Monomeric and Dimeric Copper(II) Complexes of a Pyrrole‐Containing Tridentate Schiff‐Base Ligand

Three copper(II) complexes of (L 1 ) – , [CuL 1 Cl] ( 1 ), [CuL 1 Br] n ( 2 ) and [Cu 2 (L 1 ) 2 (μ 1,3 ‐NCS) 2 ] ( 3 ), and two copper(II) complexes of HL 1 , [Cu(HL 1 )X 2 ] (X = Cl – , 4 ; X = Br – , 5 ), have been prepared and characterised [where HL 1 is the Schiff‐base ligand derived from pyrrole‐2‐carbaldehyde and 2‐aminomethylpyridine]. The removal of a chloride ion and deprotonation of [Cu(HL 1 )Cl 2 ] ( 4 ) to form [CuL 1 Cl] ( 1 ) worked well. However, attempts to protonate [CuL 1 Cl] with HCl to re‐form [Cu(HL 1 )Cl 2 ] were not successful. X‐ray structure determinations revealed that 1 is a N 3 Cl‐coordinated square‐planar copper(II) monomer [CuL 1 Cl], whereas 3 is a doubly end‐to‐end thiocyanate‐bridged square‐pyramidal copper(II) dimer [Cu 2 (L 1 ) 2 (μ 1,3 ‐NCS) 2 ]. The structure determinations on 4 and 5 showed that in both cases the copper(II) ion is in a distorted square‐planar N 2 X 2 environment, with the pyrrole NH remaining non‐deprotonated and uncoordinated. Variable‐temperature magnetic susceptibility investigations carried out on the end‐to‐end thiocyanate doubly bridged square‐pyramidal copper(II) dimer 3 showed that no magnetic coupling occurs between the two copper(II) ions; it exhibits Curie‐like magnetic behaviour.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)