METAL-BINDING OF POLYALCOHOLS .4. STRUCTURE AND MAGNETISM OF THE HEXANUCLEAR, MU(6)-OXO-CENTERED [OFE6(H-(3)THME)(3)(OCH3)(3)CL-6](2-) (THME=1,1,1-TRIS(HYDROXYMETHYL)ETHANE)

The addition of [N(CH3)(4)]OH to a methanolic solution of FeCl3 and th me (thme = 1,1,l-tris(hydroxymethyl)ethane) yielded [N(CH3)(4)](2)[OFe 6(H(-3)thme)3(OCH3)(3)Cl-6]. 2H(2)O (1) Crystal data: C26H64Cl6Fe6N2O1 5, trigonal space group P31c, a = 12.459(2) Angstrom, c = 18.077(4) An gstrom, Z = 2. The complex anion exhibits the well-known mu(6)-O-Fe-6- (mu(2)-OR)(12) structure with three mu(2)-methoxo bridges, three tripl y deprotonated H(-3)thme ligands, where each alkoxo group bridges two Fe-III centers, and six terminally coordinating Cl- ligands. In contra st to two previously described ferric complexes with an analogous stru cture of the complex core, compound 1 is stable in air. Variable-tempe rature magnetic susceptibility measurements established antiferromagne tic exchange coupling interactions with J(trans)(Fe-mu(6)-O-Fe) = 24.5 cm(-1), J(cis)(Fe-mu(2)-O-thme-Fe) = 11.5 cm(-1), and J(cis)'(Fe-mu(2 )-OCH3-Fe) = 19.5 cm(-1). The unexpectedly high value for J(trans) is explained by means of a superexchange pathway and is discussed for a s implified model by using MO calculations at the extended Huckel level.