title: Reactions of group 4 metallocenes with monosubstituted acetonitriles: keteniminate formation versus C-C coupling.
abstract: The reactions of the Group 4 metallocene dichlorides [Cp'2 MCl2 ] (1 a: M=Ti, Cp'=Cp*=η(5) -pentamethylcyclopentadienyl, 1 b: M=Zr, Cp'=Cp=η(5) -cyclopentadienyl) with lithiated MesCH2-C≡N gave [Cp*2 TiCl(N=C=C(HMes))] (3; Mes=mesityl) in the case of 1 a. For compound 1 b, a nitrile-nitrile coupling resulted in a five-membered bridge in 4. The reaction of the metallocene alkyne complex [Cp*2 Zr(η(2) -Me3 SiC2 SiMe3 )] (2) with PhCH2 C≡N led in the first step to the unstable product [Cp*2 Zr(η(2) -Me3 SiC2 SiMe3 )(NC=CH2 Ph)] (5). After the elimination of the alkyne, a mixture of products was formed. By variation of the solvent and the reaction temperature, three compounds were isolated: a diazadiene complex 6, a bis(keteniminate) complex 7, and 8 with a keteniminate ligand and a five-membered metallacycle. Subsequent variation of the Cp ligand and the metal center by using [Cp2 Zr] and [Cp*2 Ti] with Me3 SiC2 SiMe3 in the reactions with PhCH2-C≡N gave complex mixtures.
authors: Leibniz-Institut für Katalyse e.V. an der Universität Rostock, Albert-Einstein-Strasse 29a, 18059 Rostock (Germany), Fax: (+49) 381-1281-51176.
authors: Lisanne
authors: L
authors: Becker
authors: Martin
authors: M
authors: Haehnel
authors: Anke
authors: A
authors: Spannenberg
authors: Perdita
authors: P
authors: Arndt
authors: Uwe
authors: U
authors: Rosenthal
keywords: CC coupling; H shift; deprotonation; metallacycles; metallocenes