Conformational influences in copper co-ordination compounds. Part I. The conformation of the ethylene bridge in aquo-NN′-ethylenebis-(acetylacetoneiminato)copper(II)

A three-dimensional X-ray analysis of aquo-NN′-ethylenebis(acetylacetoneiminato)copper(II) has confirmed an eclipsed conformation for the carbon atoms of the ethylene bridge which are displaced, by 0·11 and 0·14 A, to the same side of the plane through the four donor-atoms of the chelating group. It is suggested that this is a result of the bending of the molecule consequent upon the adoption of a tetragonal pyramidal co-ordination geometry. Hydrogen atoms were located and the hydrogen-bonding scheme is revealed in some detail. Bifurcation occurs in the accepted sense, but in addition it is suggested that double interaction by a negative dipole, rather than a positive one, also takes place.