ansa-Metallocene derivatives

Abstract

Titanocene and zirconocene complexes with a phenyl or I-naphthyl substituent in one ,B-position of each Cs-ring ligand and with an interannular tetramethylethano-or dimethylsilano-bridge have been prepared. Racemic complex isomers, which are formed together with varying amounts of their meso isomers, were separated from the latter and characterised by lH NMR spectroscopy and X-ray crystallographic studies. * For Part XXII see ref. 15.

Synthesis and characterization of methyl-phenyl-substituted cyclopentadienyl zirconium complexes

“…The 1 H and 13 C NMR spectra of this mixture (see Section 4) are consistent with the 1 H NMR spectra reported [13] for the meso-9a and rac-9a diastereoisomers. Repeated recrystallization of the first yellow solid fraction from toluene allowed isolating the less soluble 9b as a yellow crystalline solid, although it was always contaminated by variable very small amounts of meso-9a of intermediate solubility.…”

“…As shown in Eq. (1) ] (rac-9a and meso-9a) reported previously [13] together with a third isomer 9b in a molar ratio of ca. 2:2:1, respectively.…”

“…The lithium salt of the disubstituted 1-phenyl-3-methyl-cyclopentadiene Li H 3 ] (1) has been prepared and reacted in situ [13] with dichlorodimethylsilane to prepare the dimethylsilyl-bis (2-methyl-4-phenyl-cyclopentadiene), which was further deprotonated and used for the subsequent formation of the corresponding dimethylsilyl-bridged metallocenes. With the aim of isolating the CG-type silyl-g-amido complexes of this disubstituted methyl-phenyl-cyclopentadienyl ligand, it was convenient to isolate all of the intermediate cyclopentadienes and their lithium salts involved in that procedure (see Scheme 1).…”

“…It has been reported [13] that THF solutions of the dilithium salt 7 prepared and used in situ reacted with ZrCl 4 AE 2THF to give a mixture of diastereomers (rac:meso, 1:1 from the crystallized solid and further extraction from the mother liquor). The presence of 7b in the mixture of isomers contained in the dilithium salt 7 moved us to try to isolate its corresponding zirconium complexes.…”

“…Although some stereochemical mechanistic studies on different transition metal complexes with the 1-phenyl-3-methyl-cyclopentadienyl ligand had been reported previously [11,12], this ligand was used [13] to prepare the first group 4 ansa-metallocenes with tetramethylethylene and dimethylsilyl bridges. Similar disubstituted tetrahydroindenyl compounds have been reported [14] recently.…”