Iron and Palladium Complexes of Pacman Phosphanes

Pacman phosphanes, which can be regarded as multidentate
macrocyclic
ligands with two P-donor centers, were used for the synthesis of palladium
and iron complexes. The isolation and complete characterization of
Pd(0)-, Pd(II)-, and Fe(II)-Pacman phosphane complexes were achieved.
While the Pd complexes formed both mononuclear and binuclear distorted
planar complexes, distorted octahedral environments were observed
in the iron complexes. Depending on the substituent on the phosphorus
atoms, either a diamagnetic low spin iron(II) complex or a paramagnetic
high spin iron(II) complex was found. The electrochemical investigations
of the iron(II) complexes showed three redox events, with the first
being both electrochemically and chemically reversible. The structure
and bonding of all Pacman phosphane complexes is discussed on the
basis of single-crystal X-ray studies and quantum chemical computations.