THE STRUCTURE OF A POTASSIUM-COPPER COMPLEX WITH 6-MEMBERED MACROCYCLIC ETHYLSILOXANOLATE LIGANDS

The structure of K2([EtSiO2]6K2Cu4[O2SiEt]6) . 4n-BuOH, a novel mixed sandwich-like complex of K+ and Cu2+ with two 6-membered macrocyclic e thylsiloxanolate ligands, was established by means of X-ray study. The ligands have an all-cis configuration and a crown conformation. Four Cu2+ and two K+ ions form a planar hexagon sandwiched between antipara llel coaxial macrocyclic ligands. The K+ ions occupy two opposite apic es of the hexagon. The Cu2+ ions have square-planar coordination with four siloxanolate O(M) atoms, while the K+ ions, are coordinated with two O atoms of the solvating butanol molecules, in addition to four O( M) atoms. The electric neutrality of the whole complex is due to the t wo outer-sphere K+ counter-ions, each located over one of the two silo xanolate macrocycles, i.e., over the << decks >> of the sandwich and c oordinated with endocyclic siloxane O(Si) atoms, as in crown-ether com plexes.