Triphenylamine Derivatives with Para-Disposed Pendant Electron-Rich Organoiron Alkynyl Substituents: Defining the Magnetic Interactions in a Trinuclear Iron(III) Trication

The syntheses of two triarylamine derivatives featuring
one and
three electron-rich Fe­(II) “(η2-dppe)­(η5-C5Me5)­FeCC–”
pendant substituents in para position­(s) on the aryl rings (1, 2) is reported, along with those of their
corresponding radical tri- and monocations (13+, 2+). The former
species (13+) constitutes a new
organometallic triradical. The magnetic interactions between the Fe­(III)
units in this novel trication were investigated by NMR and SQUID.
Its ground spin state was shown to be a doublet, with a “mean”
antiferromagnetic coupling constant of J ≈
−14 cm–1 between the unpaired spins, from
consideration of the classic Hamiltonian for a symmetric C3v triradical: H = −2J(Sa·Sb + Sb·Sc + Sc·Sa).