Synthesis, characterisation and crystal structure of a cobalt(II)-hexamethylenetetramine coordination polymer

A novel one-dimensional zigzag coordination polymer, dinitrodiaqua-bis(hexamethylenetetramine)cobalt(II) was synthesised and characterised, and the structure was determined by single-crystal X-ray diffraction. The compound has a chain structure with each cobalt atom covalently bonded to two nitrate ions, two water molecules and two HMTA molecules, giving a slightly distorted octahedral geometry about the cobalt atom. Each HMTA ligand uses two of its N atoms to bond to two cobalt atoms giving an approximately bent Co-HMTA-Co configuration. Each chain is hydrogen bonded through OH center dot center dot center dot N and OH center dot center dot center dot O interactions with neighbouring chains leading to an overall polymer structure. Thermal studies show significant mass loss corresponding to the loss of the coordinated water molecules and the decomposition of both the nitrate ions and the HMTA.