Six-coordinate Copper(II) Complexes Derived from the Reactions of Bis(acetylacetonato)- and Bis(ethyl acetoacetato)-copper(II) with Some Bidentate Nitrogen Bases

Green-to-blue six-coordinate mixed complexes, Cu(acac)2(en) and Cu(etac)2(diamine)(acac=acetylacetonate anion; etac=ethyl acetoacetate anion; diamine=ethylenediamine, trimethylenediamine, 2,2′-bipyridine or 1,10-phenanthroline) have been isolated by the reactions of the respective parent β-diketonate with the corresponding diamine in dry dichloromethane. On the other hand, the reaction of Cu(acac)2 with en in the mole ratio of one-to-two in dichloromethane saturated with water has resulted in purple crystals of Cu(acac)2(en)2·2H2O. This compound has been shown by X-ray analysis to consist of a square-planar copper(II) cation, coordinated by two ethylenediamine molecules, and two planar acetylacetonate anions, the plane of which is not perpendicular to, but slanted against, the CuN4 plane. One oxygen atom of the anion participates in the N–H···O hydrogen bonding with an NH2 group of the ethylenediamine molecule, while the other occupies the axial position of Cu(en)22+ (Cu···O: 2.79(1) Å). Therefore, the compound can be designated by the formula [Cu(en)2]·(acac)2·2H2O. The water hydrogen atoms seem to take part in the hydrogen bonding with the anion oxygen atoms.