The Synthesis, Infra-Red Spectrum, Room Temperature Crystal Structure and Hydrogen Bonding Network of Bis(2,2′-Bipyridyl)Monobenzoatocopper(II) Nitrate Hydrate. Investigation into the Role of Benzoato Coordination in the Vibronic Coupling Interpretation of Static Copper(II) Complexes

Abstract

The crystal structure of bis(2,2′-bipyridyl)monobenzoatocopper(II) nitrate hydrate, [Cu(bipy)2(O2CPh)][NO3]· H2O, (1) has been determined. The [Cu(bipy)2(O2CPh)]+ cation chromophore is basically five-coordinate, but with O(1), the second oxygen atom of the benzoato ligand, occupying the sixth coordinate position at a distance 2.696(2)A, from the copper. This suggests a (4 + 1 + 1*) coordination, involving a distorted stereochemistry, with a CuN4OO′ chromophore. O(2) is located at a distance 2.009(2)A from the copper. The two oxygens, O(1) and O(2), therefore occupy cis positions of the distorted octahedral coordination sphere and the coordinated benzoate is a highly asymmetric, bidentate ligand with ΔO = 0.687(2)A and Cu—OMEAN= 2.353(2)A. The two nitrogens, N(1) and N(3), located in positions trans to the oxygen sites, at distances Cu—N(1)= 2.148(2)A and Cu—N(3)= 2.058(2)A[Cu—Nmean/in= 2.103(2)A, ΔN1,3= 0.090(2)A] are slightly longer than the bonds to the two mutually trans related 'axial' nitrogens, Cu—N(2)= 1.987(2)A and Cu—N(4)= 1.977(2)A. The 'equatorial' angles α1, α2 and α3 have values 147.34(8), 93.29(9) and 105.39(9) respectively. The back-angle, α3, of 105.39(9)° is unique for a bipy complex, containing a carbonyl-containing oxoanion in such series. The asymmetric nature of the benzoato ligand is further evidence of the static nature of such complexes. The complex also involves a hydrogen bonding network, linking the O(6) of the nitrate to H(2)W of the water molecule at a distance 2.052(6)A and H(1)W to the long-bonded O(1) of the benzoato ligand, at a distance of 1.804(12)A.