Synthesis of a cyano-bridged Fe2Mn linear unit and a Fe2Mn2 square unit by using the [fac-Fe{HB(pz)3}(CN)3]- building block

Mononuclear (LH2)[Fe{HB(pz)(3)}(CN)(3)](2)(.)2H(2)O(.)2MeOH (2) (L = C-meso-3,14-dimethyl-2,6,13,17-tetraazatricyclo[16.4.0.0(7,12)] docosane) and two cyano-bridged bimetallic complexes [{Fe{HB(pz)(3)}(CN)(3)}(2)Mn(MeOH)(4)](.)2MeOH (3) and [Mn2Fe2{HB(pz)(3)}(2) (CN)(6)(4,4'-bipyridine)(2)](ClO4)(2)(.)4MeCN (4) have been prepared and their structures and magnetic properties studied. A crystal structure analysis of complex 2 revealed a hydrogen bonded dimeric structure of two [Fe{HB(pz)(3)}(CN)(3)](-) anions and two water molecules. The structure of 3 consists of a neutral Fe-III-Mn-II-Fe-III molecule and two crystal methanol molecules. The manganese ion is coordinated by two [Fe{HB(pz)(3)}(CN)(3)](-) moieties through cyanide bridging ligands with trans geometry, resulting in a linear trinuclear structure. Reaction of the 2,2'-bipyridine ligand with complex 3 resulted in the formation of complex 4. The crystal structure of 4 consists of a discrete tetranuclear square Fe2Mn2 complex, two perchlorate anions and four acetonitrile solvent molecules. The manganese ions are surrounded by two 2.2'-bipyridine ligands and bridged by two [Fe(tbp)(CN)(3)](-) moieties through cyanide bridging ligands to form a cyclic tetranuclear structure. The magnetic properties of 3 and 4 are found to be dominated by a weak antiferromagnetic interaction of low-spin Fe-III (S = 1/2) and high-spin M-II (S = 5/2). The Fe-III-Mn-II coupling constant J was determined to be -5.90(9) or -7.6(2) cm(-1) for 3 and -2.29(3) cm(-1) for 4. (C) 2004 Elsevier Ltd. All rights reserved.