Die Beständigkeit von (η 5-C 5H 4R) 2Ti(CCR′) 2 in Abhängigkeit von den elektronischen Eigenschaften der Cyclopentadienyl-Liganden. Die Festkörperstruktur von (η 5-C 5H 5)(η 5-C 5H 4SiMe 3)Ti(CCSiMe 3) 2

Abstract

The synthesis of the titanocene dichlorides (η 5-C 5H 5)(η 5-C 5H 4SiMe 3)TiCl 2 ( 3) and (η 5-C 5H 4CO 2R) 2TiCl 2 ( 8a, R=CH 3; 8b, R=CH 2CH 3), which contain either electron-donating or electron-withdrawing substituents at the cyclopentadienyl fragments is discussed. While the reaction of 8a or 8b with LiCCR′ in different stoichiometric ratios leads only to product mixtures from which no pure components could be isolated, treatment of 3 with two equivalents of LiCCR′ ( 9a, R′=C 6H 5; 9b, R′= t Bu; 9c, R′=SiMe 3) selectively produces the bis(alkinyl) titanocenes (η 5-C 5H 5)(η 5-C 5H 4SiMe 3)Ti(CCR′) 2 ( 10a, R′=C 6H 5; 10b, R′= t Bu; 10c, R′=SiMe 3). However, it was found that when complex 10c is stirred in tetrahydrofuran solutions, Me 3SiCC is eliminated and Me 3SiCCCCSiMe 3 ( 11) along with [(η 5-C 5H 5)(η 5-C 5H 4SiMe 3)Ti(CCSiMe 3)] 2 ( 12) is formed.The solid-state structure of (η 5-C 5H 5)(η 5-C 5H 4SiMe 3)Ti(CCSiMe 3) 2 ( 10c) is reported. Complex 10c crystallises in the monoclinic space group P c with two independent molecules in the asymmetric unit and with the cell constants a=20.8131(6), b=10.6615(3), c=12.2543(4) Å, β=101.12(3)°, V=2668.14(14) Å 3 and Z=4. 10c exhibits a pseudotetrahedrally coordination sphere around the Ti(IV) centre comprised of the two σ-bonded alkynyl ligands Me 3SiCC and the η 5-coordinated cyclopentadienyl moieties C 5H 5 as well as C 5H 4SiMe 3.