N-Analogues of Metal Acetylacetonates: Bis(1,2,6,7-tetracyano-3, 5-diimino-3, 5-dihydropyrrolizinido)metal(II), (Metal = Fe, Ni, Cu, Zn); Crystal Structure of the Copper Derivative

The title compounds 2 contain new complex ligands. These compounds are formed from anion 1, which isomerizes in a metal-promoted reaction. An X-ray structure analysis was carried out for 2 (M = Cu). Complex 2 (M = Fe) can easily be reduced to the analogous diaminopyrrolizidine FeII complex.