quantitative yields.