Hydro- and chloro-substituted silyl- and silyl-η1-amido-η5-tetramethylcyclopentadienyl titanium complexes

Abstract

Complex 9 was also obtained by reaction of 8 with BCl 3 , whereas the same reaction using alternative chlorinating agents (TiCl 4 , HCl) resulted in deamidation to give 2, which was also converted into 3 by reaction with BCl 3 . All of the new compounds were characterized by NMR spectroscopy and the molecular structures of 2 and 4 were determined by X-ray diffraction methods. #

Aryl-imido niobium complexes with chloro-silyl and aryl-η-amidosilyl cyclopentadienyl ligands: X-ray structure of the constrained-geometry compound [Nb(η5-C5H4SiMe2-η1-NAr)(NAr)Cl] (Ar=2,6-Me2C6H3)

“…The selective hydrolysis of the Si-Cl bond with formation of a Si-O-Si bridge was the expected behaviour for this type of niobium compound [11,27]. In contrast, it was observed [6,[30][31][32][33] that the hydrolysis reactions of related monocyclopentadienyl group 4 metal complexes with Scheme 1. the chloro-silylcyclopentadienyl ligand afforded Si-O-M bridges. Attempts to produce further hydrolysis of NbCl bonds failed and led to decomposition products with elimination of the corresponding amine.…”

Synthesis and reactivity of imido niobium complexes containing the functionalized (dichloromethylsilyl)cyclopentadienyl ligand

“…The diastereoisomers were in a 1:0.5 molar ratio and were identified by the two ABCD sets of signals observed in the 1 H NMR spectrum for each C 5 H 4 group and one resonance for each isomer in the 29 Si NMR spectrum at around d À8, very close to that observed for the starting complex 2. The presence of a niobium-amido group was also confirmed by the lowfield shifted resonance above d 8 for the Nb-NHtBu proton compared with the signal shifted highfield (d 1-3) observed for the related aminosilyl Si-NHtBu group.…”

“…In this case, the 1 H NMR spectrum of 5 again showed an AA 0 BB 0 pattern, after recovering the C s symmetry; meanwhile, the 29 Si NMR spectrum showed a resonance shifted highfield (d À29.0), due to the presence of two p donor amido ligands bound to the silicon atom [29,30]. Furthermore, the resonances at low field of the H-N niobium-amido groups disappeared, although the new resonances for the siliconamido ligands could not be observed.…”

“…The 1 H and 13 C NMR spectra of 2 showed signals corresponding to the presence of two different tBu groups, whereas the 1 H and 13 C NMR spectra of 3 only showed signals for one tBu group. The 29 Si NMR spectra were the most useful spectroscopic means to distinguish a silicon-amido bond from a niobium-amido bond in complex 2, the resonance observed at d À9.8 was clearly shifted highfield compared to the values found for compounds 1 and 3, d 12.0 and d 13.4, respectively, supporting the presence of two chloro ligands at the silicon atom.…”

“…These two types of compounds offered the opportunity to introduce a chelating cyclopentadienyl silyl-g-amido ligand whilst still leaving a second reactive point at the cyclopentadienyl ligand. The first type of complex can be illustrated by the reported constrained geometry group 4 metal complexes with one additional Si-X bond (X = H, Cl, NHtBu) [28][29][30], which were suitable to explore further reactivity of these bonds. Furthermore, hydrolysis of the Si-Cl bond of the starting [Ti{g 5 -C 5 R 4 (SiCl 2 Me)}Cl 3 ] (R = H, Me) complexes gave dinuclear compounds with Si-O-Ti [28] bridges and one additional Si-O-Si bridge (for R = Me) [31].…”