A novel cyano-bridged pentanuclear complex: [{Mn 3(MAC) 3(H 2O) 2}{Fe(CN) 6} 2]·6H 2O·2CH 3OH—synthesis, crystal structure and magnetic properties (MAC=pentaaza macrocyclic ligand)

Abstract

The reaction between K 3[Fe(CN) 6] and [Mn(MAC)(H 2O) 2]Cl 2·4H 2O (MAC=2,13-dimethyl-3,6,9,12,18-pentaazabicyclo-[12.3.1]octadeca-1(18),2,12,14,16-pentaene) in a water/methanol mixture affords a pentanuclear complex with the formula [{Mn 3(MAC) 3(H 2O) 2}{Fe(CN) 6} 2]·6H 2O·2CH 3OH ( 1), whose crystal structure has been solved. It consists of discrete [Mn IIFe IIIMn IIFe IIIMn II] entities. The three {Mn(MAC} 2+ moieties are connected by two [Fe(CN) 6] 3− anions, each one involving two cis cyano bridging groups. The manganese ions display a distorted pentagonal–bipyramidal geometry, with the macrocyclic ligand forming the equatorial plane. The axial positions are occupied by two nitrogen atoms arising from the cyano bridges, for the central manganese atom, and by one aqua ligand and one nitrogen atom from the cyano bridge, for the terminal manganese atoms. The cryomagnetic properties of 1 have been investigated and reveal a new case of irregular spin-state structure.