Copper oxalate complexes: synthesis and structural characterisation‡

Abstract

Six copper(II) oxalate complexes, namely {K

Synthesis, structure and magnetic properties of two bis(oxalato)cuprate(ii) salts with pyridinium type counter ions

“…The Cu( ii ) centre in 2 shows a square pyramidal geometry with four oxygen atoms (O1, O4, O5, and O8) from two oxalate(2-) ligands in the equatorial plane and one terminal oxygen atom (O7) from the neighbouring [Cu(C 2 O 4 ) 2 ] 2− unit in the apical position. The length of Cu–O eq bonds (Cu1–O6 = 1.957(1), Cu1–O7 = 1.934(1), Cu1–O11 = 1.935(2) and Cu1–O8 = 1.943(1) Å) are in good agreement to those in related Cu( ii ) complexes of 2,6-bis(4′-pyridyl-1′-pyridiniumyl)pyrazine 25 and aminoguanidinium; 26 the length of the Cu–O axial bond (Cu–O7 = 2.454(2) Å) is consistent with the ones in known aminoguanidinium 26 and potassium 27 salts and normal for a Jahn–Teller Cu–O bond. The bite angles of the bidentate oxalate were within the expected bond angles.…”

“…23,24 The packing of 1 shows strong interlocking between complex anion and cationic sub-lattices through a multidirectional hydrogen bonding network. The organic cations, ( 25 and aminoguanidinium 26 ; the length of the Cu-O axial bond (Cu-O7 = 2.454(2) Å) is consistent with the ones in known aminoguanidinium 26 and potassium 27 salts and normal for a Jahn-Teller Cu-O bond. The bite angles of the bidentate oxalate were within the expected bond angles.…”

Structure and magnetic characterization of some bicompartmental [N6O2] divalent metal(ii) complexes using bis(phenolato) ligands bearing two pendant bis(pyridyl) amine arms

“…The electronic spectra of Cu( ii )-H 2 L complexes, 2–4 , 7 and 8 obtained in CH 3 CN or CH 3 OH tabulated in Table 1 exhibit a general spectral pattern for the presence of a low energy single broad band over the wavelength region 640–720 nm. Although this spectral feature may indicate five-coordinate Cu( ii ) complexes in a distorted square pyramidal geometry (SP), 30,34,35 we still cannot exclude the possibility of a distorted octahedral environment. 36 This band, which is insensitive to the solvent nature (complexes 3 and 8 ), can be assigned to ligand field d–d transition.…”