- Synthesis, crystal structures and some properties of dimethylsilylene-bridged ansa-permethyltitanocene [Ti(IV), (III) and (II)] complexes
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Dimethylsilylene-bridged complexes Me2Si(C5Me4)2TiCl (2), Me2Si(C5Me4)2Ti[η2-C2(SiMe3)2] (3) and Me2Si(C5H4)2Ti[η2-C2(SiMe3)2] (4) have been prepared by the general methods which are known for obtaining of analogous non-bridged titanocene complexes. X-ray crystal structures of Me2Si(C5Me4)2TiCl2 (1), 2, and 3 reveal that the dihedral angle ? between the least-squares planes of cyclopentadienyl rings increases in the order 2 5HMe4)2Ti and (C5Me5)2Ti compounds shows that the value of ? increases in the series (C5Me5)2Ti 5HMe4)2Ti 2Si(C5Me4)2Ti, e.g. in the bis(trimethylsilyl)acetylene complexes from 41.1° for (C5Me5)2Ti[η2-C2(SiMe3)2] (9) to 50.0° for (C5HMe4)2Ti[η2-C2(SiMe3)2] (8) and to 53.5° for 3. Compounds 3, 8 and 9 induce the head-to-tail dimerization of 1-hexyne with the selectivity of 72percent, 21percent and ca. 100percent respectively. The discrepancy between the selectivities and the values of ? for 3 and 8 is accounted for by a larger flexibility of the titanocene skeleton in 8, affording a larger space for a non-specific coordination of 1-hexyne. The effects of the μ-Me2Si group in 2 and 3 on some of their properties are compared with the effects of Me and H substituents in the non-ansa compounds with controversial results. For instance, the affinity of 2 to 2-methyltetrahydrofuran approaches that of (C5H2Me3)2TiCl whereas the shift of the v(C≡C) vibration in 3 indicates a stronger metal-acetylene bond than in 9.
- Varga, Vojtech,Hiller, Jo?rg,Gyepes, Ro?bert,Pola?s?ek, Miroslav,Sedmera, Petr,Thewalt, Ulf,Mach, Karel
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- Metal Complexes with Bridged Permethylated Cyclopentadienyl Ligands
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The preparation of the permethylated silyl-bridged dicyclopentadienyl ligands Me2Si(Me4C5H)2 (1) and C2H4(Me2Si(Me4C5H))2 (2) is reported.Reaction of dimetalated 1 with TiCl4 and ZrCl4 yielded the corresponding metallocenophane dihalides 3 and 4, while treatment of the dilithio derivative of 2 with GeCl2 * dioxane, SnCl2, and FeCl2 yielded the bridged metallocenes 5, 6, and 7.
- Jutzi, Peter,Dickbreder, Reiner
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p. 1750 - 1754
(2007/10/02)
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