Oxalate and 2,2′-bipyrimidine as bis-chelating ligands in the honeycomb layered compound {[Fe2(bpym)(ox)2]·5H2O}n

Abstract

The novel two-dimensional iron(II) compound of formula {[Fe₂(bpym)(ox)₂]·5H₂O}_n (1) [bpym = 2,2′-bipyrimidine and ox = oxalate dianion] is obtained by reaction of oxalic acid, iron(II) chloride and 2,2′-bipyrimidine in aqueous solution. The structure of 1 is made up of oxalato-bridged iron(II) chains cross-linked by bischelating bpym affording a honeycomb lattice. Variable-temperature magnetic susceptibility data of 1 show the occurrence of relatively large antiferromagnetic interactions between the high spin iron(II) ions separated by more than 5.5 Å through bridging bpym [J_bpym = −4.0(2) cm⁻¹] and ox [J_ox = ca. −7.8(2) cm⁻¹] ligands. These values compare well with those obtained in the iron(II) chain [Fe(dpa)(ox)]_n (2) [J_ox = −8.0(2) cm⁻¹] (dpa = 2,2′-dipyridylamine) and dinuclear {[Fe(H₂O)₄]₂(bpym)}(SO₄)₂·2H₂O (3) (J_bpym = −3.4 cm⁻¹) compounds where bischelating ox (1 and 2) and bpym (1 and 3) groups and the bidentate dpa (2) ligand are present.