Synthesis of a cyano-bridged Fe 2Mn linear unit and a Fe 2Mn 2 square unit by using the [ fac-Fe{HB(pz) 3}(CN) 3] − building block

Abstract

Mononuclear (LH 2)[Fe{HB(pz) 3}(CN) 3] 2 · 2H 2O · 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} 2Mn(MeOH) 4] · 2MeOH ( 3) and [Mn 2Fe 2{HB(pz) 3} 2(CN) 6(4,4 ′-bipyridine) 2](ClO 4) 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 Fe 2Mn 2 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 Mn 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.