Isolation, Purification, and Characterization of High-Valent Complexes from a Manganese Porphyrin Based Catalytic Hydrocarbon Activation System. Crystal and Molecular Structure of μ-Oxo-bis

Article abstract of DOI:10.1021/ja00378a032

High-valent complexes have been isolated from the reactions of (tetraphenylporphinato)manganese(III) derivatives, XMn^IIITPP, with iodosylbenzene in hydrocarbon or halocarbon solvents.When X=N3^- or OCN^-, dimeric μ-oxo-manganese(IV) porphyrin complexes, IVTPP>2)O, 4, are isolated.The dimer IVTPP>2O has been characterized by X-ray crystallography.Intense broad absorption bands near 800 cm^-1 in the infrared spectra of the complexes have been assigned to Mn-O-Mn bands based on 18O substitution.Magnetic susceptibility measurements give μ_eff=2.0 μ_B for IVTPP>2O.The complexes are EPR silent. IVTPP>2O crystallizes as a chlorobenzene solvate in space group Pbcn.The unit cell has a=21.208 (5) Angstroem, b=16.826 (4) Angstroem, and c=22.620 (3) Angstroem and contains four molecules.The structure was solved by the heavy-atom method and converged with a final R=0.094.The IVTPP>2O molecule possesses rigorous crystallographic C₂ symmetry with both Mn atoms, the bridging oxo oxygen atom, and the ligating nitrogen atoms of each N3 ligand lying on the twofold axis.The two Mn atoms are displaced from the mean N4 planes toward the bridging oxygen by 0.10 and 0.08 Angstroem.The average Mn-N(porphyrin) bond distance is 2.014 (19) Angstroem.Two antiferromagnetically coupled d³ Mn(IV) atoms is the best description of the ground state for the dimeric complexes, 4.On the basis of the similarity of the properties observed for both solid-state and solution samples of the complexes, their structures are probably the same in solution as in the solid state.