Question

A starting complex reacts with H₂ to form a dihydrogen complex (n²-H₂) rather than a dihydride complex. a) Would a similar complex be more or less likely to form a dihydride if it contained more electron-releasing ligands? b) Would you expect the starting complex to react with ethylene to form a Dewar-Chatt type alkene complex or a complex with more metalacyclepropane character? Explain your reasing.

Answer 1

a) The dihydrogen complexes of metals are often referred to as nonclassical hydrides. The electron rich π basic metals are anticipated to split the metal bound dihydrogen moieties resulting in classical dihydride complexes. Along the same line of thinking, the electron deficient and less π basic metal would tend to stabilize a dihydrogen complex.

b) Starting complex would react with ethylene to form a Dewar-Chatt type alkene complex since binding an alkene to a metal often increases its susceptibility to nucleophilic attack.