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Reactions of 2‐Substituted Pyridines with Titanocenes and Zirconocenes: Coupling versus Dearomatisation
Author(s) -
Reiß Fabian,
Altenburger Kai,
Becker Lisanne,
Schubert Kathleen,
Jiao Haijun,
Spannenberg Anke,
Hollmann Dirk,
Arndt Perdita,
Rosenthal Uwe
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201504411
Subject(s) - cyclopentadienyl complex , chemistry , metallocene , paramagnetism , ring (chemistry) , pyridine , medicinal chemistry , substrate (aquarium) , stereochemistry , catalysis , crystallography , organic chemistry , polymerization , quantum mechanics , physics , oceanography , geology , polymer
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 [Cp 2 Ti], [Cp 2 Zr], and [Cp* 2 Zr] 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* 2 Zr] compounds. Using [Cp* 2 Ti] leads to the unexpected paramagnetic complexes [Cp* 2 Ti III ( N,O ‐acpy)] and [Cp* 2 Ti III ( N , N ′‐impy)]. This highlights the non‐innocent character of the pyridyl substrates.