Formal Sciences & Matter / Chemistry & Materials

Coordination Chemistry (Werner)

Alfred Werner showed in 1893 that a metal ion holds a fixed number of molecules around itself in a fixed shape, like six around cobalt at the corners of an octahedron.

For the cobalt compound CoCl3·6NH3, Werner proposed six ammonia molecules around the cobalt, with the three chloride ions outside; conductivity and silver-nitrate tests supported it, and the idea explained the green and purple isomers of related compounds. In 1911 his group split a cobalt complex into mirror-image forms and in 1914 one without any carbon, showing that handedness is not limited to carbon compounds, and in 1913 he became the first inorganic chemist to win the Chemistry Nobel Prize. Metal-organic frameworks, honoured with the 2025 Chemistry Nobel Prize, are crystals in which metal ions are joined by long organic molecules through this kind of coordination bond.