Trihydrogen complexes

Later in the reporting period, an account of the first series of trihydrogen complexes was published. They were prepared according to equation (3). H-H 

11 Metal-Alkyl and Metal-Hydride Bond Formation and Fission 

Some species previously formulated as polyhydrides have been reformulated as containing dihydrogen ligands by the use of temperature-dependent 7, measurements. These include the first dinuclear 17 -H2 complexes, and The 

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The Act of 9.9 kcal mol i for the rate of H-atom exchange is the lowest measured among nearly 30 complexes (including the Ru species) and is consistent with a facile associative process [8]. Thus the H3 intermediate would be no more than 10 kcal mol i less stable than the H2/dihydride structure, suggesting that isolation of a trihydrogen complex may be attainable. 

The third example given in Figure 2 demonstrates an y -H2 complex of Ir from Crabtree s group that is stabilized by interactions with a terminal hydride ligand as a trihydrogen species. This internal ligand interaction presents an avenue for H/D exchange in H2/D2 mixtures under anhydrous conditions. 

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