Three-Coordinate Iron(II) Dialkenyl Compound with NHC Ligation: Synthesis, Structure, and Reactivity

The
reaction of [(IPr2Me2)2FePh2] with PhCCPh furnished a three-coordinate iron­(II)
dialkenyl complex, [(IPr2Me2)­Fe­(σ-CPhCPh2)2] (1, IPr2Me2 = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene), that represents
a rare example of isolable low-coordinate iron alkenyl complexes with
a high-spin ground state. Complex 1 was characterized
by 1H NMR spectroscopy, solution magnetic susceptibility
measurement, Mössbauer spectroscopy, single-crystal X-ray diffraction
study, and elemental analyses. A reactivity study revealed the reactions
of 1 with PhCH2Cl to produce cross-coupling
product Ph2CCPhCH2Ph (2), with [Cp2Fe]­[BArF4] to yield
Ph2CCPh–CPhCPh2 (3), and with CO, 2,6-dimethylphenyl isocyanide, and phenyl
azide to produce novel iron(0) and iron­(II) complexes 4–6 bearing triphenylvinyl-derived ligands. These
transformations demonstrated the high reactivity of the low-coordinate
iron alkenyl complex.