Channeled Polymorphs of cis-M(CNPh)2Cl2 (M = Pt, Pd) With Extended Metallophilic Interactions

Two distinct polymorphs of cis-M(CNPh)(2)Cl-2 (M = Pt,Pd) were obtained under different crystallization conditions. One polymorph of each compound contains 3-4 angstrom-wide, vacant channels stabilized by a synergistic combination of extended metallophilic interactions and ligand pi-pi stacking, whereas the other polymorph contains no discernible void space and only isolated, longer metal-metal contacts. The channeled polymorphs are favored under faster crystal growth conditions, and face-indexing revealed that the growth axes are along the M center dot center dot center dot M chains. Although the channels extend the length of a crystal, they do not absorb solvent because of their narrow widths.