The Blomstrand-Jorgensen Chain Theory

Whereas Kekule disposed of complex compounds by banishing them to the limbo of molecular compounds , other chemists developed highly elaborate theories to explain their constitution and properties. The most successful and widely accepted of such pre-Werner theories was the chain theory,47 advanced by Christian Wilhelm Blomstrand (1826-1897)4 and developed by Sophus Mads Jorgensen (1837—1914).46 49 50 Although Werner s ideas eventually triumphed, this did not invalidate Jorgensen s observations. On the contrary, his experiments have proven completely reliable and provided the experimental foundation not only for the Blomstrand—Jorgensen chain theory but also for Werner s coordination theory. 

As new complex ions were synthesized, several bonding theories were postulated and rejected. The two most convincing theories, the Blomstrand-Jorgensen chain theory and coordination theory proposed by Alfred Werner, were debated extensively (a subject taken up in detail in Chapter 2) and it was coordination theory that eventually proved to be correct, winning Wemer the Nobel Prize in 1913. 

The Blomstrand-Jorgensen chain theory was the most successful of the early theories that attempted to explain the known series of cobalt ammonates. This theory combined trivalent cobalt atoms, divalent ammonia radicals, and monovalent chlorides to produce structures that accounted for some of the formulas, conductivities, and reactions of these compounds. However, when an analog of a critical compound was finally synthesized, the chain theory s prediction was wrong, and it started to lose favor. 

In the same way that the ammonia molecule was thought to have an overall valence of 2 and was represented as —NH3— in the Blomstrand—Jorgensen chain theory, water can be represented as —H2O—. Several compounds containing chromium(III), water, and chloride are given below ... 

Draw appropriate diagrams of compound (2) in the table, using (i) the Blomstrand-Jorgensen chain theory, (ii) the Werner coordination theory, and (iii) the present method of representing coordination compounds. 

Blomstrand s chain theory was adopted, modified and developed by his close fiiend in Copenhagen, Sophus-Mads Jorgensen (1837-1914) (7), who brilliantly defended it until Werner in 1907 - ten years after Blomstrand s death - synthesized c/5-tetraamminedichlorocobalt(ni) chloride (cis-[CoC 20 tl2) C ) (8). Then, with the words "Nu er striden afgjort" (Now the battle is over), Jorgensen graciously conceded defeat (9). 

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