Complexation of cobalt(II) perchlorate with crown ethers. Synthesis, properties and structure of complexes of cobalt(II) perchlorate with 16-crown-5 and its lariat derivatives

Complexes of cobalt(II) perchlorate with 16-crown-5 (L1) and its two lariat derivatives, 15,15-dimethyl-16-crown-5 (L2) and 15-(2,5-dioxahexyl)-15-methyl-16-crown-5 (L3), have been prepared and characterized. The crystal structure of [Co(L3)H2O)](ClO4)_2 has been determined by X-ray crystallography. The cobalt(II) ion is heptacoordinated with five crown ether oxygen atoms at the equatorial plane, a side arm oxygen atom and a water molecule at the apical position. The coordination polyhedron of cobalt is a distorted pentagonal bipyramid with the average Co-O(crown) distance of 2.20(2)Å.