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.

Graphical abstractThe formation of the above Cd(II)–ethylenediamine (en) species in aqueous solution has been determined by 113Cd NMR spectroscopy. In addition, two single crystal structures of [Cd2(en)5](ClO4)4 and [Cd(en)3](ClO4)2 were determined by single crystal X-ray diffraction. Based on both single crystal X-ray diffraction and Raman spectra, we observed that the cis-conformation of the bridging en is present in the complex, [Cd2(en)5](ClO4)4.Figure optionsDownload full-size imageDownload as PowerPoint slide