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.
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.
Potential single-source molecular precursors [Ba{(µ-ddbfo) 2 MR x } 2 ] (ddbfoH ) 2,3-dihydro-2,2dimethylbenzofuran-7-ol; M/R/x ) Al/Me/2, Al/Et/2, Ga/Me/2, or Zn/Et/1) for mixed metal oxide materials were prepared by the reaction of barium aryloxide [Ba(ddbfo) 2 (ddbfoH) 2 ] • 3ddbfoH with an appropriate organometallic compound in toluene. The precursors were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray structural analysis. The Ba/Al 2 and Ba/Ga 2 complexes undergo thermal decomposition to give mixed metal oxides BaM 2 O 4 (M ) Al, at 1300 °C for both Me and Et derivatives; Ga, at 1430 °C). Instead, the Ba/Zn 2 complex decomposes to a mixture of BaCO 3 and different metal oxides. The chemical composition and surface morphology of heterobimetallic oxides were analyzed by SEM-EDS and X-ray powder diffraction (XRD) that revealed the formation of highly pure oxide materials with micrometer particle sizes.
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