Synthesis,structure, and thermal destruction of aroxytetraphenylstiboranes

A series of aroxytetraphenylstiboranes, Ph₄SbOAr, were obtained by the reaction of pentaphenylstiborane with phenols at 20 °C. The thermolysis of these compounds givesO- or o-C-phenylation products. The thermolysis of stiboranes, which incorporate aryl groups containing electron-withdrawing substituents (Ar=2,4-Br₂, 2,4-Cl₂, 2-NO₂, 4-OPh) produces predominantly simple diaryl ethers of asymmetric structure in 58 %, 90 %, 32 %, and 60 % yields, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 958–963, May, 1995.     

A reaction of 3,6-di(tert-butyl)-4-chloro-1,2-benzoquinone with potassium ethyl xanthate. New sulfur-containing o-quinones

In a reaction of 3,6-di(tert-butyl)-4-chloro-1,2-benzoquinone with potassium ethyl xanthate, the halogen atom was replaced by the ethyl xanthate group. Acid hydrolysis of the product gave 4,7-di(tert-butyl)-5,6-dihydroxy-1,3-benzodithiol-2-one containing a pyrocatechol fragment, which was oxidized into the corresponding quinone. When irradiated in solution with visible light, this quinone quantitatively eliminated a CO molecule with contraction of the ring to a five-membered one. The quinones obtained were studied as ligands in coordination spheres of metals by ESR spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 683–686, April, 2006.     

Oxidation of Aromatic Compounds: XIII. Oxidation of Unsymmetrically Substituted 1,3-Diarylpropynones in a System CF<Subscript>3</Subscript>CO<Subscript>2</Subscript>H-CH<Subscript>2</Subscript>Cl<Subscript>2</Subscript>-PbO<Subscript>2</Subscript>

Oxidation of unsymmetrically sunstituted 1,3-diarylpropynones in a system trifluoroacetic acid-dichloromethane-lead(IV) oxide proceeds through intermediate formation of cation radicals and occurs regio- and stereoselectively affording E-1,1,2,2-tetraaroylethenes. The highest yield of these compounds was obtained from 1,3-diarylpropynones containing electron-donor methoxy and methyl groups in the aromatic ring conjugated with the triple bond.     

Reactions of Vinyl Type Carbocations Generated in Fluorosulfonic Acid with Benzene Derivatives. New Synthesis of Alkyl 3,3-Diarylpropenoates

Vinyl type carbocations ArC⁺=CHX [X = CO₂H, CO₂Alk, C≡N, P(O)(OAlk)₂] generated from alkyl 3-arylpropynoates and related compounds in fluorosulfonic acid at ?75 to ?20°C react with various benzene derivatives, following the mechanism of electrophilic substitution of hydrogen. A new procedure for the synthesis of alkyl 3,3-diarylpropenoates having various substituents in the aryl fragments has been developed on the basis of protonation of the triple bond in alkyl 3-arylpropynoates.     

Intramolecular C—F→Ln dative interactions in lanthanide complexes with fluorinated ligands

Complexes reported in the literature and potentially capable of intramolecular C—F→Ln interactions were analyzed. It was proposed to use the ToposPro software for structural and topological analysis to search for intramolecular C—F→Ln interactions. The shortest detected Ln···F contact amounted to 2.374 Å, while the longest weak non-valence contact was 4.060 Å. For all lanthanide complexes with Ln···F distances shorter than 3.447 Å, only strong intramolecular (valence) interactions between these atoms were observed. These interactions can affect the physicochemical properties of complexes and they are to be taken into account in determination of the coordination environment of lanthanide atoms.     

Crystal packing and reactivity of di(meth)acrylates of some derivatives of hydroquinone and pyrocatechol in melts

The X-ray diffraction study of 2,2′-(1,2-phenylene-bis(oxy)diethanol and 2,2′-(1,4-phenylenebis(oxy)diethanol dimethacrylates and 2,2′-(1,4-phenylenebis(oxy)diethanol diacrylate (T _m = 40–42, 68–70, and 62–64°C, respectively) indicates that oligomer molecules are packed in crystals as stacks in which methacrylate fragments of adjacent molecules are parallel to each other. The minimum distances between the centers of C=C double bonds of adjacent methacrylate fragments in crystals of di(meth)acrylates are 4.373, 4.215, and 3.996 respectively. The conversion dependences of the reduced rates of photopolymerization of melted oligomers (9,10-phenanthrenequinone as a photoinitiator) pass through maxima at conversions of 40, 11, and 2%, while the ultimate conversions are 85, 33, and 73%, respectively. The addition of ionic liquids based on phosphonium and imidazolium cations to dimethacrylates of 2,2′-(1,2-phenylenebis(oxy)diethanol and triethylene glycol increases the maximum reduced rate of photopolymerization.     

1,3-Bis(alkylimino)isoindolinates of rare earth metals: Synthesis,molecular structure and photoluminescence

The rare earth metal isoindolinates Ln(ⁱPrL)₃ (Ln = Sc (1), Y (2), Eu (3), Dy (4), Yb (5); ⁱPrL = 1,3-bis(isopropylimino)isoindolinate anion) and [(MeL)Ce]₂(μ-MeL)₄ (6) (MeL = 1,3-bis(methylimino)isoindolinate anion) were synthesized by reactions of the amides Ln[N(SiMe₃)₂]₃ with 1,3-bis(isopropylimino)isoindoline (ⁱPrLH) or 1,3-bis(methylimino)isoindoline (MeLH), respectively. The X-ray diffraction study revealed that in monomeric molecules of the isopropyl-substituted compounds 2 and 4 the cations Ln³⁺ are η²-coordinated by three isoindolinate ligands. The methyl-substituted 6 exists in a crystal as a dimer containing two terminal η²-coordinated ligands and four bridging isoindolinate ligands two of which are bonded to Ce atoms in η³ fashion (η:η:η-N,N,N) but two others in η⁴ manner (η:η²:η-N,N,N). All the obtained complexes in solutions exhibited ligand-centered photoluminescence, the spectra of which consist of one broadened band with a maximum at 400–450 nm.     

Analysis of the supramolecular structures of Sb(III) and Sb(V) catecholate complexes from the viewpoint of ligand solid angles

The ligand solid angle approach has been successfully applied to the analysis of the catecholate complexes of Sb(III) and Sb(V). The Sb(III) complexes possess an electron lone pair that influences their molecular structure but does not behave as a classic “ligand” when intermolecular interactions are concerned. The Sb(III) complexes in solid state form numerous intermolecular interactions that effectively increase metal shielding, and herein we analyze the effects of the lone pair of electrons on the complex coordination geometry. In the five-coordinate R₃CatSb(V) complexes (Cat = catecholate ligand, R = Ph, Me, Cl) the metal is shielded by 87(3)% and multiple intermolecular contacts are observed. The central metal in the six-coordinate antimony(V) complexes R₃CatSb(V) · L is shielded to the extent of 89(2)% and no strong attractive intermolecular interactions are detected in solid state. Thus, the metal shielding in excess of 85% is required to prevent complex dimerization or additional ligation of the central atom by a nucleophile.     

New yttrium complexes with the 1,8-bis(trimethylsilylamido)naphthalene ligand. The molecular structures of complexes [1,8-C10H6(NSiMe3)2YCl(DME)]2(μ-Cl)[Li(DME)3] and {[1,8-C10H6(NSiMe3)2]YN(SiMe3)2(μ-Cl)}2{Li(DME)3}2

The reaction of equimolar amounts of YC1₃ and [1,8-C₁₀H₆(NSiMe₃)₂]Li₂ in THF produced the complex {[1,8-C₁₀H₆(NSiMe₃)₂YCl(DME)]₂(μ-Cl)}[Li(DME)₃] (1), which was isolated by recrystallization from a DME—hexane mixture as yellow crystals in 82% yield. The reaction of complex 1 with (Me₃Si)₂NLi(Et₂0) (in a molar ratio of 1:2) in toluene gave the corresponding amide derivative [1,8-C₁₀H₆(NSiMe₃)₂YN(SiMe₃)₂(μ-Cl)]₂[Li(DME)₃]₂ (2). The recrystallization of the reaction product from toluene afforded complex 2 in 73% yield. The X-ray diffraction study showed that in the crystalline state, compounds 1 and 2 consist of the isolated cationic and anionic moieties. The complex anions are dinuclear moieties with the bridging chlorine ligands.     

Synthesis,structure, and catalytic properties of heteroelement carbene tungsten complexes Ph<Subscript>3</Subscript>ECH=W(OBu-<Emphasis Type="Italic">t</Emphasis>)<Subscript>2</Subscript>(OPh)<Subscript>2</Subscript> (E = Si,Ge)

Novel silicon- and germanium-containing tungsten complexes Ph₃ECH=W(OBu-t)₂(OPh)₂ were synthesized by the reaction of carbyne derivatives Ph₃EC≡W(OBu-t)₃ (E = Si, Ge) with phenol and isolated in high yields. Their structure was determined by X-ray diffraction. Individual complexes do not exhibit catalytic activity, whereas in the presence of AlBr₃ they initiate metathesis polymerization of cyclooctene.