title: Reactions of 2-Substituted Pyridines with Titanocenes and Zirconocenes: Coupling versus Dearomatisation.
abstract: Reactions of group 4 metallocene sources with 2-substituted pyridines were investigated to evaluate their coordination type between innocent and reductive dearomatisation as well as to probe the possibility for couplings. A dependence on the cyclopentadienyl ligands (Cp, Cp*), the metals (Ti, Zr), and the substrates (2-phenyl-, 2-acetyl-, and 2-iminopyridine) was observed. While 2-phenylpyridine is barely reactive, 2-acetylpyridine reacts vigorously with the Cp-substituted complexes and selectively with their Cp* analogues. With 2-iminopyridine, in all cases selective reactions were observed. In the isolated [Cp2Ti], [Cp2Zr], and [Cp*2Zr] compounds the substrate coordinates by its pyridyl ring and the unsaturated side-chain. Subsequently, the pyridine was dearomatised, which is most pronounced in the [Cp*2Zr] compounds. Using [Cp*2Ti] leads to the unexpected paramagnetic complexes [Cp*2TiIII(N,O-acpy)] and [Cp*2TiIII(N,N'-impy)]. This highlights the non-innocent character of the pyridyl substrates.
authors.affiliation: Leibniz-Institut für Katalyse e.V. an der, Universität Rostock, Albert-Einstein-Strasse 29a, 18059, Rostock, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Reiß
authors.affiliation: Leibniz-Institut für Katalyse e.V. an der, Universität Rostock, Albert-Einstein-Strasse 29a, 18059, Rostock, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Altenburger
authors.affiliation: Leibniz-Institut für Katalyse e.V. an der, Universität Rostock, Albert-Einstein-Strasse 29a, 18059, Rostock, Germany.
authors.forename: Lisanne
authors.initials: L
authors.lastname: Becker
authors.affiliation: Leibniz-Institut für Katalyse e.V. an der, Universität Rostock, Albert-Einstein-Strasse 29a, 18059, Rostock, Germany.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Schubert
authors.affiliation: Leibniz-Institut für Katalyse e.V. an der, Universität Rostock, Albert-Einstein-Strasse 29a, 18059, Rostock, Germany.
authors.forename: Haijun
authors.initials: H
authors.lastname: Jiao
authors.affiliation: Leibniz-Institut für Katalyse e.V. an der, Universität Rostock, Albert-Einstein-Strasse 29a, 18059, Rostock, Germany.
authors.forename: Anke
authors.initials: A
authors.lastname: Spannenberg
authors.affiliation: Leibniz-Institut für Katalyse e.V. an der, Universität Rostock, Albert-Einstein-Strasse 29a, 18059, Rostock, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Hollmann
authors.affiliation: Leibniz-Institut für Katalyse e.V. an der, Universität Rostock, Albert-Einstein-Strasse 29a, 18059, Rostock, Germany.
authors.forename: Perdita
authors.initials: P
authors.lastname: Arndt
authors.affiliation: Leibniz-Institut für Katalyse e.V. an der, Universität Rostock, Albert-Einstein-Strasse 29a, 18059, Rostock, Germany. uwe.rosenthal@catalysis.de.
authors.forename: Uwe
authors.initials: U
authors.lastname: Rosenthal
keywords: dearomatisation; metallacycles; metallocenes; pyridines; reduction