(2.089 Å) and 26c (2.084 Å), that are almost identical. The distances between the copper and the coordinative P atoms of the chelating diphosphine are quite similar for all three compounds (26a: ). These values are typical of a pseudo-tetrahedral geometry and match those of previously published copper complexes with related structures. The present chelating coordination mode is in contrast to the monodentate complexation observed for the heteroleptic phosphine silver complexes (see above).