Copper(II) Melonates Cu3[C6N7(NCN)3]2·8H2O and [Cu(C2H8N2)2]3[C6N7(NCN)3]2·4H2O – Using the Terminal Cyano Group of the[C6N7(NCN)3]3– Ion for Complexation

. Copper melonate Cu3[C6N7(NCN)3]2 center dot 8H2O (2a) was synthesized by a metathesis reaction of potassium melonate with copper(II) in aqueous solution. A related copper melonate [Cu(C2H8N2)2]3[C6N7(NCN)3]2 center dot 4H2O (2b) was obtained from an aqueous potassium melonate solution containing copper(II) and ethylenediamine. The crystal structure of 2b was determined by X-ray diffraction analysis (triclinic, P$\bar{1}$, a = 6.8035(5), b = 12.6931(8), c = 14.9636(10) angstrom,alpha = 67.215(5), beta = 79.273(6), gamma = 87.206(6)degrees, V = 1170.17(14) angstrom 3). In contrast to already reported crystal structures of melonates copper ions are coordinated only to the terminal nitrogen atoms of the cyanamide functionality of the melonate anion. Both copper(II) melonates 2a and 2b were further characterized by FT-IR and 13C MAS NMR spectroscopy, TG/DTA, and elemental analysis. Whereas dehydrated 2a is stable up to 500 degrees C, 2b shows less thermal stability.