A NEW OXO-CENTERED, MIXED-VALENCE HETEROTRINUCLEAR COMPLEX, MN(III)NI(III)MN(II)O(PHCOO)(6)PY-3 CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES

A new mixed-valence heterotrinuclear complex, Mn(III)Ni(III)Mn(II)O(Ph COO)(6)Py-3, was synthesized using NBu4MnO4 as an oxididant. In the re action, Ni(II) was oxidized to Ni(II) while Mn(VII) was reduced to Mn( II) and Mn(III). Crystals are monoclinic, space group C2/C, with a=58. 93(4), b = 11.784(3), c = 24.883(9) Angstrom, beta = 100.64(4)degrees, V= 16983(13) Angstrom(3), and Dc = 1.35 gcm(-3) for Z = 12. The cryst al structure was solved by direct methods to final R = 0.083, R omega = 0.095. There are two kinds of trinuclear species in the unit cell. O ne is valence delocalized with Ni(2)-O(2) 1.86(2) Angstrom and Mn-O(2) 1.92(1) Angstrom (average value of Mn(II)-O and Mn(III)-O). The other is valence localized with Ni(III)-O(1) 1.84(1) Angstrom, Mn(III)-O(1) 1.88(1) Angstrom and Mn(II)-O(1) 1.97(1)Angstrom. Variable temperatur e (1.5-300K) magnetic susceptibilities indicated an antiferromagnetic exchange interaction among the three metal ions.