1-Metalla-1,3,5-hexatrienes and Related Compounds

The term 1-metalla-1,3,5-hexatriene applies to a huge number of transition metal carbene complexes which contain a 1,3-butadien-1-yl side chain attached to the carbene carbon atom. Compounds of this type were found to play a crucial role as key intermediates and have also been utilized as stoichiometric reagents in a number of high-yielding transformations, which may successfully be applied to organic syntheses. Typical reaction pathways, structural features, and preparations of such compounds (with focus on M = Cr and W) have been summarized.