Claudia Lefeber

Intramolekulare Cyclisierung von terminal disubstituierten α, ω-Diinen an Titanocen “Cp2Ti” mit einer nachfolgenden, ungewöhnlichen Cp-ringöffnung und neuen intramolekularen CC-Knüpfung

Abstract The reaction of Cp 2 Ti(Me 3 SiC 2 SiMe 3 ) ( 1 ) with terminal disubstituted α,ω-diynes RC≡C(CH 2 ) n C≡CR affords, after substitution of Me 3 SiC 2 SiMe 3 , bicyclic titanacyclopentadienes via intramolecular cyclization. The stability of the obtained products 2, 3 and 5 is determined by the spacer length ( n = 2, 4, 5, 6). The four-membered ring derivatives ( n = 2) 2a and 2b were obtained in good yield. In the case of n = 4 the bicyclic six-membered ring 3 was formed at first, which rearranges to a stable tricyclic η 4 : η 3 -dihydroindenyl-Ti complex 4 by Cp cleavage and intramolecular CC coupling. Complex 4 was characterized by X-ray structure analysis and NMR spectroscopy. An increase of spacer length ( n > 4) provides indefinable secondary and decomposition products.

Regioselektive reaktionen der fremdligandfreien titanocen-alkin-komplexe Cp2Ti(RC2SiMe3) (R = Me3Si,Ph, tBu, nBu)☆

Abstract Depending on different substituents in the reaction of Cp 2 TiCl 2 with magnesium and the alkynylsilanes RC≡CSiMe 3 (R = SiMe 3 , Ph, t Bu, n Bu, n Pr, Me) in tetrahydrofuran, titanacyclopropenes (R = SiMe 3 , Ph, t Bu 1 , n Bu 2 ), symmetrical substituted titanacyclopentadienes (R = Me 5 ) or in a competition reaction both types of complexes (R = n Pr 3 and 4 ) were obtained. The compound Cp 2 Ti( t BuC 2 SiMe 3 ) 1 is the first example of a titanocene complex with an alkyl substituted alkyne without further ligands and was characterized by X-ray crystal structure analysis. The structural and spectroscopical data of 1 were compared with those of other well known complexes of that type, e.g. Cp 2 Ti(Me 3 SiC 2 SiMe 3 ) and Cp 2 Ti(PhC 2 SiMe 3 ) to investigate the influence of different substituents ( t Bu, SiMe 3 , Ph) upon alkyne complexation. The chemo- and regio-selectivities of the obtained alkyne complexes was studied in reactions with alkynes, alcohols, carbon dioxide and acetone. The reaction course depends mostly on steric restrictions, being in the first step kinetically favored at the Si-substituted C-atom of the alkyne and giving β-SiMe 3 -substituted products, which rearrange in some cases into the thermodynamically more stable α-SiMe 3 -substituted products.

THE FIRST CHIRAL EARLY-LATE HETEROBIMETALLIC COMPLEX : A TITANIUM(IV)-PALLADIUM(II) COMPLEX BASED ON SALENOPHOS

Abstract The synthesis of the chiral polyfunctional diphosphine salenophos 1 is described. The new ligand bearing hard and soft coordination sites chelates titanium(IV) as well as palladium(II) in a defined manner provided a certain order during the introduction of the two metals was kept. In this way the first chiral early-late heterobimetallic complex could be synthesized. It was fully characterized by NMR spectroscopy and X-ray structural analysis. Remarkable features of the heterobimetallic complex are the trans coordination of the phosphine groups on palladium and the distance between Ti and Pd which is more than 4.13 A.

Intramolekulare Insertion eines η5-cyclopentadienyl-ringes in einem bis-η5-cyclopentadienyltitanacyclopentadien

Abstract The reaction of in situ-generated titanocene “Cp 2 Ti” with 2 equiv. of alkynes Me 3 SiCCR yields a mixture of symmetrically ( R = Ph ( 3 ), Py ( 6 ) ) and unsymmetrically ( R = Ph ( 4 ) , Py ( 7 ) substituted titanacyclopentadienes. Complex 7 is unstable and rearranges with an intramolecular insertion of one Cp of the titanocene fragment into the unsymmetrically substituted titanacyclopentadiene to produce the dihydroindenyl complex 8 , which was characterized by an X-ray structure analysis.

DARSTELLUNG UND REGIOSELEKTIVE REAKTIONEN DES PHOSPHINFREIEN ZIRCONOCEN-ALKIN-KOMPLEXES CP2ZR(THF)(TBUC2SIME3)

Abstract The reaction of Cp 2 ZrCl 2 with magnesium and t BuC 2 SiMe 3 in tetrahydrofuran yields the first zirconocene complex with an alkyl substituted alkyne without additional phosphine ligands Cp 2 Zr(THF)( t BuC 2 SiMe 3 ) 1 . That complex is stable at room temperature and was characterized by its IR and NMR spectra. The spectroscopical data of 1 were compared with those of the well known complex of that type Cp 2 Zr(THF)(Me 3 SiC 2 SiMe 3 ) 2 to study the influence of different sterical and electronical influences of the substituents ( t Bu and SiMe 3 ) upon alkyne complexation. The chemo- and regio-selectivity of complex 1 was studied in a hydrogen transfer reaction and in reactions with carbon dioxide and acetone. The results show mostly a kinetically favored reaction at the Si-substituted C-atom of the complexed alkyne, giving the β-SiMe 3 -product, which rearranges into the thermodynamically more stable α-SiMe 3 -substituted products. In contrast to titanocene in the case of zirconocene complexes coupling reactions of RC≡CSiMe 3 (R = SiMe 3 , t Bu) could be realized.

The hydrosilylation of ald-and ketimines catalyzed by titanocene complexes

Different titanocene complexes 1–10 were tested in the catalytic hydrosilylation of ald-and ketimines with Ph2SiH2. The highest conversions were obtained with Cp2Ti(PhCCSiMe3) 1 up to 98 % at room temperature.