215451-37-9Relevant academic research and scientific papers
Untypical regioselectivity of carbon dioxide coupling with titanocene complexes of phenyl(trimethylsilyl)acetylene by using the meso-1,2-ethylene-1,1′-bis(η5-tetrahydroindenyl) ligand system
Thomas, Dominique,Peulecke, Normen,Burlakov, Vladimir V.,Baumann, Wolfgang,Spannenberg, Anke,Kempe, Rhett,Rosenthal, Uwe
, p. 1495 - 1502 (2008/10/08)
The reaction of [meso-(ebthi)TiCl2] [ebthi = 1,2-ethylene-1,1′-bis(η5-tetrahydroindenyl)] with magnesium in the presence of the alkynes Me3SiC≡CSiMe3 and PhC≡CSiMe3 resulted in the formation of the complexes [meso-(ebthi)Ti(η2-Me3SiC2SiMe 3)] (1) and (meso-(ebthi)Ti(η2-PhC2SiMe3)] (2a and 2b), which were isolated and then characterized by their NMR spectra. Due to incomplete reduction the TiIII complex [meso-(ebthi)Ti(THF)Cl] (3) was also obtained as a by-product of these reactions. By insertion into the Ti-CPh bond carbon dioxide reacted with the titanacyclopropene structure of the alkyne complex [meso-(ebthi)Ti(η2-PhC2SiMe3)] (2a), with untypical regioselectivity to yield the α-silyl-substituted meso-(ebthi)titanafuranone 6a. In the analogous reactions of the complexes [(thi)2Ti(η2-PhC2SiMe3)] (thi = η5-tetrahydroindenyl), [rac-(ebthi)Ti(η2-PhC2SiMe3)], and [Cp*2Ti(η2-PhC2SiMe3)] with carbon dioxide typical regioselectivity (insertion into the M-CSi bond of the titanacyclopropene) was observed, yielding the β-silyl-substituted titanafuranones 7, 8a, and 9. These results show that insertion of carbon dioxide into the M-C bond of the titanacyclopropene structure of the alkynemetallocene complexes is governed by the substitution pattern of the alkyne and the steric enviroment around the metal center. The complexes 3, 6a, and 7 were investigated by X-ray crystal structure analysis.
