Cd(II)–ethylenediamine mono- and bimetallic complexes – Synthesis and characterization by 113Cd NMR spectroscopy and single crystal X-ray diffraction

Formation of three Cd(II)–ethylenediamine (en) complexes ([Cd(en)n]2+, n = 1–3) in aqueous solution and in DMSO solvent has been established by means of 113Cd NMR spectroscopy. It is clearly shown that Cd(II)–en complexes form primarily in basic solutions. A correlation between the 113Cd NMR chemical shifts and the ethylenediamine (en) coordination number has been observed and discussed. Two single crystals with the composition [Cd2(en)5](ClO4)4 (1) and [Cd(en)3](ClO4)2 (2) were prepared from aqueous solution, and their structures were determined by single crystal X-ray diffraction. Cd(II) ions are coordinated by six atoms in both compounds, 1 and 2: via five N-donor atoms and one O-donor atom forming a bimetallic complex 1, and via six N-donor atoms forming a distorted octahedral monometallic complex 2. Raman spectra of complexes 1 and 2 also provide additional evidence that the cis-form of the bridging en is present in complex 1.