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

Abstract

The crystal and molecular structure of LCO₂ [S₂P(OEt)₂]₂ (where L is a binucleating ligand derived from the macrocycle LH₂ formed by condensation of two molecules each of propane-1,3-diamine and 2-hydroxy-5-methylisophthalaldehyde) has been determined by single-crystal X-ray diffraction techniques at 295 K. The compound crystallizes in the triclinic space group Pī with two molecules in a cell of dimensions a 18.644(6), b 11.694(4), c 9.487(4) Å, α 84.99(3), β 82.61(3), γ 73.48(2)º. Automatic diffractometry has provided significant Bragg intensities for 2799 independent reflections and the structure has been refined by least-squares methods to R 0.054. The structure is molecular, consisting of discrete binuclear units LCo₂[S₂P(OEt)₂]₂. The two centrosymmetric molecules in the unit cell are crystallographically unique but essentially chemically similar. The two cobalt(11) atoms in each molecule are separated by 3.075(2) and 3.072(2) Å. Each cobalt atom is in an octahedral environment, with an N₂O₂ equatorial plane and two sulfur atoms of bridging dithiophosphate ligands in the axial positions. The Co-S bonds are the longest yet observed [2,680(3), 2.652(3), 2.642(3), 2.623(3) Å]. The cobalt(11) centres are high spin, with µeff 4.53 BM per cobalt atom. The macrocyclic ligand deviates slightly from planarity. The forces exerted both by the ligand L on associated metal atoms, and by axial ligands on the macrocycle, are discussed.