SYNTHESIS, CHEMICAL-PHYSICAL CHARACTERIZATION, AND REDOX PROPERTIES OF A NEW MIXED-LIGAND HETEROBIMETALLIC N-BRIDGED DIMER - RAPHENYLPORPHYRINATO)MANGANESE)((PHTHALOCYANINATO) IRON)]

A new mixed-ligand heterobimetallic mu-nitrido bridged complex of the formula (TPP)Mn-N-Fe(Pc) (I) has been prepared from (TPP)MnN3 and (Pc) Fe (TPP = tetraphenylporphyrinato anion, Pc = phthalocyaninato anion) and its molecular and electronic structure were investigated by EPR, I R, Raman, UV-visible and Mossbauer spectroscopy as well as by electroc hemistry and magnetic susceptibility measurements. The complex, formal ly a mixed-valence Mn-Fe d(8) system, is low-spin (diamagnetic). Mossb auer data indicate an unbalanced positive charge distribution for the two metal centers and an approach to the formally mixed-valence specie s (TPP)Mn-IV=N -Fe-III(Pc). This assignment differs from findings for the related complex (TPP)Fe-III1/2-N- Fe-III1/2(Pc) (II) and other sim ilar N-bridged analogues, including (TPP)Fe-IV=N-Ru-III(Pc). A metal c entered one-electron oxidation occurs by reaction of I with dilute HCl O4 and leads to formation of a Mn(IV)=N-Fe(IV) species, I-ClO4. Pyridi ne can coordinate with I to give a mono(pyridine) adduct and the forma tion constant for this reaction has been determined spectrophotometric ally in CH2Cl2 solutions. The singly oxidized complex, I-ClO4, also re acts with pyridine and is converted to a bis-pyridine derivative conta ining the fragment [(py)(TPP)Mn-N-Fe(Pc)(py)](+). Complex I can underg o five reversible one-electron oxidations in CH2Cl2 and up to six elec trons can be extracted from the neutral complex in pyridine. Both sets of reactions were characterized by cyclic voltammetry which was used to determine the half-wave potentials for each electrode reaction and also to evaluate formation constants for pyridine binding to the neutr al and singly oxidized forms of the complex.