STRUCTURE AND REACTIONS OF AN 8-COORDINATE MN(II) COMPLEX - [MN(TMPA)2](CLO4)2 (TMPA = TRIS[(2-PYRIDYL)METHYL]AMINE)

The synthesis, structure and reaction products of an eight-coordinate Mn(II) complex are described. Tbe reaction of Mn(ClO4)2 . 6H2O with tb e tripodal amine ligand tris(2-methylpyridyl)amine (TMPA) yields the e ight-coordinate complex [Mn(TMPA)2](ClO4)2 (1) which crystallizes in t he monoclinic space group P2(1)/n with a=9.7063(3), b=10.929(3), c = 1 8.378(7) angstrom, beta=101.96(3)-degrees. The X-ray structure shows a n eight-coordinate Mn(II) ion with coordination to six pyridyl and two amine nitrogens which form a bicapped trigonal antiprism geometry. Th e oxidation of the Mn(II) complex with H2O2 produces the dioxo-bridged dimeric Mn(III,IV) complex [Mn2(mu-O)2(TMPA)2](ClO4)3 which shows ant iferromagnetic coupling between the two valence trapped Mn ions leadin g to S=1/2 ground state in a 16-line EPR spectrum typical of such diox o-bridged mixed valent Mn complexes and similar to the EPR spectrum ex hibited by the S2 State Photosystem II. While the Mn(II) complex is st able to oxidation by O2, in the presence of catechol in methanol solut ion, it is readily oxidized by O2 to give the catecholate complex. The oxidation of 3,5-di-t-butylcatechol to the quinone by O2 is catalyzed by 1.