Of dihydrogen complexes

One family of porphyrin complexes that will be treated in the review, even though they do not contain metal-carbon bonds, are metalloporphyrin hydride and dihydrogen complexes. As in classical organometallic chemistry, hydride complexes play key roles in some reactions involving porphyrins, and the discovery of dihydrogen complexes and their relationship to metal hydrides has been an important advance in the last decade. 

In contrast to solid or gas phases, the formation of dihydrogen complexes in solntions is always a reversible eqnilibrinm ... 

TABLE 10.1. Second-Order Rate Constants (ft, 25° C) for Protonation of Transition Metal Hydrides with Formation of Dihydrogen Complexes in Solution... 

Fig. 5. Insertion of dihydrogen. Complex 12 is formed from the formal insertion of H2 into the Fe-S bond. The energy of complex 12 is relative to the energy of 1 + H2 and given in kcal mol-1.

The use of ethylenediamine and NH3 complexes in connection with JHD of dihydrogen complexes has been noted in Section 2-16 and the mechanism of solvent exchange with trans-[Os(en)2(i72-H2)S]2+, S = H20 and MeCN, has been studied.64... 

Metal hydrides were among the earliest fluxional compounds to be studied. The more recent discovery of dihydrogen complexes and stereochemical nonrigidity in complexes containing both hydride and dihydrogen ligands has provided one of the areas of most intense interest in DNMR in recent years. ... 

Reaction of dihydrogen complex 4 with phenylethyne gives vinylidene 5 as shown. No other reagents are required for this reaction. Propose a pathway from 4 to 5. [Hint The first step probably involves elimination of HC1.]10S... 

Particularly since the initial discovery of dihydrogen complexes by Kubas [48], the coordination chemistry of H2 has revealed rich complexity [49]. There is little information on the precise pathway by which hydrogen adds to coordinative-... 

After completing our work on C-H activation in 1985, we participated in the development of the chemistry of dihydrogen complexes by showing their generality and that they can be synthesised by protonation of compounds with a terminal M-H bond (Equation 1). ... 

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