Metal Complexes of 2,6-Bis[(pyrazol-1-yl)methyl]pyridine: The Search for Aryl−Pyrazolyl Embrace Interactions as a Synthon for Crystal Engineering

The 2,6-py(CH2-pz)2 ligand was used to prepare metal complexes as follows:  [py(CH2pz)2](BiI3),
{Ag[py(CH2pz)2](OTf)·CH3CN}∞, {PtCl[py(CH2pz)2]}(BF4), {Cd[py(CH2pz)2]2}(BF4)2·[4,4‘-bipy]·0.5H2O, and {Cd[phen]3}2(BF4)4·[py(CH2pz)2]·5H2O (py = pyridyl, pz = pyrazolyl, and phen = 1,10-phenanthroline). The solid state
structures of each complex show that all five compounds are organized by noncovalent forces into complex extended
structures. Each structure has a common supramolecular organizational feature between the ligands of a cooperative
offset face-to-face π−π stacking and C−H···π interaction formed from both the pyridyl and the pyrazolyl rings that
is termed the aryl−pyrazolyl embrace. The systematic analysis of this synthon showed that the π−π stacking
component of the aryl−pyrazolyl embrace always involves rings of the same type.