F. Valach, N. N. Hoang, I. Lukeš:
"Structure of Disodium cis-Bis(iminodiacetato)-cobalt(II) Hexahydrate."
Chem. Pap.  50, (1996) 115-20

Abstract:

The crystal structure of Na₂[Co(Hida)₂]×6H₂O (Hida = iminodiacetato) contains discrete units [Co(Hida)₂]^2-, ions Na⁺, and H₂O mols.  The pseudo-octahedral coordination of Co(II) is created by four O atoms (the bond lengths Co-O are 0.202(1), 0.203(1), 0.207(1), and 0.210(1) nm) and two N atoms of two Hida ligands (bond lengths Co-N are 0.211(2) and 0.214(2) nm).  The cations Na⁺ are pseudo-octahedrally surrounded by four water O atoms and two carboxyl O atoms from the different units [Co(Hida)₂]^2-.  Crystallog. data and at. coordinates are given.