4-ansa-Metallocene complexes: synthesis of 1,1,4,4-tetramethyl-1,4-disilabutylene-bridged titanocene, zirconocene, and hafnocene derivatives

Abstract

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Reduction of Bis[η5-(ω-alkenyl)tetramethylcyclopentadienyl]titanium Dichlorides: An Efficient Synthesis of Long-Chainansa-Bridged Titanocene Dichlorides by Acidolysis of Cyclopentadienyl-Ring- Tethered Titanacyclopentanes

“…Two central carbon atoms of the ansa-chain are partly disordered, reflecting that the flexibility of the ansa-bridge observed in solution is partially retained even in the solid state. [25] The effect of mobility of the ansa-linking chain on the yield of mononuclear metallocene complexes is even more pronounced in the series of ferrocenophanes with three, four and five bridging methylene groups that were synthesized in 2.5, 0.053 and 0.025 % yields by metathesis of bis(sodiocyclopentadienyl) derivative with FeCl 2 . [23] However, despite high dilution, both rac-and meso-forms of this compound were obtained in only 15 % and 11 % yields by the metathesis of 1,12-bis(lithioindenyl)dodecane with ZrCl 4 in THF and toluene, respectively.…”

“…Solvents were evaporated under vacuum, the oily residue was dissolved in heptane (20 mL) and the solution was cooled in a refrigerator overnight. (9), 461 (23) [M À Cl] , 428 (14), 427 (39), 426 (100) [M À 2 Cl] , 425 (15), 423 (15), 370 (14), 309 (30), 308 (11), 307 (40), 274 (10), 272 (21), 217 (12), 189 (19), 181 (11), 135 (24), 134 (31), 133 (21), 119 (25), 83 (11), 81 (8), 69 (15), 57 (18), 55 (27) Reaction of titanacycles 2 a ± c with hydrogen chloride: Compounds 2 a, 2 b (0.40 g each, 1.0 mmol) and 2 c (0.43 g, 1.0 mmol) were dissolved in hexane (40 mL) and a solution of hydrogen chloride (3 mmol, generated from 5 mL of degassed 98 % H 2 SO 4 and NaCl, 0.174 g, 3.0 mmol) in hexane (50 mL) was added. Concentration and cooling of the heptane solution afforded crude complex 1 a which was washed by ethanol (20 mL) and, after drying, recrystallised from heptane.…”

Synthesis of New Silyl-Bridged Bis(cyclopentadienyl) Ligands and Complexes

“…The general approach employed in this study for the synthesis of mono- and dibridged (bis)Cp ligands was a salt elimination reaction between substituted chlorosilanes and lithiated Cp sources to produce new Si−Cp bonds. The preparation and characterization of 2 is described for the first time, and 4 was prepared as described in the literature . The monobridged (bis)Cp compounds 2 and 4 were used as starting materials for the new dibridged compounds 3 and 5 , respectively.…”

“…Preparation of [ μ , μ - (Me 2 SiCH 2 CH 2 SiMe 2 ) 2 (C 5 H 4 ) 2 ] (5). Deprotonation of 4 with 2 equiv of n BuLi provides the dilithio salt Li 2 [ 4 ], and subsequent reaction with 1 equiv of ClMe 2 SiCH 2 CH 2 SiMe 2 Cl produced the dibridged (bis)Cp compound 5 which has two four-atom bridges (eq 2). The product was isolated after nonaqueous workup by vacuum distillation/sublimation and purified by sublimation to provide 5 as a colorless crystalline solid in fair yield (30%).…”

New Trigonal-Bipyramidal 5-ansa-Zirconocene Derivatives. 1. {2,6-Bis(methylcyclopentadienyl)- pyridine}zirconium(IV) Monochloride Monoalkyls and Dialkyls. Crystal Structure of [Zr{C5H3N(CH2C5H4)2-2,6}(n-C4H9)2], the First Thermally Stable Dialkylzirconocene Containing β-Hydrogens

“…After the discovery of the zirconocene−methylalumoxane (Zr-MAO) systems as powerful catalysts for the isotactic and syndiotactic polymerization of propylene, a great deal of scientific work on the explanation of the factors affecting the stereospecificity − and on the relationship between the structures of these systems and the chain growth of the polymer 16 has been promoted worldwide. With the aim of realizing high activity and stereoselectivity of the catalysts and of yielding high-molecular-weight polymers, a number of new ansa -zirconocenes have been synthesized. − …”