CRYSTAL-STRUCTURE AND SPECTRA OF BIS(2,2-DIMETHYL-1,3-DIAMINOPROPANE) COPPER(II) NITRATE

The compound Cu(Me(2)tn)(2)(NO3)(2) (Me(2)tn denotes 2,2-dimethyl-1,3-diamino-propane) was prepared and investigated by means of structural and spectroscopic (IR and electronic) measurements. The electronic excitation spectra are consistent with a CuN4O2 chromophore. The structure determined by X-ray crystallography consists of discrete Cu(Me(2)tn)(2)(NO3)(2) monomeric units, where the 1,3-diamine coordinates as a bidentate ligand through the nitrogen atoms. The copper(II) ion is surrounded by four nitrogen atoms of two in-plane chelating diamine molecules and two oxygen atoms of the nitrate groups in trans position. A centrosymmetric rhombic octahedral stereochemistry around copper pertains. The six-membered chelate rings attain the chair conformation. The inequalities in the Cu-N distances suggests second-order Jahn-Teller deformation while the elongation of the Cu-O bonds, resulting from weak covalent interactions with one of the oxygens of the NO3- anion implicates d-s orbital mixing. The tilt of the Cu-O bonds relative to the CuN4 plane and the short O...H distances suggest the existence of intra- and intermolecular hydrogen bonds, also revealed by the IR spectra. The principal stretching vibrations are assigned and discussed in the light of the determined structure.