Bond lengths ethylenediamine complexes

A higher-ammine complex of copper(II) ion having more than four ammonia molecules within the complex is formed in an almost saturated aqueous ammonia solution. Distortion of the octahedral structure of the higher-ammine complex is pronounced compared with that of the tetraamminediaqua complex. The diamminesilver(I) complex has a much shorter Ag-NH3 bond than the Ag-0H2 bond within the aqua complex. Structures of bisand tris(ethylenediamine) complexes of Ni, Cu, Zn " " and Cd ions were determined and the bond lengths within these complexes were compared with those found for the aqua and ammine complexes. A brief discussion was made for the chelate effect of ethylenediamine molecules from the structural point of view. 

In this paper, we describe structures of the aqua and ammine complexes of some metal ions determined by the X-ray diffraction method, and variations of bond lengths within the complexes are discussed. Some results for structures of ethylenediamine complexes of metal ions are included, and a brief discussion is made for the chelate effect of ethylenediamine molecules. 

Table V. Comparison between the M-N bond lengths and thermodynamic data of ammine and ethylenediamine complexs. ...

In Table V are shown overall changes of enthalpies and entropies of formation of the ammine and ethylenediamine complexes of zinc(II), cadmium(II) and copper(II) ions, together with the lengths and frequencies of the totally symmetric vibration of the M N bonds. 

For the cadmium-ethylenediamine complexes, the lengths of the M-N bonds are practically independent of the coordination number of the cadmium ion. The values of enthalpy changes of each step of the reactions are also invariable (-14 kJ mol for each Cd-N bond), which are the same as that of the Cd(NH3) complex. Therefore, the Cd-N bond strength of these complexes are almost the same, irrespective of their structures. 

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