Complexes of 4- and 5-bromo derivatives of 2-(hydroxymethyl)pyridine with copper(II) and cobalt(II) salts. Synthesis and X-ray crystal structures

Abstract

Four copper(II) complexes ( 1– 4) and a cobalt(II) complex ( 5) derived from 4-bromo-2-(hydroxymethyl)pyridine ( L 1 ) or 5-bromo-2-hydroxymethyl)pyridine ( L 2 ) with Cu(NO 3) 2·3H 2O, CuCl 2·2H 2O and CoCl 2·6H 2O have been synthesized and their respective crystal structures studied. They show specific influences owing to the different kind of metal cations and counter anions, the hydration as well as the different position of the bromine substitution on both the coordination of the complex unit and the network structure of the crystal lattice. The Cu(II) complexes of L 1 are five-coordinate [Cu(L 1 ) 2NO 3]NO 3·H 2O ( 1) and [Cu( L 1 ) 2Cl]Cl·H 2O ( 2) species with distorted quadratic pyramidal and trigonal bipyramidal coordination geometries of the N 2O 3 and N 2O 2Cl donor atoms around the Cu(II), respectively. The Cu(II) complexes of L 2 are six-coordinate [Cu(L 2 ) 2(NO 3) 2] ( 3) and [Cu(L 2 ) 2Cl(H 2O)]Cl·H 2O ( 4) species with distorted octahedral coordination geometries of the N 4O 2 and N 2O 3Cl donor atoms. A distorted octahedral coordination geometry of the N 2O 2Cl 2 donor atoms is also found in the complex unit [Co(L 2 ) 2Cl 2] of the Co(II) complex 5 but showing the oxygen atoms of the chelating ligand as well as the chloride ions in a cis-position. Depending on the complex, water molecules and chloride anions are shown to act as stabilizing components of the crystal structure. The comparative structural investigation includes also known structures of the bromine-free ligand analogue 2-(hydroxymethyl)pyridine, illustrating the basic implication of the bromine substitution, mostly perceptible in the different modes of crystal packing.