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 (L-1) and its two laria t derivatives, 15,15-dimethyl-16-crown-5 (L-2) and 15-(2,5-dioxahexyl)-15-m ethyl-16-crown-5 (L-3), have been prepared and characterized. The crystal s tructure of [Co(L-3)H2O)](ClO4)(2) has been determined by X-ray crystallogr aphy. The cobalt(II) ion is heptacoordinated with five crown ether oxygen a toms at the equatorial plane, a side arm oxygen atom and a water molecule a t the apical position. The coordination polyhedron of cobalt is a distorted pentagonal bipyramid with the average Co-O(crown) distance of 2.20(2) Angs trom.