Metal Chelates of N‐(2‐pyridylmethyl)iminodiacetate(2‐) Ion (pmda). Part II. Ternary pmda Chelates with M = Co,Cu or Zn and Creatinine as Auxiliary Ligand

The compounds [Cu(pmda)(crea)]·H₂O ( 1 ), [Zn(pmda)(crea)]·H₂O ( 2 ) and [Co(pmda)(crea)(H₂O)]·H₂O ( 3 ) were prepared and characterized by thermal, spectral and X‐ray diffraction methods. In compounds 1 and 2 the M^II coordination is of type 4+1 and approaches to a trigonal bipyramid (71.85 and 86.18 %, respectively) with rather linear N(pmda)‐M^II‐N(crea) trans‐apical angles, but with different longest coordination bond (Cu‐O(pmda) or Zn‐N(apliphatic, pmda), respectively). Both compounds are isotypic and one intra‐molecular interligand N‐H···O interaction reinforces the molecular recogniton crea‐M^II(pmda) chelate. In contrast, the compound 3 exhibits an octahedral coordination, imposed by the 3d⁷ electronic configuration of the cobalt(II) atom, and the crea‐chelate recognition involves the Co‐N(crea) coordination bond and one intramolecular ‘bifurcated’ H‐bonding interaction between one N‐H(crea) bond and one O(pmda) plus the O(aqua) atoms as ‘acceptors’.