The synthesis, crystal structures and infrared spectra of bis(2,2′-bipyridyl)mononitratozinc(II) hexafluorophosphate and bis(2,2′-bipyridyl)mononitratozinc(II) perchlorate: A comparison with existing [Zn(chelate)₂(OXO)][Y] and [Cu(chelate)₂(OXO)][Y] complexes of known crystal structure

In order to extend the number of [Zn(chelate)₂(OXO)][Y] complexes, with chelate =2,2″ bipyridyl, 1,10 phenanthroline and 2,2″-bipyridylamine and (OXO)^-=(ONO)^-, (O₂NO)^-, (O₂CCH₂)^- and (O₂CH)^-, the crystal structures and infrared spectra of [Zn(bipy)₂(O₂NO)][PF₆], (9) and [Zn(bipy)₂(O₂NO)][ClO₄], (10) have been determined. Both zinc(II) complexes involve a slightly elongated cis-distorted ZnN₄O₂ chromophore.The slight elongation contrasts with the more significant compressed cis-distorted octahedral CuN₄O₂ chromophore of the corresponding copper(II) structures. The Zn‐O bonds in (9) are 2.186(3) and 2.351(3)Å (ΔO0.165(3)Å), while the corresponding Zn‐O(1) and Zn‐O(2) bonds in (10) are 2.194(2) and 2.355(2)Å (ΔO0.161(2)Å), respectively. The mean Zn‐O bond distance in (9) is 2.269(3) and 2.275(2)Å in (10). Although the significant cis-distortion of the Zn‐O distances is comparable to the analogous Cu‐O distances, the ΔO values are notably smaller. The thermal ellipsoids of (9) and (10), which are slightly asymmetric (ΔO ≈ 0.16Å), are small and isotropic. Such differences reflect the spherical symmetry of the d ¹⁰ zinc(II) configuration relative to the nonspherical symmetry of the d ⁹ copper(II) ion.The ZnN₄O₂ chromophores of (9) and (10) are similar, indicating the isomorphous and isostructural nature of the complexes. Both complexes have a common back-angle or magic angle of α≈117°, in contrast to the bipyam complexes where the back-angle is much less at ≈105°, related to the conformation of the floppier bipyam chelate ligand.