Piotr Sobota

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.

The crystal structure of tetrachloro(diethylphthalate)titanium(IV)

Abstract The crystal structure of [C 6 H 4 (OCOC 2 H 5 ) 2 TiCl 4 ], which in the presence of activators is a good catalyst for olefin polymerization, has been determined by X-ray diffraction methods and refined by full-matrix least-squares techniques to R = 0.045 for 2000 independent non-zero reflexions. Crystals are orthorhombic, space group Pnma , with four molecules in a cell of dimensions: a 11.45(1), b 14.07(1), c 10.56(1) A. The structure consists of discrete molecules possessing crystallographic m ( C s ) point symmetry. The Ti atoms are octahedrally coordinated by four chlorine atoms and two carbonyl oxygen atoms of diethylphthalate. The chelating ligand atoms together with the titanium atom form a seven-membered ring with the Cl and Ti atoms located above the benzene ring.

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.

Interaction between TiCl4 and o-, m- and p-diesters. The crystal structures of [o-C6H4(COO-i-Bu)2TiCl4] · CH2Cl2 and [p-C6H4(COOMe)2TiCl4]

Abstract The crystal structures of [ o -C 6 H 4 (COO-i-Bu) 2 TiCl 4 ] · CH 2 Cl 2 , I, and [(μ-Cl) 2 {μ- p -C 6 H 4 (COOMe) 2 }Cl 6 Ti 2 ] ∞ , II, which in the presence of activators are good catalysts for olefin polymerization, have been determined by X-ray diffraction methods and the data refined by full-matrix least-squares techniques to R = 0.049 and R = 0.028 for 1511 and 1549 independent non-zero reflections for I and II, respectively. Crystals of I are orthorhombic, space group P 2 1 2 1 2 1 with 4 molecules in a unit cell of dimensions a = 14.408(6), b = 13.717(7), c = 12.486(5) A. Crystals of II are monoclinic, space group P 2 1 / n , with four molecules in cell with a = 8.474(5), b = 13.130(7), c = 9.362(7) A and β = 109.12(5)°. The Ti atoms in I are octahedrally coordinated by four chlorine atoms and two carbonyl oxygen atoms of di-iso-butyl o -phthalate. The chelating ligand atoms and the titanium atom together form a seven-membered ring. Compound II in crystalline state is a linear polymer formed by the dimeric units Cl 3 Ti(μ-Cl) 2 TiCl 3 connected together by two carbonyl oxygen atoms of p -C 6 H 4 (COOMe) 2 .

Insertion of CO2 into the metal—nitrogen bond formed in the reaction with molecular nitrogen

Abstract The fixation reaction of carbon dioxide was examined in the following systems; MCl 4 MgTHFN 2 (M = Ti, V) and Cp 2 TiCl 2 MgTHFN 2 . In these systems insertion of CO 2 into the metal—nitrogen bond has been found, which results in the formation of the isocyanate compounds [(THF) 3 Cl 2 Mg 2 OM(NCO)] and Cp 2 TiNCO. In the Cp 2 TiCl 2 MgTHFN 2 CO 2 system the Cp 2 Ti(CO) 2 carbonyl was also formed.

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.

Preparation and crystal structures of the mononuclear vanadium phenoxide complexes [VCl(OC6H3Pri2-2,6)2(C4H8O)2] and [VO(OC6H3Pri2-2,6)3]: procatalysts for ethylene polymerisation

Abstract The complexes [VCl(OC 6 H 3 Pr i 2 -2,6) 2 (thf) 2 ] 1 (thf, tetrahydrofuran) and [VO(OC 6 H 3 Pr i 2 -2,6) 3 ] 2 have been prepared and structurally characterised. Compound 1 has a distorted trigonal bipyramidal structure with apical thf ligands [d(V–O phenox ) 1.865(2), d(V–O thf ) 2.120(3) and d(V–Cl) 2.277(2) A]. It reacts with Li[SC 6 H 2 Me 3 -2,4,6] to give [V(SC 6 H 2 Me 3 -2,4,6)(OC 6 H 3 Pr i 2 -2,6) 2 (thf) 2 ]. Compound 2, which has trigonal pyramidal geometry, is disordered about a 2-fold crystallographic axis [d(V=O) 1.564(4), d(V–O av ) 1.761(1) A]. Compounds 1 and 2 are pro-catalysts for the polymerisation of C 2 H 4 .

Formation of a nitrogen—carbon bond from N2 and CO. Influence of MgCl2 on the N2 reduction process in the system TiCl4/Mg

Abstract TiCl 4 (THF) 2 is reduced by Mg in tetrahydrofuran under N 2 to TiNMg 2 Cl 2 (THF) (I), which reacts further with CO. As a result, TiCONMg 2 Cl 2 (THF) is obtained, which reacts with CH 3 I to produce (CH 3 ) 2 NCOCH 3 in 73% yield. This is indicative of the amide character of nitrogen in I. Upon reaction with I 2 , the amide nitrogen in I is oxidized to imide. The new compound, TiNMgCl(THF) (II), was found to form Ti(NCO)MgCl(THF) on reaction with CO. TiCl 4 (THF) 2 , recognized as a strong Lewis acid, detaches one Cl − from MgCl 2 (THF) 2 formed in the reaction. The [MgCl(THF) n ] + cation influences the N 2 reduction and determines the amide character of the nitrogen atom in species I.

MgCl2 - one of the factors controlling the mechanism of the reaction between grignard reagents and titanium or zirconium tetrachloride. II

Summary Treatment of a Grignard reagent of [MgR 2 (THF) 2 ] with zirconium or titanium tetrachloride gives [MgCl 2 (THF) 2 ], which when treated with [MCl 4 (THF) 2 ] (M = Ti or Zr) yields the compounds: [Mg(THF) 6 ][ZrCl 6 ] (I), [Mg(THF) 6 ][ZrCl 5 (THF)] 2 (II), [Mg(THF) 6 ][TiCl 5 (THF)] 2 ] (IV), [(THF) 4 Mg(μ-Cl) 2 TiCl 4 ] (V) and [Mg 2 (μ-Cl) 3 (THF) 6 [TiCl 5 (THF)] (VI), along with MR 4 . The zirconium compounds I and II are insoluble in THF, which results in a decrease of the ZrR 4 yield. The titanium compounds IV, V and VI are transient intermediates in the formation of TiR 4 .

TiIV and Mov complexes with diesters. The crystal structure of [o-C6H4(CO2CH2CH2Ph)2Cl4Ti], [C2O4(CH2CH2Ph)2Cl4Ti] and [o-C6H4(CO2Et)2Cl3MoO] · C6H6

The crystal structures of [o-C6H4(CO2CH2CH2Ph)2Cl4Ti] (I), in the presence of activators a good catalyst for olefin polymerization, [C2O4(CH2CH2Ph)2Cl4Ti] (II) and [o-C6H4(CO2Et)2Cl3MoO] (III), have been determined by X-ray diffraction methods and refined by a full-matrix least-squares technique to R = 0.036, 0.041 and 0.055 for 2775, 2437 and 2776 independent non-zero reflections for I, II and III, respectively. The crystals of I are triclinic, space group P1 with two molecules in a unit cell of dimensions a = 10.475(8), b = 10.078(9), c = 13.683(9) A, α = 88.75(7) β = 72.65(6) γ = 66.95(7)°. The crystals of II are monoclinic, space group P21/c, with four molecules in a cell with a = 10.045(8), b = 21.032(22), c = 13.193(9) A, β = 128.91(6)°. The titanium atoms in I and II are octahedrally coordinated by four chlorine and two carbonyl oxygen atoms of coordinated o-diester molecules in the cis position. The crystals of III are triclinic, space group P1, with two molecules in a unit cell of dimensions a = 9.722(12), b = 8.073(12), c = 15.683(21) A, α = 83.46(9), β = 75.81(9), γ = 67.74(9)°. Three Cl atoms, one oxo oxygen and two O atoms of the carbonyl groups form a distorted octahedron around the molybdenum atom. The chelate ligand atoms and the titanium atom in I or molybdenum atom in III form a seven-membered ring which is five-membered in II.