A. V. Churakov

Ditopic complex formation of the crown-containing 2-styrylbenzothiazole

The complex formation of 2-styrylbenzothiazole containing a 15-crown-5 ether fragment with alkaline earth metal cations, proton, Ag+ and Hg2+ was studied by optical and X-ray diffraction methods. The compound is able to bind the metal cations through the participation of two centers: the crown ether moiety and the heterocyclic part. The alkaline earth metal cations form complexes with the macrocyclic part of the molecule. The formation of a strong sandwich complex was found in the case of Ba2+. The proton coordinates with the N atom of the heterocyclic fragment of the molecule. The Ag+ and Hg2+ cations bind with both centers of the molecule: the crown ether fragment and the heterocyclic residue.

Direct ortho -palladation of 2-phenyl-2-oxazoline: Crystal structure of Cl2Pd(OCH2CH2NCPh)2 and Cl(PPh3)Pd(OCH2CH2NCC6H4)

Direct ortho -palladation of sterically non-hindered 2-phenyl-2-oxazoline ( 1 ) using Pd(OAc) 2 and AcONa in AcOH provided di-μ-acetatobis-[2-(2-oxazolinyl)phenyl,1-C,3-N]dipalladium(II) ( 3a ) in a yield of 63%. Dimeric complex 3a was converted into the corresponding μ-chloro analog ( 3b ) by the reaction with LiCl in acetone in quantitative yield. Compound 3b was also obtained in 90% yield by the ligand exchange reaction of oxazoline ( 1 ) with dimeric ortho -palladated complex of N , N -dimethylbenzylamine in a AcOH–CHCl 3 mixture at 50°C. The same reaction at room temperature provided the coordination complex dichlorobis-(2-phenyl-2-oxazoline)palladium(II) ( 2 ); the use of toluene in this reaction (50°C) led to the formation of chloro[ N , N -dimethylbenzylamino]-(2-phenyl-2-oxazoline)palladium(II) ( 5 ). Dimer 3b reacted with 2,4-pentadionate and PPh 3 to yield the corresponding mononuclear derivatives 6 and 7 , respectively. The structures of coordination complex 2 and phosphane adduct 7 were confirmed by X-ray diffraction analysis. Compound 2 has a centrosymmetric structure with strictly planar coordination environment of the palladium center and a close above-plane approach of the ortho -CH bond to the metal center. In adduct 7 , both the palladium coordination sphere and palladacycle are nearly planar.

Synthesis and resolution of an α-phenyl substituted ortho-palladated matrix

Abstract A novel ortho -palladated benzylaminate matrix bearing phenyl substituent at the α-carbon stereocenter was prepared in the racemic state by direct intramolecular palladation of tertiary diphenylmethylamine with palladium(II) acetate; its structure and palladacycle conformation were determined by 1 H NMR studies of the mononuclear triphenylphosphine adduct. The resolution of the dimeric complex was performed via recrystallization of its diastereomeric ( S )-prolinate derivatives. The absolute configuration ( R C , R C ) of the enantiopure dimer thus obtained was determined by an X-ray diffraction investigation of the less soluble ( R C , S C S N )-diastereomer of its ( S )-prolinate adduct.

Molecular and crystal structure of 4-hexylbenzoic acid: Design of the mesophase

The crystal structure of 4-hexylbenzoic acid C6H13-C6H4-COOH, which forms a nematic mesophase upon melting, is determined. The crystal contains three crystallographically independent molecules. Their molecular skeletons are made up of two almost planar fragments: a benzene ring, π-conjugated with the carboxyl group and a planar zigzag aliphatic fragment. One of the independent molecules forms centrosymmetric dimers via pairs of hydrogen bonds between carboxyl groups, whereas the two others are linked via hydrogen bonds. The dimers in the crystal are packed into pseudostacks with a pronounced nonparallel arrangement of conjugated fragments. There is no good mutual projecting of benzene rings in the stacks, which corresponds to efficient π-stacking interaction. The graph describing the mesophase of this compound contains only one structure-forming element (a hydrogen bond) and corresponds to the nematic mesophase.

On the reduction behaviour of 2-methoxyethyl and 2-methylthioethyl substituted zirconocene dichlorides: crystal structure of (η5,σ-C5Me4CH2CH2S)2Zr

Abstract A reduction of previously reported 2-methoxyethyl and 2-methylthioethyl functionalized zirconocenedichlorides (η5-C5Me4CH2CH2EMe)(η5-C5Me5)(ZrCl2 (E = O, S) and (η5-C5Me4CH2CH2EMe)(η5-C5Me4CH2CH2E′Me)ZrCl2 (E = O, S; E′ = O, S) with Mg/Hg in THF leads unexpectedly to the products of OMe and SMe bond cleavage (η5,σ-C5Me4CH2CH2E)(η5-C5Me5)ZrMe (E = O, S), (η5,σ-C5Me4CH2CH2E)(η5-C5Me4CH2CH2E′Me)ZrMe (E = O, S; E′ = O), and (η5,σ-C5Me4CH2CH2S)2Zr respectively. The crystal structure of (η5,σ-C5Me4CH2CH2S)2Zr was established by X-ray analysis. At that same time the reduction of (ηsu5-C5Me4CH2CH2EMe)(η5-C5Me5)ZrCl2 (E> = O, S) under 1 atm of CO gives either only the dicarbonyl derivative (η5-C5Me4CH2CH2EMe) (η5-C6Me5)Zr(CO)2 (E = O) or a complex mixture of products (E = S).

Tetramethyl(2-methoxyethyl)cyclopentadienyl complexes of zirconium(iv). Crystal structure of [η5:η1−C5(CH3)4(CH2CH2OCH3)]ZrCl3

Several novel zirconium(iv) complexes with the chelating oxygen-containing cyclopentadienyl ligand, tetramethyl(2-methoxyethyl)cyclopentadiene, have been synthesized. [η5:η1-Tetra-methyl(2-methyl)cyclopentadienyl]trichlorozirconium (2), bis[η5-tetramethyl(2-methoxyethyl)cyclopentadienyl]dichlorozirconium (3), [η5-pentamethylcyclopentadienyl][η5-tetra-methyl(2-methoxyethyl)cyclopentadienyl]dichlorozirconium (4), and [η5-tetra-methyl(2-methylthioethyl)cyclopentadienyl][η5-tetramethyl(2-methoxyethyl)-cyclopentadienyl]dichlorozirconium (5) have been prepared from the corresponding lithium cyclopentadienide (l). The crystal structure of cyclopentadienyl complex2 has been established by X-ray analysis. The coordination O→Zr bond in compound2 exists both in the crystalline state and in solutions. No coordination of this type was observed in complexes3–5. Synthesized complexes2–5 are discussed in comparison with their sulfur-containing analogs.

Synthesis of new 2,6-diisobornyl-4-methylphenol derivatives

New 2,6-diisobornylphenol derivatives having formyl, hydroxymethyl, and carboxy groups in the para position with respect to the hydroxy group were synthesized. 4-Hydroxy-3,5-diisobornylbenzoic acid was obtained in a moderate yield through intermediate ortho ester and methyl ester.

Binary palladium carboxylates with electron-donating and electron-withdrawing substituents in the carboxylate ligand: Synthesis and structural studies. The crystal structures of Pd3(μ-CH2ClCO2)6 · CH2Cl2, Pd3(μ-C6H11CO2)6, and Pd3(μ-CMe3CO2)6

Replacement of the acetate ligands in Pd3(μ-MeCO2)6 in benzene gave complexes of the general formula Pd3(μ-RCO2)6 (R = CF3, CCl3, CH2Cl, Me, cyclo-C6H11, and CMe3). The structures of the complexes were determined using IR spectroscopy, ESI mass spectrometry, and X-ray diffraction. It was found that the complexes contain a trinuclear Pd framework and that their spectroscopic and structural parameters depend on the donor-acceptor properties of the substituent in the carboxylate ligand.

Bis(citrato)germanates of bivalent 3d metals (Fe, Co, Ni, Cu, Zn): Crystal and molecular structure of [Fe(H2O)6][Ge(HCit)2] · 4H2O

In continuation of a systematic study of bis(citrate)germanates, we synthesized a number of heterometallic germanium(IV) and 3d metal complexes based in citric acid (H4Cit) with the molecular formula [M(H2O)6][Ge(HCit)2] · nH2O, where M = Fe, n = 4 (I); Co, n = 2 (II); Ni, n = 2 (III); Cu, n = 1 (IV); Zn, n = 3 (V). The complexes were characterized by elemental analysis, X-ray diffraction, thermogravimetry, and IR spectroscopy. The X-ray diffraction analysis of compound I was performed. Crystals are monoclinic, a = 10.091(4) Å, b = 11.126(4) Å, c = 10.996(4) Å, β = 100.966(6)°, V = 1212.1(8) Å3, Z = 4, space group P21/n, R1 = 0.0561 for 2266 reflections with I > 2σ(I). Compound I is composed of centrosymmetric octahedral complexes-[Ge(HCit)2]2− anions and [Fe(H2O)6]2+ cations—and crystallization water molecules. Structural units in compound I are combined by a hydrogen bond system.

Specific features of the structure of germanium(IV) complexes with polybasic acids

The specific features revealed in the structure of germanium(IV) compounds with ligands in the form of anions of polybasic acids (monoamine, diamine, and triamine complexones, i.e., hydroxyethylidene-diphosphonic and carboxylic acids) have been considered. The influence of the individuality of specific acids on the structure type (mononuclear, binuclear, trinuclear, hexanuclear, polynuclear), the coordination mode of monodentate ligands and donor atoms of polydentate ligands (terminal, bridging, chelating, chelating-bridging), and variants of the coordination of polydentate ligands, i.e., anions of polybasic acids, with metal atoms (germanium, rare-earth elements, copper, barium), as well as on the dependence of the Ge-O bond length on the individual nature of ligands (OH, H2O, O(oxo)) and donor atoms of polydentate ligands α- and β-O(carb), O(hydr), O(P)] and their function in the structure (terminal, bridging, chelating, chelating-bridging), has been analyzed using 28 homometallic and heterometallic complexes as an example.