The synthesis and structural and magnetic characterization of a dimanganese(III) complex with a novel, single, hydroxo bridge is described. The complex, (mu-hydroxo)bis((octaethylporphinato)manganese(III)) perchlorate, can be prepared by protonation of an ore-bridged manganese complex or, more reliably, by hydrolysis of monomeric manganese(III) octaethylporphyrinates. The crystal and molecular structure has been solved using X-ray diffraction data collected with an area detector. The two five-coordinate manganese(III) ions in {[Mn(OEP)](2)(OH)}ClO4 are bridged by a single hydroxo ligand with an average Mn-O distance of 2.011 Angstrom and a Mn-O(H)-Mn bridge angle of 152.73 degrees. The average Mn-N-p distance is 2.006 Angstrom. The two porphyrin rings are crowded against each other and are hence canted with a dihedral angle of 12.7 degrees. An additional distortion from ring crowding occurs in the coordination angles O-Mn-N-p at one manganese(III) ion but not at the other. The magnetic susceptibility of the hydroxo-bridged complex has been measured over the temperature range 2-300 K. The observed behavior is typical of an exchange-coupled binuclear complex. The data have been fit to the total spin Hamiltonian (H-tot = H(1) + H(2) - 2J (S) over right arrow(1) .(S) over right arrow(2)) of a zero-field-split, high-spin d(4)-d(4) dimer in its actual crystallographic geometry, using numerical techniques. The hydroxide bridge supports a relatively strong antiferromagnetic coupling (2J = -71.0 +/- 0.4 cm(-1)) between two zero-field-split (D = -8 +/- 2 cm(-1)) manganese(III) ions. The synthesis and characterization of one monomeric precursor, [Mn(OEP)(H2O)]ClO4 . H2O, is also reported. This species is a simple paramagnet. The crystal structure analysis shows it to be a five-coordinate, high-spin manganese(III) complex. Crystal data: {[Mn(OEP)](2)(OH)}ClO4 . 3CH(2)Cl(2), a = 14.791(4) Angstrom, b = 14.895(2) Angstrom, c = 18.634(4) Angstrom, alpha = 69.79(2)degrees, beta = 89.24(2)degrees, gamma = 88.86(2)degrees, triclinic, space group <P(1)over bar>, V = 3851.7(14) Angstrom(3), Z = 2, R(1) = 0.0655 for 15 643 observed data based on F-o greater than or equal to 4.0 sigma(F-o), wR(2) = 0.1631 for 19 422 total unique data, least-squares refinement on F-2 using all data; [Mn(OEP)(H2O)]ClO4 . H2O, a = 12.800(1) Angstrom, b = 13.506(4) Angstrom, c = 13.355(7) Angstrom, alpha = 64.80 (2)degrees, beta = 62.36(3)degrees, gamma = 85.67(3)degrees, triclinic, space group <P(1)over bar>, V = 1829.1(11) Angstrom(3), Z = 2, R(1) = 0.0754 for 5715 observed data based on F-o greater than or equal to 4.0 sigma(F-o), wR(2) = 0.2210 for 8891 total unique data, least-squares refinement on F-2 using all data.
