Graham’s ammonium theory

In 1883, Jorgensen reported that tertiary amines form compounds analogous to metal - ammines. Because tertiary amines contain no replaceable hydrogen, Jorgensen s discovery eliminated Graham s ammonium theory (Section 3.1) from serious consideration, leaving the chain theory and Kekule s concept of molecular compounds in the running. In Werner s words, Kekule s dichotomy merely substituted a beautiful word for a confused concept . Therefore, for almost a quarter of a century, until displaced by Werner s coordination theory, the chain theory became the most popular and satisfactory explanation of metal-ammines. 

Graham s ammonium theory, 4 Gravimetry, 524-535 Group overlap integrals angular overlap model, 226 Grunwald-Winstein analysis, 504... 

The first real theory of coordination chemistry was developed by Graham in 1837. He argued that metal ions bonded to the ammonium ion by the displacement of one of the H atoms by the metal. This early model, however, could not explain the coordination of tertiary amines to transition metals, nor could it account for molecules such as CoCl3 6NH3, in which the number of NH3 molecules exceeds the valence of the metal. In 1871, Blomstrand adapted Graham s ammonium model by stating that because N is pentavalent, the ammonia molecules could form... 

He suggested that two hydrogen atoms, one from each ammonia molecule, were displaced by the copper atom, and he viewed the salt as a chloride of cuprammonium similar to the chloride of ammonium , thus explaining the strong retention of the ammonia in the compound. Graham s theory... 

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