A Novel Dimanganese(III) Complex with a Single Hydroxo Bridge. The Synthesis, Structure and Magnetic Susceptibility of Hydroxobis(octaethylporpinato)manganese(III) Perchlorate and a Monomeric Precursor Aquo(octaethylporphinato)manganese(III) Perchlorate.

B. CHENG; F. D. CUKIERNIK; P. FRIES; J. C. MARCHON; W. R. SCHEIDT

INORGANIC CHEMISTRY

American Chemical Society

Año: 1995 vol. 34 p. 4627 - 4639

0020-1669

The synthesis and structural and magnetic characterization of a dimanganese(II1) complex with a novel, single, hydroxo bridge is described. The complex, (u-hydroxo)bis((octaethylporphinato)manganese(III)) perchlorate, can be prepared by protonation of an oxo-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(0H)}Cl04 are bridged by a single hydroxo ligand with an average Mn-0 distance of 2.011 A and a Mn-O(H)-Mn bridgeangle of 152.73'. The average Mn-N, distance is 2.006 A. The two porphyrin rings are crowded against each other and are hence canted with a dihedral angle of 12.7'. An additional distortion from ring crowding occurs in the coordination angles 0-Mn-N, at one manganese(II1) ion but not at the other. The magnetic susceptibilityof the hydroxo-bridged complex has been measured over the temperature range 2-300 K. The observed behavior is typical of an exchangelcoupled binuclear complex. The data have been fit to the total spin Hamiltonian    (zo = %l)    +  %2) - 2JSlS2) of a zero-field-split, high-spin d4-d4 dimer in its actual crystallographic geometry, using numerical techniques. The hydroxide bridge supports a relatively strong antiferromagnetic coupling (2J =-71.0 f 0.4 cm-I) between two zero-field-split (D = -8 f 2 cm-I) manganese(II1) ions. The synthesis and characterization of one monomeric precursor, [Mn(OEP)(H20)]C104*H20,is also reported. This species is a simple paramagnet. The crystal structure analysis shows it to be a five-coordinate, high-spin manganese(II1)complex. Crystal data: {[Mn(OEP)]2(OH)}ClO4*3CH2Cl2,= 14.791(4) A, b = 14.895(2) A, c = 18.634(4) A, a = 69.79(2)', p = 89.24(2)', y = 88.86(2)', triclinic, space group Pi,V = 3851.7(14) A3, 2 = 2, R I = 0.0655 for 15 643 observed data based on F, I4.0a(F0), WRZ= 0.1631 for 19 422 total unique data, least-squares refinement on      using all data; [Mn(OEP)(H20)]ClO4.H20, a = 12.800(1) A, b = 13.506(4) A, c = 13.355(7) A, a = 64.80 (2)', p = 62.36(3)", y = 85.67(3)", triclinic, space group Pi, V = 1829.1(11) A3, 2 = 2, R I = 0.0754 for 5715 observed data based on F, 2 4.0a(F0), wR2 = 0.2210 for 8891 total unique data, least-squares refinement on      using all data.