A tetranuclear copper(II) cluster structure [Cu4(OAc)4(OCH3)4] (50% probability ellipsoids) isolated after mixing Cu(OAc)2·H2O and azide 1 in CH3OH. Selected distances (Å): Cu1-O1 1.973, Cu1-O3 1.938, Cu1-O5 1.935, Cu1-O5i 1.924, Cu1-Cu2 2.958, Cu1-Cu1i 2.987, Cu1-O2 (opposite to Cu2 on the axial position; not shown) 2.586.