Alkyne coupling reactions mediated by iron(II) complexes:: Highly chemo- and regioselective formation of η6-coordinated arene and pyridine complexes

Reaction of the bis(acetonitrile) complex 1 with HCequivalent toCPh affords the (allyl)carbene complex 3, which results from a head-to-tail coupling of two alkynes. The tris(acetonitrile) complex [Fe(C5Me5)(CH3CN)(3)][PF6] (2) mediates highly chemo- and regioselectiue [2 + 2 + 2] cycloaddition reactions of Cequivalent toC and Cequivalent toN triple bonds, providing access to pi-arene and -pyridine complexes. The pyridine complex 5a has been characterized by an X-ray crystal structure.