Kirill V. Zaitsev

Titanium complexes based on chiral enantiopure dialkanolamines: synthesis, structures and catalytic activity

New chiral enantiopure tridentate ligands (dialkanolamines) RN(CHR3CR1R2OH)(CHR4CR5R6OH) 10–17 were synthesized by the opening of the epoxide ring by the action of the amines or alkanolamines. Titanium complexes, viz. [RN(CHR3CR1R2O)(CHR4CR5R6O)]Ti(O-i-Pr)218–23 and [RN(CHR3CR1R2O)(CHR4CR5R6O)]2Ti 25–31 were synthesized by treatment of Ti(O-i-Pr)4 with one or two equivalents of corresponding dialkanolamines. Complex (R)-PhCH(Me)N(CH2C(Me)2O)2TiCl2*HNMe224 was obtained from the reaction of one equivalent of dialkanolamine 10 with (Me2N)2TiCl2. The composition and structure of all novel compounds were established by 1H and 13C NMR spectroscopy as well as elemental analysis. The possible solution structures of 18–31 are discussed. The single-crystal X-ray diffraction study of 23, 25–28, 30, 31 indicates monomeric structures in the solid state. Chiral complexes 20, 22, 23, 25, 26, 30 were tested as chiral catalysts in the Abramov reaction and demonstrated moderate enantiomeric activity.

Reaction of digermanes and related Ge-Si compounds with trifluoromethanesulfonic acid: synthesis of helpful building blocks for the preparation of Ge-Ge(Si)-catenated compounds

Abstract The reaction of a series of compounds, Ar3 Ge-MR3, 1–4 (Ar=Ph, p-Tol, M=Si, Ge, R=Ph, Me, tBu), with one equivalent of trifluoromethanesulfonic acid (HOTf) was investigated. The corresponding triflates were isolated in several cases. The molecular structure of Ph3 Ge-GePh2 OTf (5) in solid state was investigated by X-ray analysis. The triflates were converted to the corresponding chlorides under the action of ammonium chloride.

Molecular Oligogermanes and Related Compounds: Structure, Optical and Semiconductor Properties

The optical (UV/Vis absorbance, fluorescence in the solid state and in solution) and semiconducting properties of a number of di- and trigermanes as well as related silicon- and tin-containing germanes, 1-6 ((p-Tol)3 GeGeMe3 (1), Ph3 SnGe(SiMe3 )3 (2), (C6 F5 )3 GeGePh3 (3), (p-Tol)3 GeSiMe2 SiMe3 (4), (p-Tol)3 GeGeMe2 Ge(p-Tol)3 (5), (p-Tol)3 GeSiMe2 SiMe2 Ge(p-Tol)3 (6)) were investigated. Molecular structures of 5 and 6 were studied by X-ray diffraction analysis. All compounds displayed luminescence properties. In addition, a band gap (of about 3.3 eV) was measured for compounds 1-6 showing that those molecules display semiconductor properties.

Syndiospecific polymerization of styrene in the presence of new titanium complexes with dialkanolamines: Titanocanes and bistitanocanes

The syndiospecific polymerization of styrene is studied in the presence of titanium complexes with dialkanolamines—bistitanocanes and titanocane—activated by individual MAO or the combined cocatalyst MAO/TIBA. It is shown that these catalysts are more active and stereospecific after their activation with the combined cocatalyst ([TIBA]: [MAO] ≤ 0.13) than that in the case of the activation with MAO: The activities of the catalysts are ≤18 and 9 kg PS/(mol Ti h), and the syndiotacticities of PS are ≤76 and 60%, respectively. Polymers synthesized in the presence of bistitanocanes are characterized by M n ≤ 4.5 × 104 and T m ≤ 268°C and a narrow molecular-mass distribution (≤2.5).

Enumeration of carboxyl groups carried on individual components of humic systems using deuteromethylation and Fourier transform mass spectrometry

AbstractHere, we report a novel approach to enumeration of carboxylic groups carried by individual molecules of humic substances using selective chemical modification and isotopic labeling (deuteromethylation) and high-resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR MS). Esterification was conducted with a use of thionyl chloride–deuteromethanol reagent under mild conditions to avoid transesterification. The deuteromethylated products were subjected to solid phase extraction using PPL Bond Elute cartridges prior to FTICR MS analysis. An amount of carboxyl groups in the individual molecular component was estimated from the length of identified deuteromethylation series. The method allowed for discerning between compounds with close elemental compositions possessing different protolytic properties. We found that different carboxylic moieties occupy distinct regions in molecular space of humic substances (HS) projected onto Van Krevelen diagram. These locations do not depend on the source of the humic material and can be assigned to carboxyl-rich alicyclic molecules (5 to 6 COOH), hydrolyzable tannins (3-4 COOH), lignins (1 to 2 COOH), condensed tannins and lignans (0 to 1 COOH), and carbohydrates (0 COOH). At the same time, the alignment pattern of these carboxylated species along the structural evolution lines in Van Krevelen diagrams was characteristic to the specific transformation processes undergone by the humic materials in the different environments. The obtained data enable mapping of molecular ensemble of HS with regards to their specific acidic compartments and might be used for directed fractionation of HS. Graphical abstractSelective isotopic labeling followed by FTICR MS enables discerning between humic molecules with close elemental compositions carrying different numbers of carboxylic groups.

Synthesis, structure, and catalytic activity of new aluminum and titanium complexes based on aminobisphenolate ligands containing bulky substituents

A reaction of aminobisphenols EtN{CH2[(4-Alk)(6-But)(2-HO)C6H2]}2, Alk = Me (1); But (2) containing alkyl substituents in the phenol groups with trimethylaluminum and tetra(tert-butoxy)titanium gave two new aluminum derivatives with the Me–Al bond: EtN{CH2[(2-Alk)-(4-But)C6H2(2-O–)]}2Al–Me, Alk = Me (3); But (4), and two new titanium derivatives with the ButO–Ti bond: EtN{CH2[(2-Alk)(4-But)C6H2(2-O–)]}2Ti(O–But)2, Alk = Me (5); But (6). The structures of new compounds were confirmed by NMR spectroscopy and elemental analysis. The structures of complexes 3 and 6 were studied by X-ray crystallography. Complexes 3 and 6 are monomeric in the solid phase: a coordination number of Al atom is 4, that of Ti atom is 5, in addition to the M–O bonds the M←N interactions are also present. Complexes 3–6 were studied as initiators of the ring-opening polymerization of ε-caprolactone. The resulting polymers are characterized by relatively high values of number average molecular weight, with the polydispersity being relatively low.

Controlled homoand copolymerization of ε-caprolactone and d,l-lactide in the presence of TiIV complexes

Titanium complexes with dialkanolamine (1, 2) and salen ligands (3), as well as titanium alkoxide containing two fragments of an unsaturated alcohol (cis-but-2-ene-1,4-diol) asε-ligands (4), were studied in the anionic ring-opening bulk polymerization of ɛ-caprolactone (CL) at 80–130 °,C. All the catalysts involved initiate controlled polymerization and afford polyesters with a number-average molecular weight up to Mn = 20 000 g mol−1, which can be regulated by adjusting the [monomer]: [catalyst] ratio. Among the catalysts studied, complex 2 is most efficient in CL polymerization and affords polyesters with the narrowest molecular weight distribution (Mw/Mn < 1.2). In addition, complex 2 initiates the controlled polymerization of d,l-lactide (LA) and is effective in the synthesis of random and block copolymers of CL and LA.

Synthesis, structure, and catalytic activity of new aluminum complexes formed with sterically bulky ligands

A reaction of pyridine related ligands containing two hydroxyalkyl groups, 2,6-(HO-Z-CH2)2C5H3N (Z is 1,1-cyclohexylene, 2,2-adamantylene) with trimethylaluminum and trimethoxyaluminum leads to three new aluminum complexes with the Me-Al or MeO-Al bond: 2,6-C5H3N(CH2-Z-O)2Al-X (Z is 1,1-cyclohexylene, X = Me (5), OMe (6); Z is 2,2-adamantylene, X = Me (7)). The structures of new derivatives were confirmed by NMR spectroscopy and elemental analysis. The structure of complex 5 was studied by X-ray diffraction analysis. Complex 5 is a dimer in the solid state due to the formation of a four-membered ring...Al-O...Al-O.... Complexes 5 and 6 were studied as initiators of the ring-opening polymerization of ε-caprolactone.

Di-μ-oxido-bis­({2,2′-[ethane-1,2-diylbis(nitrilo­methanylyl­idene)]diphen­olato}titanium(IV)) chloro­form disolvate

In the title compound, [Ti2(C16H14N2O2)2O2]·2CHCl3, the TiIV atom in the centrosymmetric complex has a distorted octahedral N2O4 coordination environment and is linked via two μ2-oxido bridges into a dinuclear centrosymmetric complex, with a Ti⋯Ti separation of 2.7794 (8) Å. In the salen (N,N′-ethylenebis(salicylimine)) ligand, the two salicylimine units make a dihedral angle of 45.31 (5)°. The complex molecules are stacked parallel to [100], forming channels in which the solvent chloroform molecules are located. C—H⋯O hydrogen-bonding interactions between the complex molecules and the solvent molecules consolidate the crystal packing.

{2,2′-[Ethane-1,2-diylbis(nitrilo­methan­yl­yl­idene)]diphenolato}(iso­propano­lato)aluminium di­chloro­methane hemisolvate

In the title compound, [Al(C16H14N2O2)(C3H7O)]·0.5CH2Cl2, the salen complex is monomeric and the dichlormethane solvent molecule lies on a crystallographic twofold axis. The central Al atom is fivefold coordinated and possesses a square-based pyramidal environment. The Al—OAlk(ipropyl) bond [1.7404 (14) Å] is much shorter than the Al—OAr(salen) bond lengths [1.7974 (15) and 1.8094 (14) Å]. The isopropyloxo group forms an intramolecular C—H⋯N hydrogen bond. In the crystal, the complex molecules are linked by weak C—H⋯O interactions.