Influence of the Counteranion on the Formation of Polymeric Networks by Metal Complexes of Hexamethylenebis(acetamide)

An investigation into the anion dependence of the network-forming ability of metal complexes of hexamethylenebis(acetamide), CH3CONH(CH2)6NHCOCH3 (HMBA), has resulted in the X-ray characterization of the compounds
[Co(HMBA)3][Co(NCS)4], 1, [Nd(HMBA)3][Nd(NO3)6]·2CHCl3, 2, [Co(HMBA)3][HgCl4], 3, and [Mn(HMBA)3][HgBr4]·3CHCl3, 4. The structures of compounds 1, 3, and 4 each comprise cationic frameworks formed by the
bridging action of HMBA ligands binding octahedrally to the cobalt or manganese centers and, in the cases of 3
and 4, the formation of tetrahedral HgX42- anions by transfer of the respective halide ions from Co or Mn to Hg.
Complete anion (NO3-) transfer between Nd centers is also a key factor in the structure of 2, which forms a
cationic 3-D network of HMBA-bridged octahedrally coordinated Nd centers with occluded [Nd(NO3)6]3- anions.
These types of inter-metal-anion transfer, with consequent complex counteranion formation, appear to facilitate
the network-forming ability of the metal−HMBA cationic arrays.