Discrete dinuclear complexes and two-dimensional architectures from bridging polynitrile and bipyrimidine (bpym) ligands: Syntheses, structures and magnetic properties of [M2(bpym)(dcne)4(H2O)2 (M=MnII, CoII) and [M 2(bpym)(dcne)4(H2O)4]· 2H2O (M = FeII, CuII) (dcne-=[(CN)2CC(O)OEt)]-)
Abstract
One-pot reactions in aqueous solutions of the polynitrile anion dcne - (2,2-dicyano-1-ethoxyethenolate = [(CN)2-CC(O)OEt)] -] with the MII ions (M = Mn, Fe, Co, Cu) in the presence of bpym (2,2′-bipyrimidine) afford the first mixed dcne/bpym compounds [M2(bpym)(dcne)4(H2O)2] (1: M = Mn; 2: M = Co) and [M2(bpym)(dcne)4(H2O) 4]·2H2O (3: M = Fe; 4: M = Cu). The new compounds have been characterized by IR spectroscopy and X-ray crystallography. Compounds 1 and 2 are isostructural, with each metal ion being located in an MN 5O pseudo-octahedral environment with three N atoms coming from three dcne- ligands, two nitrogen atoms from bpym and one oxygen atom from a water molecule. The extended structures of 1 and 2 are best described as dcne-bridged zigzag chains of MII ions running along the [100] direction; connections of these chains in the [010] direction, by the bis(chelating) bpym ligand, afford 2D structures. Compounds 3 and 4 are isostructural, and consist of discrete dinuclear units involving MN 4O2 octahedrally coordinated MII ions bridged by bis(bidentate) 2,2′-bipyrimidine and terminal dene ligands. Magnetic measurements for the 2D compounds 1 and 2 exhibit maxima in the χm vs. T plots (at about 4.5 K for 1 and about 20 K for 2) which are characteristic of weak antiferromagnetic exchange interactions between the high-spin metal centres. While the dinuclear iron complex 3 presents a similar behaviour (maximum in χm vs. T plot at 12 K), the antiferromagnetic exchange interactions are stronger in the copper complex 4. Fits of magnetic data for compounds 1, 3 and 4 with appropriate models led to J values of -0.6, -1.5 and -99.0 cm-1 respectively. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
Keywords
2
2 bipyrimidine
2
2 dicyano 1 ethoxyethenolate
bridged compound
chelating agent
cobalt
coordination compound
copper
copper complex
iron
ligand
manganese
metal derivative
nitrile
nitrogen
oxygen
polymer
polynitrile
pyrimidine
transition element
unclassified drug
water
angular momentum
antiferromagnetic exchange interaction
aqueous solution
article
chemical structure
geometry
infrared spectroscopy
J value
magnetism
molecular interaction
quantum chemistry
synthesis
X ray crystallography