Preparation and crystal structures of trans-bis(imidato)bis(1,2-diphenylethylamine)copper(II) complexes (imidato=5,5-diphenylhydantoinato and succinimidato). Particular boundary cases of coordination geometry and monodentate ligand conformation.

Two new copper(II) complexes, trans-[Cu(phent)2(R-diphenea)(S-diphenea)]·2CHCl3 (1) and trans-[Cu(succim)2(R-diphenea)(S-diphenea)] (2) (phent=5,5-diphenylhydantoinate, succim=succinimidate, and diphenea=1,2-diphenylethylamine) were prepared and crystal structures were determined. Nevertheless both complexes have the same diphenea ligands, 1 affords a distorted square planar [CuN4] coordination with imidate and amine trans-NCuN bond angles 156.6(2) and 161.4(2)°, while 2 affords a square planar [CuN4] coordination with both trans-NCuN bond angle 180.0°. Complex 2 was the first example of square planar [CuN4] complexes with 1-phenyl substituted ethylamine derivatives. Structural features are compared among 1, 2, and previously reported distorted square planar trans-[Cu(phent)2(R-phenea)(S-phenea)] (3) and trans-[Cu(succim)2(R-phenea)(S-phenea)] (4) (phenea=1-phenylethylamine) complexes. The structural features suggest that the [CuN4] coordination environment of 1 is distorted by particular edge-to-face arrangement of phenyl groups of amines and imidates which reasonably corresponds to the most and the second stable conformation of diphenea ligands with respect to rotation of two phenyl groups.