The crystal structure of bis(NN-diethylethylenediamine)copper(II) dinitrate and the electronic properties of some square planar CuN4 chromophores

Abstract

The crystal structure of the red isomer of [Cu(deen)₂][NO₃]₂(1)(deen =NN-diethylethylenediamine) has been determined by X-ray diffraction using photographic techniques. The crystals are monoclinic, space goup, P2₁/n, with a= 9.76 (5), b= 12.81 (5), c= 8.24 (5)Å, β= 105.87(8)°, and Z= 2. The centrosymmetric CuN₄ chromophore is rhombic coplanar with Cu–N bond distance of 2.081 (5)(tertiary nitrogen) and 2.011 (5)Å(primary nitrogen). The conformations of the ethyl substituents effectively block the axial position of the CuN₄ chromphore and the nitrate ions exist as free ions in the lattice. The single-crstal electronic and e.s.r. spectra of (1) and of Cs₂[Cu(succ)₄]·2H₂O (2)(succ = succinimido), are reported, correlated with the X-ray crystal structures of the complexes, and suggest the presence of significant in-plane π bonding in (2).