[Mn-2(bipym)(H2O)(8)](4+) and [Fe(bipy)(CN)(4)](-) as building blocks in designing novel bipym- and cyanide-bridged heterobimetallic complexes (bipym=2,2 '-bipyrimidine and bipy=2,2 '-bipyridine)

摘要

Two new cyano complexes, K[Fe(bipy)(CN)(4)].H2O (1) and (mu-bipym)[Mn(H2O)(3){Fe(bipy)(CN)(4)}](2)[Fe(bipy)(CN)(4)](2).12H(2)O (2), have been synthesised and their structures determined by single-crystal X-ray diffraction. Complex 1 is made up of mononuclear [Fe(bipy)(CN)(4)](-) anions, potassium cations and water molecules of crystallization. The iron(III) is six-coordinated, being surrounded by two nitrogen atoms of a chelating bipy and four carbon atoms of four cyanide groups [Fe-N and Fe-C 1.991(3)-1.990(3) and 1.958(5)-1.914(5) Angstrom, respectively]. Complex 2 consists of centrosymmetric tetranuclear (mu-bipym)[Fe(H2O)(3){Fe(bipy)(CN)(4)}](2)(2+) cations, [Fe(bipy)(CN)(4)](-) anions and water molecules of crystallization. The cyano-containing iron(III) complex of 1 is present in 2 but in the latter it acts not only as a counterion but also as a monodentate ligand towards the manganese atom through one of its four cyanide groups. Bond lengths and angles around the iron atoms in 2 are practically identical to those observed in 1. The manganese atom in 2 is six-coordinated with two bipym- and one cyanide-nitrogen atoms and three mer-water molecules comprising a distorted octahedral environment [Mn-N(bipym) 2.35(1) and 2.29(1) Angstrom, Mn-N( cyanide) 2.19(2) and Mn-O 2.21(1)-2.12(2) Angstrom]. The manganese-manganese and manganese-iron separations across the bis-chelating bipym and single-cyano bridge are 6.131(6) and 5.092(4) Angstrom, respectively. Studies of the magnetic behaviour of 1 and 2 in the temperature range 1.9-300 K reveal that compound 1 is a magnetically isolated low-spin iron(III) complex with an important orbital contribution whereas significant antiferromagnetic interactions occur in 2 between the manganese(II) ions across bis-chelating bipym (J = -1.2 cm(-1)) and between the manganese(II) and iron(III) ions through the single-cyano bridge (j = -3.0 cm(-1)). The use of [Fe-III(AA)(CN)(4)](-) (AA = bidentate ligand) as a ligand towards metal ions appears very promising in designing new cyano-bridged polynuclear compounds. [References: 36]