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

摘要

The compounds [Cu(pmda)(crea)] center dot H2O (1), [Zn(pmda)(crea)]center dot H2O (2) and [Co(pmda)(crca)(H2O)center dot H2O (3) were prepared and characterized by thermal, spectral and X-ray diffraction methods. In compounds 2 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 center dot center dot center dot O interaction reinforces the molecular recogniton crea-M-II(pmda) chelate. In contrast, the compound 3 exhibits an octahedral coordination, imposed by the 3d(7) 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'.