Low-Coordinate Transition-Metal Complexes of a Carbon-Substituted Hemiporphyrazine

The metallation of the core-modified phthalocyanine analogue
dicarbahemiporphyrazine with manganese, iron, and cobalt results
in the formation of low-coordinate metal(II) complexes. All three
compounds are produced by the reaction of metal carbonyls with
the free base macrocycle. As in many other carbaporphyrinoids,
the internal C−H bonds remain intact upon metallation, resulting
in the formation of two long-range agostic-type interactions. Each
metal can thus be considered as a three-coordinate ion, where
two inner isoindolene nitrogens and a single axial pyridine are
bound to the metal. The manganese and cobalt complexes,
Mn(dchp)py and Co(dchp)py, are nearly isostructural, but the iron
complex, Fe(dchpH2)py, exhibits a reduction at an iminic double
bond upon metallation.