Gravar-mail: Crystal structures of (1,4,7,10-tetra­aza­cyclo­dodecane-κ(4) N)bis­(tri­cyano­methanido-κN)nickel and (1,4,7,10-tetra­aza­cyclo­dodecane-κ(4) N)(tri­cyano­methanido-κN)copper tri­cyano­methanide