Structural and Coordination Features of a Hydrated Nickel-Bromide Complex with Hexamethylenetetramine

The complex compound NiBr2×2(CH2)6N4×10H2O was synthesized and structurally characterized using X-ray crystallography, thermogravimetric analysis, differential scanning calorimetry, and infrared spectroscopy. The complex crystallizes in a monoclinic system (P21/c) with an octahedral nickel coordination environment, where Ni-O bond lengths range from 2.027 to 2.058 Å. Thermal analysis confirmed stability up to 150°C, followed by dehydration, HMTA degradation at 200°C, and framework breakdown above 300°C. DSC revealed distinct endothermic transitions. IR spectroscopy detected Ni-O stretching (450–600 cm-1), N-C vibrations (1300–1600 cm-1), and O-H stretching (3200–3600 cm-1), confirming hydrogen bonding interactions. These findings provide quantitative insights into the compound’s structural stability, thermal behavior, and hydrogen bonding network, with potential applications in materials science and catalysis.