Synthesis, crystal structure and magnetic properties of the manganese(II) chains [Mn(bipym)(NO3)2] and [Mn(bipym)(NCO)2],

Two new manganese(II) chains of formula [Mn(bipym)(NO3)2] 1 and [Mn(bipym)(NCO)2] 2 (bipym = 2,29- bipyrimidine) have been synthesized and their structures determined by single-crystal X-ray diffraction. Their structures consist of zigzag chains of bipym-bridged manganese(II) ions where electroneutrality is achieved by monodentate and chelating nitrate groups (1) and by N-bonded terminal cyanate ligands (2). The manganese atom in 1 is seven-co-ordinated being surrounded by four bipym nitrogens and three nitrato-oxygens [Mn]N and Mn]O 2.362(2)-2.330(2) and 2.205(2)-2.392(2) Å, respectively]. The manganese atom in 2 is six-co-ordinated with four bipym- and two cyanato-nitrogen atoms in cis position comprising a distorted-octahedral environment [average Mn]N (cyanato) and Mn]N (bipym) bond distances 2.097(3) and 2.355(3) Å, respectively]. In both structures the bipym group acts as a bis(bidentate) ligand forming two five-membered chelate rings, the values of the bite angle at the bipym being 69.5(1) and 69.3(1)8 in 1 and 69.5(1)8 in 2. The intrachain metal-metal separations are 6.239(1) and 6.247(1) Å in 1 and 6.234(1) Å in 2. Variable-temperature magnetic susceptibility data in the temperature range 290-4.2 K show the occurrence of a significant intrachain antiferromagnetic coupling between the local high-spin manganese(II) ions, the values of the exchange coupling parameter J being 20.93 (1) and 21.1 (2) cm21. The efficiency of bis(chelating) ligands such as bipym and oxalate in mediating antiferromagnetic coupling between manganese(II) ions is analysed and discussed in the light of available magnetostructural data.