Lucjan B. Jerzykiewicz

Syntheses, structure, and reactivity of chiral titanium compounds: procatalysts for olefin polymerization.

Titanium complexes with chelating alkoxo ligands have been synthesised with the aim to investigate titanium active centres in catalytic ethylene polymerisation. The titanium complexes cis-[TiCl2(eta2-maltolato)2] (1, 89%), and cis-[TiCl2(eta2-guaiacolato)2] (2, 80%) were prepared by direct reaction of TiCl4 with maltol and guaiacol in toluene. The addition of maltol to [Ti(OiPr)4] in THF results in the formation of species [Ti(OiPr)2(maltolato)2] (3, 82%). The titanium compound cis-[Ti(OEt)2(eta2-maltolato)2] (4, 74%) was obtained by the transesterification reaction of species 3 with CH3CO2Et. When compound 4 is dissolved in THF a dinuclear species [Ti2(mu-OEt)2(OEt)4-(eta2-maltolato)2] (5, 45%) is formed. Reaction of [Ti(OiPr)4] with crude guaiacol in THF yields a solid, which after recrystallisation from acetonitrile gives [Ti4(mu-O)4(eta2-guaiacolato)] x 4CH3CN (6, 55%). In contrast, reaction of TiCl4 with crude guaiacol in tetrahydrofuran affords [Ti2(mu-O)Cl2(eta2-guaiacolato)4] (7, 82%). Crystallographic and electrochemical analyses of these complexes demonstrate that maltolato and guaiacolato ligands can be used as a valuable alternative for the cyclopentadienyl ring. These complexes have been shown to be active catalysts upon combination with the appropriate activator.

New insights into the chemistry of oxomolybdenum(VI) complexes with N-salicylidene-2-aminoethanol

Abstract Oxomolybdenum(VI) complexes with tridentate Schiff base, N -salicylidene-2-aminoethanol (H 2 sae), has been synthesised by the reaction of Mo(O) 2 (sal) 2 (where Hsal=salicylic aldehyde) with 2-aminoethanol. This reaction leads to dimeric [MoO(μ-O)(sae)] 2 and new monomeric [Mo(O) 2 (sae){1,2-O (−) C 6 H 4 C(H)N (+) (H)C 2 H 4 OH}] ( 1 ) compounds. Also substitution of acetylacetonate ligand in Mo(O) 2 (acac) 2 by H 2 sae in EtOH leads to the same complexes (vide infra), but in MeOH monomeric compound Mo(O) 2 (sae)(MeOH) ( 2 ) was formed. The molecular structure of complexes 1 and 2 have been determined by X-ray studies, which confirm that one of the H 2 sae co-ordinates as η 3 -tridentate O,N,O′ ligand, while in complex 1 this ligand exists also in zwitterionic form with intramolecular hydrogen bonding, O⋯HN, 2.584(3) A, of phenolic oxygen bonded to the molybdenum atom. The crystals of 1 are triclinic, space group P 1 , a =8.483(2) A, b =10.187(3) A, c =11.034(3) A, α =105.26(2)°, β =95.29(2)°, γ =95.10(2)°, and D calcd =1.666(1) g cm −3 for Z =2. The crystals of 2 are monoclinic, space group P 2 1 / c , a =6.697(2) A, b =7.375(2) A, c =24.100(3) A, β =92.76(5)°, and D calcd =1.805(1) g cm −3 for Z =4.

Study of complex formation with 2-hydroxyiminocarboxylates: specific metal binding ability of 2-(4-methylthiazol-2-yl)-2-(hydroxyimino)acetic acid

Abstract Complex formation properties of a novel water soluble thiazolyloxime 2-(4-methylthiazol-2-yl)-2-(hydroxyimino)acetic acid (H3L1) with Cu2+ and Ni2+ were investigated in solution by potentiometrical and spectral (UV–Vis, EPR, NMR) methods. All Cu2+ and most of Ni2+ complex species detected in solution were found to have square-planar MN4 core with oxime and heterocyclic nitrogen atoms which was rationalized in terms of destabilizing effect of repulsive interaction between oxygen atom of carboxylic group and nitrogen atom of thiazole ring in N,O-coordinated ligand conformation. It has been found that stability of metal complexes in a series of oxime ligands is dependent upon basicity of nitrogen atom of oxime group. The thiazolyloxime forms less stable complexes with Cu2+ but stronger ones with Ni2+ ions when compared to parent 2-(hydroxyimino)propanoic acid. The lower stability obtained for Cu2+ complexes was elucidated in terms of negative inductive effect of the thiazole and nitrile substituents as well as an effect of intramolecular attractive interaction between thiazolyl sulfur and oxime oxygen atoms in thiazolyloxime. In the case of Ni2+ the complexes formed are square-planar and it is why thiazolyl ligand is more effective in metal ion binding than simple 2-(hydroxyimino)propanoic acid forming only octahedral species. The solid state structure of the Co3+ complex K3[Co(HL1)3]·5.5H2O (1) was studied by X-ray analysis. The thiazolyloxime ligand is coordinated to Co3+ via oxime nitrogen and carboxylate oxygen atoms forming five-membered chelate rings.

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.

Syntheses, structure, and properties of a manganese-calcium cluster containing a Mn4Ca2 core.

We describe here a novel, simple, efficient self-assembly method for the in situ generation of [Mn4Cl4(micro-OCH2CH2OMe)4(EtOH)4] and [Mn4(micro-Cl)Cl3(micro-OCH2CH2OMe)4(HOCH2CH2OMe)3]2 cubane-type compounds which react readily with calcium species to form cluster [Mn4Ca2Cl4(micro-OCH2CH2OMe)8], the calcium atoms attached to the Mn4 unit of flatten out the cubane inducing significant conformational changes.

THE QUASI-SYMMETRIC OHN AND ODN BRIDGES IN THE ADDUCTS OF 3,5-DIMETHYLPYRIDINE WITH 3,5-DINITROBENZOIC ACID

Abstract The crystal structure of the adduct of 3,5-dimethylpyridine and 3,5-dinitrobenzoic acid (DMP-DNB) has been determined at room temperature and 80 K for both undeuterated and deuterated compounds. The monoclinic crystals are isomorphous, space group P 2 1 c and Z = 4. Very strong OHN hydrogen bonds are almost linear with fully disordered (1:1) bridge hydrogen atoms between oxygen and nitrogen atoms. This is well reflected in the difference in electron density maps the contours of which depend both on cooling and deuteration. The intramolecular hydrogen bond lengths are 2.550(2) A for the (OHN) and 2.563(2) A for (ODN) at room temperature and 2.529(2) A for (OHN) and 2.531(2) A for (ODN) at 80 K. Therefore, there is a small but meaningful isotope effect upon the O…N hydrogen bridge length at room temperature and no Ubbelohde isotope effect is observed at 80 K. The infra-red spectra show very broad stretching protonic bands in the 200–1600 cm −1 range. The isotopic ratio v( H ) v( D ) at room temperature is about 1.1.

Reaction of nickelocene with methyllithium in the presence of 2-butyne

Reaction of nickelocene with methyllithium in the presence of 2-butyne at the molar ratio of reactants 1:1:1 leads to the formation of several organinickel compounds. Five of these products were isolated and identified. A novel, 49-electron tri(cyclopentadienylnickel) nickel cluster (CpNi) 3 ·(CH 3 CCCH 3 ) ( 5 ) was fully characterized by spectroscopic and X-ray measurements. Alkyne ligand is bonded to three nickel atoms via two σ and one π bonds (2σ+π bond system). Compound 5 crystallizes from hexane in a monoclinic crystal system and P 2 1 / n space group. Corresponding unit cell parameters were determined as a =9.015(2) A; b =14.608(3) A; c= 13.983(3) A; β =108.47(3)°; V =1746.6(6) A 3 ; Z =4.

Contribution of Energy Transfer from the Singlet State to the Sensitization of Eu3+ and Tb3+ Luminescence by Sulfonylamidophosphates

A series of stable lanthanide complexes Na[Ln(L)4 ] (Ln=La3+ , Eu3+ , Gd3+ , Tb3+ , with L=dimethyl(4-methylphenylsulfonyl)amidophosphate and dimethyl-2-naphthylsulfonylamidophosphate) were synthesized. The compounds were characterized by single-crystal X-ray diffraction, IR, absorption, and emission spectroscopy at 293 and 77 K. In contrast to the usual and well-known dominant role of the ligand triplet state in intramolecular energy transfer processes in Ln complexes, in this particular new class of Ln compounds with sulphonylamidophosphate ligands, strong experimental and detailed theoretical evidence suggest a dominant role is played by the ligand first excited singlet state. The importance of the role played by the 7 F5 level in the case of the Tb3+ compound in this process is shown. The theoretical approach for the energy transfer rates was successfully applied to the rationalization of the experimental data. The higher-lying excited levels of Eu (5 DJ , 5 LJ , 5 GJ ) and Tb (5 DJ , 5 GJ , 5 LJ , 5 HJ , 5 FJ , 5 IJ ) were included in the calculations for the first time. Both the multipolar and exchange mechanisms were taken into account. The experimental intensity parameters (Ωλ ), emission lifetimes (τ), radiative (Arad ) and non-radiative (Anrad ) decay rates, and quantum yields (theoretical and experimental) were determined and are discussed in detail.

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.

Synthesis and structure of the mixed ligand complex of copper(II), bis(9, 10-dihydro-9-oxo-10-acridineacetato)bis(imidazole)copper(II) tetrahydrate

Abstract The new ternary compound Cu(CMA)2(Him)2·4H2O (where CMA−=9,10-dihydro-9-oxo-10-acridineacetate ion) has been synthesized and investigated by X-ray analysis, UV–Vis, EPR, IR and Raman spectroscopy. Magnetic susceptibility was measured in the range 4–300 K. The crystal structure consists of neutral monomers Cu(CMA)2(Him)2 linked by intermolecular hydrogen bonds with water molecules. The copper(II) ion is in a tetragonally elongated octahedral O2N2O′2 environment. Magnetic and spectroscopic results support the X-ray data.