Spectroscopic properties and crystal structure of a tetraaza[14]annulene nickel(II) complex containing a strapped pyridine group

The reaction between a tetraaza[14]annulene (H(2)tmtaa) and 3,3'-(2,6- pyri dyldimethyleneoxy)dibenzoylchloride hydrochloride (Pydbc) led to the corres ponding compound (H(2)stmtaa) with a strapped pyridine group. The nickel(II ) complex (Ni(stmtaa)) has, been prepared from H(2)stmtaa and nickel(II) ac etate. The mass spectra exhibit the molecular ion peaks caused by the strap ped products, respectively. The infrared spectra reveal the strong stretchi ng modes of C=O in the range of 1645-1660 cm(-1). The structure of Ni(stmta a) has been determined by X-ray single crystal diffraction. The crystal bel ongs to a monoclinic system and the space group is C2/m. The nickel(II) is coordinated through four nitrogen atoms of stmtaa to form a four-coordinate square-planar configuration. The complex has a large cavity. The average b ond length of Ni to the four nitrogen atoms of stmtaa is 1.854(4) Angstrom and is very short. The displacement of the nickel(II) relative to the plane of the four nitrogen atoms of stmtaa is 0.010(1) Angstrom which is effecti vely coplanar. The H-1 and C-13 NMR spectra also confirm the structures of the strapped compounds.