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1)Dass diese aus dem Chloracettoluid iihnlioh zusammengesetzten, vielleicht isomeren Substanzen bestehen, ergiebt sich aus den mit nicht ganz reinen Praparaten ausgefchrten Chlorbestimmungen.2) Diese Berichte XXIV, 2588.

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The halfsandwich complexes [(η 5 -C 9 H 7 )TiCl 3 ] (3a), [(η 5 -Me 3 Si-1-C 9 H 6 )TiCl 3 ] (3b), [(η 5 -Me-1-C 9 H 6 )TiCl 3 ] (3c), [(η 5 -Me 2 -4,7-C 9 H 5 )TiCl 3 ] (3d), [(η 5 -Me 3 Si-2-C 9 H 6 )TiCl 3 ] (3e), [(η 5 -Me 2 Ϫ1,3-C 9 H 5 )TiCl 3 ] (3f), [(η 5 -(CH 2 ) 3 Ϫ5,6-C 9 H 5 )TiCl 3 ] (4), and [(η 5 -(CH 2 ) 3 Ϫ1,7-C 9 H 5 )TiCl 3 ] (5) are accessible by reacting the in position 1 or 3 Me 3 Si-functionalized appropriate indenes with TiCl 4 . CG-TiCl 2 compounds (CG ϭ Constraint Geometry) can be synthesized by the subsequent reaction of Br-2-C 9 H 7 (6a), Br-2-Me 2 -1,3-C 9 H 5 (6b) and Br-2-(CH 2 ) 3 -5,6-C 9 H 5 (6c), respectively, with magnesium in presence of Me 2 SiCl 2 to give the respective Me 2 SiCl-functionalized indenes which further react with an excess of H 2 N t Bu to afford t BuHN-SiMe 2 -2-C 9 H 7 (8a), t BuHN-2-Me 2 -1,3-C 9 H 5 (8b) and t BuHNϪ2-(CH 2 ) 3 -5,6-C 9 H 5 (8c). The latter species produce on their consecutive reaction with n BuLi, [TiCl 3 ·3Thf] and PbCl 2 the titanium CG-complexes [(η 5 -SiMe 2 N t Bu-2-C 9 H 6 )TiCl 2 ] (9a), [(η 5 -Me 2 -1,3-SiMe 2 N t Bu-2-C 9 H 4 )TiCl 2 ] (9b), and [(η 5 -Me 2 SiN t Bu-2-(CH 2 ) 3 -5,6-C 9 H 4 )TiCl 2 ] (10). The same synthe- Chem. 2007, 633, 2242Ϫ2254 sis protocol allows the preparation of [(η 5 -Me 2 SiN t Bu-1-Me 3 Si-2-C 9 H 5 )TiCl 2 ] (12) a CG complex in which the Me 2 SiN t Bu unit is located in position 1. The polymerization of ethene by using 3Ϫ5 and 9Ϫ12 and MAO (MAO ϭ methylaluminoxane) as cocatalyst is described to show if a strong activity correlation between 3Ϫ5 and 9Ϫ12 exists. In order to optimize the catalytic activity of 3Ϫ5 the electronic (cyclic voltammetry, UV-Vis spectroscopy) and steric properties (Multiple Overlap Solid Angle) of these species were analyzed. Based on the obtained data, semi-empirical structure-activity models for 3Ϫ5 are proposed to obtain an optimized substituent pattern for the indenyl moiety. Substituents in position 1 or 4 of the appropriate indenyl π-perimeters show a strong bathochromic (ϩM) and electro-neutral to electro-negativ effect (0/-I).

Me3Si-substituted indenes of type 1-SiMe3-3,4-(CH2)3C9H5 (9), 1-SiMe3-4-R-7-R′C9H5 (11a, R = R′ = Me; 11b, R = R′ = Ph; 11c, R = Me, R′′ = Ph) and 1,1′ -(SiMe3)2-4,7-Me2C9H4 (12) were synthesised as precursors for piano-stool type halfsandwich indenyl-titanium trichloride complexes.Treatment of 9, 11, and 12 with equimolar amounts of TiCl4 gives the complexes (η5-3,4-(CH2)3C9H5)TiCl3 (13), (η5-4-R-7-R′C9H5)TiCl3 (14a, R =R′ = Me; 14b, R =R′= Ph; 14c, R = Me, R′ = Ph), and (η5-1-SiMe3-4,7-Me2C9H4)TiCl3 (15), respectively, with liberation of Me3SiCl.Detailed UV/vis spectroscopic and cyclic voltammetric studies were carried out which allow a comparison of substituent effects in 13 - 15.