TRANSMETALLATION REACTIONS OF TETRANUCLEAR COPPER(II) COMPLEXES .1. CRYSTAL AND MOLECULAR-STRUCTURES OF AN INTERMEDIATE AND A FINAL PRODUCT OF REACTION OF DI-MU-OXO-TETRA[CHLORO(DENC)COPPER(II)], (DENC = N,N-DIETHYLNICOTINAMIDE) WITH [ZN(N2S2)], (N2S2 = DIACETYL-BIS-HYDRAZONATO-S-METHYL-CARBODITHIOATE) IN APROTIC-SOLVENTSOF