Helical Transition‐Metal Complexes of Constrained 2,2′‐Bidipyrrins

Nickel(II), palladium(II), zinc(II) and copper(II) complexes of new constrained 2,2′‐bidipyrrin ligands (H 2 BDP) with a peripheral eight‐membered ring were prepared and examined with respect to coordination modes and conformation. Ni II and Pd II ions form mononuclear complexes with a distorted square‐planar N 4 coordination, which was determined for the palladium derivative by single‐crystal X‐ray diffraction. Zn II ions lead to the formation of dinuclear M 2 L 2 helicates, and for Cu II ions both coordination modes are realized. X‐ray crystallographic analyses reveal short M ··· M distances for the dinuclear helicates of Cu II and Zn II bidipyrrins and individually distinct packing patterns for both in the solid state. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)