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(CH 2 -pz) 2 ligand was used to prepare metal complexes as follows: [py(CH 2 pz) 2 ](BiI 3 ), {Ag[py(CH 2 pz) 2 ](OTf)·CH 3 CN} ∞, {PtCl[py(CH 2 pz) 2 ]}(BF 4 ), {Cd[py(CH 2 pz) 2 ] 2 }(BF 4 ) 2 ·[4,4‘-bipy]·0.5H 2 O, and {Cd[phen] 3 } 2 (BF 4 ) 4 ·[py(CH 2 pz) 2 ]·5H 2 O (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.