Synthesis of 1-Azatriene Complexes of Tungsten: Metal-Promoted Ring-Opening of Dihydropyridine.

ABSTRACT

For nearly a century, chemists have explored how transition-metal complexes can affect the physical and chemical properties of linear conjugated polyenes and heteropolyenes. While much has been written about higher hapticity complexes (η4-η6), less is known about the chemistry of their η2 analogues. Herein, we describe a general method for synthesizing 5,6-η2-(1-azatriene) tungsten complexes via a 6π-azaelectrocyclic dihydropyridine ring-opening that is promoted by the π-basic nature of {WTp(NO)(PMe3)}. This study includes detailed spectroscopic and crystallographic data for the η2-dihydropyridine and η2-1-azatriene complexes, both of which were prepared as single regio- and stereoisomers.