154789-31-8Relevant academic research and scientific papers
Pentamethylcyclopentadienylmethyltitanium silsesquioxanes and their zwitterionic complexes with tris(pentafluorophenyl)borane
Varga, Vojtech,Pinkas, Jiri,Cisarova, Ivana,Horacek, Michal,Mach, Karel
, p. 6944 - 6956 (2009)
Reaction of [(η5-C5Me5)TiMe 3] with [(c-C5H9)7Si 8O12(OH)] (SIPOSS) or [(c-C5H9) 7Si7O9(OSiMe3)(OH)2)] (DIPOSS') affords stoichiometrically the half-sandwich titanium-disiloxy-methyl complexes [(η5-C5Me5){(c-C5H 9)7Si8O12O)2TiMe] (1) and [(η5-C5Me5){(c-C5H 9)7Si7O9(OSiMe3)O 2)TiMe] (2), respectively. Compound 2 consists of the two stereoisomers possessing the (η5-C5Me5) ligand and OSiMe3 group in syn- (2a) and anti-position (2b). The more abundant 2a (2a/2b ≈2:1) was isolated by fractional crystallization. Compounds 1 and 2a reacted rapidly with B(C6F5) 3 to give zwitterionic complexes [(η5-C 5Me5){(c-C5H9)7Si 8O12O}2Ti](+)[(μ-Me)B(C 6F5)3](-) (3) and syn-[(η5C5Me5){(c-C5H 9)7Si7O9(OSiMe3)O 2}Ti]{+)[(μ-Me)B(C6F5) 3](-) (4a), respectively. Infrared spectra proved that 3 and 4a were thermally stable in the solid state and the structure of 4a was determined by X-ray single-crystal analysis. In contrast, 1H, 13C and 19F NMR spectra of 3 in toluene C 7D8 revealed that it was completely dissociated into initial components at 25 °C; however, the features of 3 were dominating already at -35 °C. On the other hand, 4a was dissociated only slightly at 25 °C. Stable ionic complexes 7 and 8 were prepared by reacting [PhNHMe 2]+[B(C6F5)4] - with 1 and 2, respectively. Both 7 and 8 contained the molecule PhNMe2 coordinated to the titanium cation and 8 consisted of the syn- and anti-isomers 8a and 8b in abundances found for 2a/2b. Analogous reaction of 1 and 2 with [Ph3C]+[B(C6F5) 4]- afforded impure ionic complexes 9 and 10. When dissolved in the presence of PhNMe2, the amine coordinated to the titanium cations, thus reproducing complexes 7 and 8a/8b, identified by 1H NMR spectra. All compounds 1-10 were inactive in polymerization of styrene to syndiotactic polymer. A low activity was achieved by adding of 2 equiv of AlMe3 to 3 or 4.
