Ferrocenes. II. Silicon-Substituted Ferrocenes with Hydrolyzable Functional Groups^1,2

The highly regiospecific synthesis and crystal structure determination of 1,1′-2,5′ substituted ring-locked ferrocenes

“…This particular ferrocenophane is related to (7) and (8) but without the additional 2,5 0 -substitution we report here. Previous methods to make 1,1,3,3-tetramethyl-1,3-disila-2-oxa [3]ferrocenophane have involved the solvolysis of precursors such as 1,1 0 -bis(chlorodimethylsilane)ferrocene [36], 1,1 0 -bis(dimethylsilane)ferrocene [37] or Fe(g 5 -C 5 H 4 SiMe 2 XEt) 2 (where X = O [37] or N [38]. However, Keppler et al have reported an improved synthesis and a new crystal structure for 1,1,3,3-tetramethyl-1,3-disila-2-oxa [3]ferrocenophane from 1,1 0 -dilithioferrocene Á TMEDA and dichlorodimethylsilane in a one-pot reaction [39].…”

Group 4 metallocene complexes with non-bridged and tetramethyldisiloxane-bridged methyl-phenyl-cyclopentadienyl ligands: synthesis, characterization and olefin polymerization studies

“…Tetramethyldisiloxanebridged ansa-metallocenes are an interesting group of complexes. Some lanthanide and group 4 tetramethyldisiloxane-bridged ansa-metallocenes related to the ferrocenophane derivative reported previously [2] have been isolated. We reported [3,4] 2 Cl 2 ] and similar hydrolytic cleavage of SiNMe 2 bonds gave the tetramethylcyclopentadienyl titanium derivative [5].…”

“…Some lanthanide and group 4 tetramethyldisiloxane-bridged ansa-metallocenes related to the ferrocenophane derivative reported previously [2] have been isolated. We reported [3,4] 2 Cl 2 ] and similar hydrolytic cleavage of SiNMe 2 bonds gave the tetramethylcyclopentadienyl titanium derivative [5]. These group 4 metal [6] and similar praseodymium and ytterbium [7] compounds with unsubstituted and t-butyl-substituted [6,8] cyclopentadienyl rings were isolated following the method reported for the first titanium derivative [9], by reaction of the metal halides with the sodium or potassium salts of the dicyclopentadienyl ligand.…”

“…Reaction of 2 equivalents of the dilithium salt 1 with the dichlorodisiloxane [(SiMe 2 Cl) 2 O] in THF afforded the dicyclopentadienylsiloxane [(Me-Ph-C 5 H 3 SiMe 2 ) 2 O] 8, which was isolated as a yellow-orange viscous liquid in 77% yield. Assuming that silicon is always bound to the sp 3 ring-carbon atom, that the methyl and phenyl substituents are located at 2-4 positions with respect to the bridgehead carbon atom and that the silyl group is never located in a position with respect to both methyl and phenyl groups [17], three possible isomers of 8 could be formed.…”

“…Both rings of rac-10a are tilted with an angle between the Cp planes of 50.86°and a Cp(centroid)-Zr-Cp(centroid) angle of 132.74°, comparable to those reported for metallocenes containing nonbridged cyclopentadienyl ligands. This tilting brings the two a-carbons [C (2) ..... C(7)] nearer (3.126 Å ) whereas the distances between the distant carbons [C (4) ..... C(10) and C (5) ..... C(9)] are 5.026 and 4.824 Å , respectively, and those between the middle carbon atoms [C (3) ..... C(6)] and the bridgehead atoms [C(1) ..... C(8)] are 3.942 and 3.563 Å , respectively. This seems to be the most favourable disposition for the large bite of the disiloxane bridge in which the two g 5 -coordinated cyclopentadienyl rings are almost identical, although the C(Cp)-Zr bond distances are significantly spread out in a rather broad range between 2.482(3) and 2.596(3) Å , as a consequence of the asymmetric disposition of the bridge.…”