Unusual structural types in polynuclear iron chemistry from the use of N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine (edteH4):: Fe5, Fe6, and Fe12 clusters

The syntheses, crystal structures, and magnetochemical characterization of five new iron clusters [Fe5O2(O2CPh)(7)(edte)(H2O)] (1), [Fe6O2(O2CBut)(8)(edteH)(2)] (2), [Fe12O4(OH)(2)(O2CMe)(6)(edte)(4)(H2O)(2)](ClO4)(4) (3), [Fe12O4(OH)(8)(edte)(4)(H2O)(2)](ClO4)(4) (4), and [Fe12O4(OH)(8)(edte)(4)(H2O)(2)](NO3)(4) (5) (edteH(4) = N,N,N,N-tetrakis(2-hydroxyethyl) ethylenediamine) are reported. The reaction of edteH(4) with [Fe3O(O2CPh)(6)(H2O)(3)](NO3) and [Fe3O(O2CBut](6)(H2O)(3)](OH) gave 1 and 2, respectively. Complex 3 was obtained from the reaction of edteH(4) and NaO2CMe with Fe(ClO4)(3), whereas 4 and 5 were obtained from the reaction of edteH(4) with Fe(ClO4)(3) and Fe(NO3)(3), respectively. The core of 1 consists of a [Fe-4(mu(3)-O)(2)](8+) butterfly unit to which is attached a fifth Fe atom by four bridging 0 atoms. The core of 2 consists of two triangular [Fe-3(mu(3)-O)](7+) units linked together by six bridging 0 atoms. Finally, the cores of 3-5 consist of an [Fe-12(mu(4)-O)(4)(mu-OH)(2)](26+) U nit. Variable-temperature (T) and -field (H) solid-state direct and alternating current magnetization (M) studies were carried out on complexes 1-3 in the 1.8-300 K range. Analysis of the obtained data revealed that 1, 2, and 3-5 possess an S = 5/2, 5, and 0 ground-state spin, respectively. The fitting of the obtained M/N mu(B) vs H/T data was carried out by matrix diagonalization, and this gave values for the axial zero-field splitting (ZFS) parameter D of -0.50 cm(-1) for 1 and -0.28 cm(-1) for 2.