Jolanta Ejfler

Chemoselective alcoholysis of lactide mediated by a magnesium catalyst: an efficient route to alkyl lactyllactate.

Alkyl-(S,S)-O-lactyllactate was prepared by chemoselective alcoholysis of lactide LA mediated by a magnesium catalyst. When ROH reacted with LA it yielded the ring-opened product R-(S,S)-O-lactyllactate exclusively, which remained intact as long as LA was present in the reaction mixture. Consumption of LA caused the reaction to proceed further giving R-(S)-lactate.

Highly efficient magnesium initiators for lactide polymerization

Two monomeric, six-coordinated magnesium complexes with bulky aminophenolate ligands [(Htbpoa)2Mg] (1) and [(Htbpca)2Mg(THF)2] (2), where Htbpoa =N-[methyl(2-hydroxy-3,5-di-tert-butylphenyl)]-N-methyl-N-methyl-1,3-dioxolaneamine and Htbpca =N-[methyl(2-hydroxy-3,5-di-tert-butylphenyl)]-N-methyl-N-cyclohexylamine have been prepared, characterized and employed as initiators for lactide polymerization. The crystal structure of the homoleptic compound 1 has been determined and shows that the six-coordinate magnesium atom in 1 is surrounded by two tridendate tbpoa ligands. In the solution, however, complex 1 exists in equilibrium with a five-coordinate species 1a having one oxolane fragment dangling. The tbpoa and tbpca ligands in 1 and 2 play a dual role, as the ancillary ligand stabilizing the monomeric magnesium species and as the initiating polymerization group.

Novel organic–inorganic hybrids based on T8 and T10 silsesquioxanes: synthesis, cage-rearrangement and properties

In this paper, we present a simple approach for the synthesis of well-defined macromolecules based on precisely isolated amino- and amido-functionalized octa T8 and deca T10 silsesquioxanes (SQs). Here, we show that reorganization of the siloxane cage-like core (T8 → T10) can be easily performed, including isolation of intermediates, and cage rearrangement achieved by using Bronsted superacid, trifluoromethanesulfonic acid (CF3SO3H). Moreover, T10-like SQs can be obtained in a one-step reaction by alkoxysilane condensation in trifluoromethanesulfonic acid conditions. The resulting decamers of amine-SQ and an amido-functionalized derivative containing long alkyl chains are reported for the first time in the literature. The non-fluorinated amido derivatives due to their lamellar-like nature and specific packing can serve as transparent hydrophobic coatings in various industrial applications. The obtained compounds were fully characterized using FT-IR, UV-vis, multinuclear NMR (1H, 13C, 29Si), DOSY NMR, TG-DTA, DSC, HR-MS, TEM, EDS and elemental analysis.

New intermediates for the synthesis of olefin polymerization catalysts: the complexes [M2(µ-Cl)2Cl4(thf)4](M = Ti or V, thf = tetrahydrofuran); crystal structures and properties

The dimeric titanium(III) and vanadium(III) complexes [M2(µ-Cl)2Cl4(thf)4](M = Ti 1 or V 2, thf = tetrahydrofuran) have been prepared by recrystallization of [MCl3(thf)3] from dichloromethane. In the dimers, composed of slightly distorted edge-sharing octahedra, the metal atoms separated by Ti ⋯ Ti and V ⋯ V distances of 3.711 (3) and 3.619(1)A, respectively, are surrounded by two terminal Cl atoms, two oxygen atoms of thf molecules and are linked by two bridging Cl atoms. The geometry around the titanium atoms differs from that around vanadium because the thf molecules and the terminal chlorine atoms are differently located with respect to the bridging chlorine atoms of the M2(µ-Cl)2 unit. High catalytic activity was found for ethylene polymerization by 1.

Lactide as the Playmaker of the ROP Game: Theoretical and Experimental Investigation of Ring-Opening Polymerization of Lactide Initiated by Aminonaphtholate Zinc Complexes

A family of homo- and heteroleptic zinc complexes bearing aminonaphtholate ligands was synthesized and fully characterized. Using NMR spectroscopy and DFT calculation, bis-alkoxy-bridged complexes [LZn(μ-OR)]2 were confirmed to have dimeric structures in solution, analogous to those obtained via X-ray crystallography. Surprisingly, a detailed experimental and theoretical study of the catalytic activity of [LZn(μ-OR)]2 in the ring-opening polymerization (ROP) of lactides showed that although well-defined alkoxy dimers possess a single-site structural motif, the most active initiator is obtained during in situ alcoholysis of the alkylzinc precursor. These results indicate that rational ancillary and alkoxy ligand design that takes into account its mutual interaction on monomer coordination may be key to the synthesis of new high-performance ROP catalysts.

Synthesis and microstructural properties of the scaffold based on a 3-(trimethoxysilyl)propyl methacrylate–POSS hybrid towards potential tissue engineering applications

The aim of this work was to develop an efficient approach to prepare a macroporous scaffold for sophisticated bone replacement, avoiding a long-lasting and complex methodology. Such a scaffold based on the 3-(trimethoxysilyl)propyl methacrylate–POSS hybrid was synthesized via the reaction of 3-(trimethoxysilyl)propyl methacrylate and the trifluoromethanesulfonate–POSS salt. The results show that the chemical composition, structural dimensions, topography, and microstructural properties of the scaffold fulfill the potential requirements for hard-tissue engineering. The microstructural properties were evaluated with the use of X-ray microcomputed tomography (micro-CT) and nanoindentation tests. The former makes it possible to estimate the geometrical measures of the microstructure (porosity, thickness distribution, etc.), whereas the latter makes it possible to estimate the mechanical properties of the constituents of the material (hardness, stiffness modulus, creep, etc.). The aforementioned laboratory testing methods are modern techniques, currently being developed for materials science, making it possible to determine the microstructural/measures of the analyzed system.

Syntheses of new hexacoordinate germanium(IV) complexes. Crystal structures and properties of [GeCl4(TMEDA)] and [GeCl2(N3)2(TMEDA)]

The simple high-yield syntheses and some characterization of new hexacoordinate [GeCl4(TMEDA)] (1) and [GeCl2(N3)2(TMEDA)] (2) are reported. The crystal structures of neutral 1 and 2 are described. Some electronic, geometrical, and thermodynamic features of 1 and 2 were computationally investigated at the B3LYP density functional level of theory.

Synthesis and characterization of new di- and tetra-meric vanadium intermediates of olefin polymerization catalysts. Crystal structures of [V2(µ-Cl)2Cl4(MeCo2Et)4] and [{VOCl2[CH2(CO2Et)2]}4]·2CH2Cl2

The direct reaction of VCl3 and ethyl acetate yields [V2(µ-Cl)2Cl4(MeCO2Et)4]1. The compound [V2(µ-Cl)2Cl4{CH2(CO2Et)2}2]2 was obtained in dichloromethane via the substitution of MeCO2Et in 1 by ethyl malonate. During crystallization of 2, under the influence of dioxygen and moisture, the tetrameric compound [{VOCl2[CH2(CO2Et)2]}4]·2CH2Cl23 was formed. The crystal structures of 1 and 3 have been determined by single-crystal X-ray diffraction studies. The dimeric compound 1 exhibits six-co-ordinate VIII centres [separated by a V ⋯ V distance of 3.590(1)A] surrounded by two terminal Cl atoms, two carbonyl oxygen atoms of co-ordinated ethyl acetate molecules and linked by two bridging Cl atoms. In the tetrameric species 3, the four vanadium(IV) atoms have equivalent octahedral geometries, being bonded by two mutually cis chlorine atoms, two mutually cis oxygen atoms. High catalytic activity was found for 1, 2 and [V2(µ-Cl)2Cl4(thf)4](thf = tetrahydrofuran).

The formation of molecular compounds in the reaction between [MgCl2(THF)2] and [MoCl3O(THF)2]. Crystal structure of [{MoCl4O(THF)}2Mg(THF)4]·CH2Cl2

Abstract The interaction of [MgCl2(THF)2] with [MoCl3O(THF)2] in 1:1 and 1:2 ratios in CH2Cl2 gave the paramagnetic complexes [(THF)3Mg(μ-Cl)3MoCl2O] I and [{MOCl4O(THF)}2Mg(THF)4]·CH2Cl2 II (THF, tetrahydrofuran). In complex I, the molybdenum and magnesium atoms are octahedrally surrounded by three bridging chlorine atoms and terminal oxo-oxygen and two chlorine atoms and by three THF molecules, respectively. Complex II consists of Mg2+ ions coordinated by four THF molecules and two trans[MoCl4O(THF)]− anions coordinated to an Mg atom by oxo O-atoms.

Di-μ-chloro-tetrachlorobis(diethyl o-phthalate)dititanium(III), a new intermediate for the synthesis of titanium(III) compounds: crystal structure and properties

Abstract Di-μ-chloro-tetrachlorobis(diethyl o -phthalate)dititanium(III) tetra(dichloromethane) was obtained by direct reaction of TiCl 4 , diethyl o -phthalate and metallic aluminum in CH 2 Cl 2 . The crystal structure was determined by X-ray diffraction methods and refined by a full-matrix least-squares technique to R = 0.0495 for 2026 independent non-zero reflections. Crystals are triclinic, space group P l, with one complex molecule in the unit cell of dimensions: a = 10.475(8), b = 10.843(9), c = 11.190(12) A, α = 76.91(8), β = 73.39(7), γ = 81.10(7)°. The crystals contain dimeric molecules possessing crystallographic symmetry centres. The titanium(III) ions are octahedrally coordinated by two terminal and two bridging chlorine atoms and two carbonyl oxygen atoms of diethyl o -phthalate. The magnetic susceptibility and ESR measurements revealed an antiferromagnetic exchange interaction between titanium atoms in the dimer.