The crystal structure of a binuclear cobalt(II) complex of a macrocyclic ligand

Abstract

The crystal and molecular structure of LCo₂Br₂,CH₃OH (where LH₂ represents the macrocycle obtained by condensation of two molecules each of propane-1,3-diamine and 2-hydroxy-5-methyl-isophthalaldehyde) has been determined by single-crystal X-ray diffraction techniques. The compound crystallizes in the monoclinic space group P2₁/c with two molecules in a cell of dimensions a 9.8723(5), b 16.891(1), c 8.0745(5)Ǻ and 102.06(1)°. Counter methods were used to collect the 2004 independent reflections above background and the structure was refined by least-squares methods to a conventional R-factor of 0.049. The structure is molecular, consisting of discrete binuclear units LCo₂Br₂,CH₃OH, containing two cobalt(II) atoms separated by 3.158(2) Ǻ. Each cobalt atom is in an identical pseudo-square-pyramidal environment, in agreement with the conclusion drawn from the electronic spectrum of the complex, with an N₂O₂ basal plane and a bromine atom coordinated at the apex. The methanol molecule is disordered and partially occupies the sixth coordination site of each cobalt, with a long bond of 2.503(9) Ǻ between the cobalt and the methanol oxygen atom. The central carbon atom of the propane-1,3-diamine residue is also disordered, occupying partially each of two positions.